Guide to Foundation Design | Column Footings

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Foundation Design

Foundation is the base of any structure. Without a solid foundation, the structure would not hold for long. We have to be very cautious with the design of foundations because our entire structure rests on the foundation. The job of a foundation is to transfer the loads of the building safely to the ground.

Laying of Column Footing Reinforcement | Foundation Design
Laying of Column Footing Reinforcement | Foundation Design

The strength of the foundation determines the life of the structure. As we discussed in the earlier article, design of foundation depends on the type of soil, type of structure and its load. Higher the load bearing capacity of the soil, the larger the load it could safely carry.

Foundations are basically divided into Shallow Foundations and Deep Foundations.

In this article, we are going discuss the step by step guide to Column Footing Design for a shallow foundation.

Reinforced Concrete Footings

Footing comprises of the lower end of a column, pillar or wall which i enlarged with projecting courses so as to distribute load.

Footings shall be designed to sustain the applied loads, moments and forces and the induced reactions and to ensure that any settlement which may occur shall be as uniform as possible and the safe bearing capacity of soil is not exceeded.

In sloped or stepped footings, the effective cross-section in compression shall be limited by the area above the neutral plane, and the angle of slope or depth and location of steps should be such that the design requirements are satisfied at every section.

Design Procedure of Column Footings | Foundation Design

Here is a step-by-step guide to Column Footing Design:

Column Footing Plan and Section | Foundation Design
Column Footing Plan and Section | Foundation Design

Step 1

Area required for footing

Square = B = (w+w1)/P0

Where,  Po = safe bearing capacity of soil

w1 = self weight of footing

w = self weight of footing

For Rectangle = b/d = B/D

A = b x d

Net upward pressure on the footing

q/p = W/A

Step 2

Bending Moment

Critical section for maximum bending moment is taken at the face of the column

For a square footing,

Mxx = q x B/8 (L – a)2

Mxx = q x L/8 (B – b)2

Myy = q x B/8 (L – a)2

Step 3

To fix the depth of the footing shall be greater of the following:

Depth from bending moment consideration

d = √(M/Qb)

where, Q = moment of required factor

Depth from shear consideration

Check for one way shear

Check for two way shear or punching shear

Critical shear for one way shear is considered at a distance ‘d’ from face of the  column.

Shear force, V = qB [ ½(B – b) d]

Nominal shear stress, Tv = k . Tc

Tc = 0.16√fck

Step 4

Check for two way shear

Critical section for two way shear is considered at a distance at a distance d/2 from all the faces of the column.

SF, V = q [ B2 – (b + d)2]

SF, V = q [L x B – (a + d)(b + d)]

Nominal shear stress, Tv =  V/2((a+d)(b+d)d) ——- {for a rectangle

Tv = V/4((b+d)d)         ——- {for a square

Tv = k . Tc

k = 0.5 + β > 1                       ; [Beta β = ratio of sides of the column

Tc = 0.16√fck

Area of steel, Ast = M/((σ)stjd)

395 thoughts on “Guide to Foundation Design | Column Footings”

  1. salam & hi,
    can u explain me … that the proceture to calculate total load of single story building + how to determine the area for (width of foundation , depth of foundation , thickness of block & number of off sets)…
    atiq….

    • Hi Atiq,

      Foundation design is a complex process. It depends on the total load on a particular foundation as well as the Safe Bearing Capacity of the soil.

      For example, a single storey building foundation with hard soil, where total load on footing does not exceed 300kN, a footing pit of 1M X 1M at a suitable depth upto hard strata would be sufficient. The pit would have a 6″ layer of PCC. On top of that, you would place a mesh of steel consisting of 8 rods each of 10mm diameter on both sides. Then place the column steel frame on top of it and tie the column bars to the steel mesh. Pour 6″ of concrete and let it harden. Then you can go for either tapered footing or block footing. Total thickness of block should be 15″, including the 6″ you of RCC poured earlier. So, for a single storey building whose load does not exceed 300 kN, and the soil strata is hard, the above given design should be sufficient.

        • Never observed any such failures in structures. So, am unaware of that. Maybe Google Search might help…

          Practically speaking, column reinforcement is embedded in many feet of concrete. Ensuing footing would be weak, but I doubt if it would fail.

          Cheers!

          • Yes! you are correct! If at all the workman ship does not satisfy , like the plumb of the column/building), there are no failures observed.

        • There is no failure but the eccentricity of the column reinforcement might be disturbed, thats why its important to tie the reinforcement after alligning to the center line.

          • Hello Ajaynder,
            When the eccentricity of the column reinforcement gets disturbed, it leads to structural cracks which results into structural failure. Structural failure does not just mean that “the structure would collapse” but it also means that the structural components like beams or columns in a structure are damaged which affects their strength considerably.

            Cheers:)
            BenzuJK

        • If u do not tie your column to the bottom mesh… then there will be joint failure (probably cracks in diagonal direction will arise that is shear failure) between column and the other member.

      • Hi Benz,
        I am bit tensed aftre readiing this article. My 2 story building (1300+1200 sqft) foundation design consists a mesh of with 8mm rods and column steel frame of 12mm. Is this is sifficient for this building? there are around 17 columns in the foundation with beams connecting all the columns. Reammy appreciated your reply on this ASAP.

        Sasi

        • Hello Sasi,
          8mm rods can be used for the footing mesh. The number of steel rods change with the thickness of the mesh. So the mesh being 8mm or 10mm is not an issue. It all depends on the load coming on a particular footing. The load on every column is different depending on which we calculate the total quantity of steel required. If your engineer is qualified enough then don’t worry, he will take care of it. Your building will be safe.

          • Hello Benz,
            Thanks for the quick reply. Just one more quiry. The beam size connecting all the columns are 30cmx20cm with avg span of around 4mts. Is it sufficeint dimension? just wanted to have second opinion. Also whether we need to extend the column pillars to to the roof level? My architect says its not required. Instead we can have 15 cm concrete belt with some additional rods running through out the plinth. Please advice.

          • Hello Mr. Kuttan,
            You can always keep in touch with me through my site. You can ask any questions that have regarding the construction field. Will try me best to help you whenever possible.

            Benzu

      • Dear Sir,
        I have 4 story building the foundation slab for each column is 1m2 and deepness is 70cm2 and beams connected in foundation each column 40x40cm with 6 each of 14mm rebar . it has totally 15 columns the size of the columns are 30x40cm each column has used 8 each of 16mm rebar and the soil of the fundation is strong. now please advice can i build one other story at the top of it to became 5 story. THANKS

    • yehh…If u consider G+3 bldg. go from top to bottom. first of all distribute the load of slab to the beam as per nature of slab i.e. if one way half-half or two way in trapezoidal & triangular section then beam will be loaded as VDL transfer this load to the supporting column .
      same procedure done for 2nd & 1st & Ground floor but while go to down word direction add upper respective floor load then you’ll get the total load on column

    • Generator Building is a place where heavy machinery is placed. Firstly, you will have to study the kind of machinery that will be used in the Generator Building. Only then can you estimate the load on the building. Once you know the average weight of the machines and the number of machines that your design supports you can then move on with the load calculations. More than the live load of the workers or technicians, consideration of the dead load of the machinery plays a vital in the design of Generator Building.

  12. i need details load, vibration and wind force calculation tank foundation as folloing:

    1.0 Foundation size = 8500 mm x 3200mm and need height
    2.0 need re-bar datails fourmula
    3.0 tank weight = 13 ton

    i hope my request will receive kindly consideration by you..

    Regards
    Ram

  13. Hello
    I am designing a G+1 Residential building that rests on a rock and the maximum column load I have got is 200KN. Since it is difficult to excavate the rock what is the possible solution and what minimum dimension of footing shall I use

  19. sir/madam,
    hi, I wish to know if in old structure foundation bolts and concret on surface damaged so to renew the foundation for steel structure. what can be done?

  21. Hi,
    We have one old building without columns slab rest on brick wall. It’s constructed before 10 years, now walls are formed cracks the building is in oil and gas plant no of times wall chipping and reconstructed for windows and Ac opening pls suggest the building is suitable for living or need to dismantled

  22. dear sir,
    i want to design a pre engineering structure on top top of r c c framed design. size is 120m x 31m. please help me to find out how many columns and footing size to find out. load of pre engineering structure is 60 ton.

    • Hello Labannya,
      Supporting a RCC slab on a 5″ brick is unsafe and not practical. It has to have a Column and beam structure above which RCC slab could be casted.
      The reason is that there are heavy chances that the brick wall might slip which would lead to the collapse of the structure. I hope would find the answer helpful.

  25. Sir,
    I would like to know the follwing for the calculation bearing pressure below a footing, to know whether the pressure is below the safe bearing pressure of soil.
    1. The unit weight of RCC below ground level to be taken is 25 KN/m2 or (25-15) KN/m2, where 25 is the unit weight of RCC and 15 is the unit weight of soil.
    2. Whether weight of soil above footing, i.e, weight of backfilling to be taken.

    • I didn’t understand your question. From what I could understand,

      Weight of backfilling is negligible. I won’t affect the footing much… 15 kN/m2 is not much, when a typical building load per square meter can reach above 1000 kN/m2. Even for a simple 3-storeyed structure, loads on columns routinely cross 500 kN/m2

      I believe a RCC design book would help you…

      Cheers!

  27. I want to replace 3- 6×6 bearing posts in the basement of a 3 story wood structure. They are currently sitting on 2×8 wood on an existing 1-2 inch old concrete slab floor. I want to put new footings under posts. I’m using 6000 psi concrete mix, what size footing width x length x thickness should they be, and configuration of rebar?

    • Hello Vijay,
      The column footing size taken for a three storied building depends on the spans i.e. column to column distance. Generally the size of the column footing is taken as 4’6″x5′ for 4m c/c

    • Four loads are to be considered in order to measure total load on the footing:
      1) Self load of the column x Number of floors
      2) Self load of beams x Number of floors
      3) Load of walls coming onto the column
      4) Total Load on slab (Dead load + Live load)

      Benzujk

  33. Sir, i constructed a single storey building, build up area is 900 sq.feet, the soil is hard and rocky, the depth of the footing is 6 feet, column footing size is 4’x4’feet, number of columns are 9, each column size is 12’x9′, rods used in column are four 16mm and two 12mm. plinth beam tie up with all eight columns one column is isolated, it is in parking area ( the rooms are 2 feet height compared to parking area ).
    i would like to know plinth beam is really required for that isolated column and how many floors can i construct on this foundation. please give your valuable opinion.

    thanking you,
    srinivas.

    • Hello Khan,
      One way shear means stress coming onto the structural members in the horizontal direction from one side. It generally causes cracks in the RCC members. Two way shear is said to occur when the horizontal stresses occur from either sides of the members causing it to crack or result in crushing of the structural members if not designed properly.

      Punching shear
      It generally occurs between a column and a footing. The column tries to punch itself inside the footing because of the excessive stress on it. This could cause weak joints between columns and footings and also lead to structural failure.

  39. thanks for the post. I want to design the reinforcement for upward (negative) reaction. (As it happens in Factory shed where both positive and negative reactions should be check.)

    need a technical help.

  40. If somebody don’t tie the column reinforcement to the mesh below then what will be the possible type of failures.What should be the design load to be taken for the footing design of a single storey, two storey, and 3 storey residential building ? I hope you can answer all my questions.

    • Hello,
      Tying the mesh to the column reinforcement keeps the foundation and column tied to each other which results in its stability and strength. Structural cracks might appear if one fails to do so.
      As i have already explained earlier, four loads are to be considered in order to measure total load on the footing:
      1) Self load of the column x Number of floors
      2) Self load of beams x Number of floors
      3) Load of walls coming onto the column
      4) Total Load on slab (Dead load + Live load)

      I hope I have made it clear.
      Benzujk

  41. Hi,
    i have to construct a house which has houses on both sides. what is the design for foundation and columns with out disturbing the sides of other houses. the critical situation is that i cannot afford space between the walls.

  42. Hi Benz,
    Thanks for the clarifications on earlier comments. I have my foundation ready now. Initially I planned for the red bricks for building the walls. Now changed it to cement blocks with MSand for plastering. What are the things I need to be careful while using the cement blocks with M Sand?

    • Hello Kuttan,
      The only care you will have to take while constructing your walls with cement blocks is checking the alignment of the walls. A wall with cement blocks is more prone to collapse as compared to the red brick walls if the alignment is not proper.

    • Hello Hari,
      Preferably, you should go for Framed Structures and avoid Load bearing structures. Load bearing structure is safe for a two story building but framed structure would be the safest. Though there is a little difference between the construction costs but keeping in mind the long term usage, one must go for Framed Structures.
      Also, the disadvantage of going for Load bearing walls for a two story building is that the walls get thicker and the inner space decreases. Since land has become so costly, going for a framed structure would be a sensible choice.

  46. Dear sir,
    in a school building some of the footings are coming over a sloping rock.here the strata is hard but the slope may leads to slipping of footing .so wat will be the possible solution that i want to follow?

    • Hello Fazil,
      The construction can be very well executed in a rocky terrain. You should keep one thing in mind while constructing on a rocky and slopy terrain; the rock which is being used for laying the foundation is not a loose rock, this could lead to structural failure. But if the rock is hard and solid but has a slope, then you need not worry about it. It would not affect the strength of the construction. I suggest, before you plan on initiating the construction, you should go for land surveying and get the important details which will help you figure out what kind of foundation is to be laid and if the construction is feasible in such a site. If you have any further questions regarding the construction, you are most welcome…. 🙂

  48. Dear madam/sir

    I strat next month my house work.house area is 1300 Sqft.kindly request to yoy please send footing and column sizes and reinforcement details and distance of every columns and roof slab thickness and reinforcement details. house size is 9m*12m

    Thanks and Regards

    M.Thirumurugan.

  50. Sir,
    As a general practice, we used to make Starter (of approx. 100mm ht.) for column formwork. But, from some expert, it is said that ht. of starter would be of 500mm ht. as per standard.
    Could you pl. explain the exact mathods.
    Thanks & Regards….

  54. please tell me the critical situation of footing designs like footing between two walls in which one is already constructed and other we have to construct with L shape

  55. Very Nice……………………….
    what should be the design load to be taken for the footing design of a single storey, two storey, and 3 storey residential building ?

  56. Hello,
    What are the general specifications for length of L for short columns.Because in some drawing I dont see the length extended inside footing.Suppose columns length is 3 m high then how much should be bended (L) inside footing.

    Regards

  59. I am building a 2 storey house in a land that was previously a paddy field. It was slushy / marshy land in which I filled with soil in 2001about 7-8 feet deep. Now i am planning to construct this house and do you think I need to go in for any specific deep foundations. One person suggested column foundation that goes to about 10 feet below ground. Another suggestion was well foundation. Please comment.

    Thanks,
    Kurian

    • Hello Kurian,
      Well Foundations are pretty outdated. You must preferably go for Pile foundations. Concrete Pile Foundation will be perfect in your case. Raft Foundation can also be used but since they are little more expensive option as compared to Pile Foundations, you could avoid them.
      Let us know if you have any more queries.

  61. Some references use net allowable soil pressure for the design, that is allowable bearing capacity less surcharge and the weight of the soil backfill but some does not consider deducting the weight of the soil backfill. When do we need to consider deducting the weight of the soil backfill from the allowable bearing capacity.

    Thanks!!!

  62. iam consturcting single story building at the edge of minor irrigation tank ,there is silty soil and room size is 24′-0″ x14′-0″ ,what depth ,size footing needed please reply

    • Hello Descravel,
      Isolated footings are of two types:
      1) Tapered footing
      2) Stepped footing
      Tapered footing which I guess you are referring to as sloped footing, is used in case of small constructions such as bungalows, duplexes or G+1 structures. The reason why it is used in smaller structures is that it is economical as compared to stepped footings.
      Stepped footings
      They are used in case of multi-storied constructions. Use of Tapered footing in multistoried buildings proves to be uneconomical.

  65. For seven storied residential framed structure with RCC columns 5.00 meter apart, which type of foundation would be required on moderate type of soil. If raft foundation is required, then what would be adequate depth of the raft ?

    • Hello Arun,
      You could go for an isolated footing even in case of a seven storey structure with RCC columns 5m apart. Raft foundation is used only in case of extremely weak soils. Isolated footing can be used even for a 10 storey building if the soil is moderately strong.

  66. I have booked one flat of a residential six storey building.The size of its colums is 12/16,its foundation is 7ft deep in hard soil,it has seperated colum footings.Is the building safe? Colums are cons
    tructed with 8 tmt bars(four of 16mm ,and four of 12 mm).Please help.

  67. Hi there,

    I am planing to construct my house on plot area of 20 ft x 20 ft = 400 sq ft, ground, and 400 sq ft. first floor, total Rcc area as per architact is 990 sq.ft aprox. I would like to know how much steel, cement sand and aggregates will be required so that I know the cost of material.

    Your earliest reply will be highly apriciated,

    Thanks

    Regards

    Dinesh Trivedi.

    • Hello Dinesh,
      The structural design depends on the building plan. WE cannot make assumptions. It is all calculated and required professional knowledge. Every project is different and has to be dealt separately. The quantities of sand, cement, steel and aggregates require a detailed analysis of the structural design. I hope what I am saying is making sense to you.

      Civil Projects Online has made things easier for you. It has launched Architectural and Structural Design Services at minimal costs. You can also receive expert advise.

      Architectural and Structural Design Services

  69. Sir, i want construct a G+4th storey building, build up area is 3973 sq.feet in 23’9″x158’5″ , the soil is not hard ,from entrence in right side 4’6″ wide open duct and left side 6’9″ wide
    passage. And, i want to provide 56 nos columns accrding to room(12’0″ x 12’0″) and their corner. and want also to provide 9.84″x17.71″(16mm dia) RCC column in outer wall. am i right or wrong
    thank you !
    S.rama

    • Hello Rama,
      The structural design depends on the building plan. WE cannot make assumptions. It is all calculated and required professional knowledge. Every project is different and has to be dealt separately.

      Civil Projects Online has made things easier for you. It has launched Architectural and Structural Design Services at minimal costs. You can also receive expert advise.

      Architectural and Structural Design Services

  70. In my house plan the contractor has drawn for the hall of 14 ft by 30 ft approx with 4 pillars at about 10 ft distance each and on other parallel side 3 pillars at 15 ft distance each and each pillar from foundation column has 6 no.s of 12 mm rods in 9″ by 12 ” column/pillar; Whether 12 mm rod vizag/TISCO make ok whether any special care to be taken in concealed beam on lintel or roof level required. How to cross check my plan if it is correct without defect………….lakshmanan

  71. hello Benz
    i want to know the procedure of machine foundation for 11kv isolator machine and transformer. . in some textbook they simply consider 0.12percent GA. . how the ecentricity calculation for this point load and hence moment. . also for mode of vibration and frequency check. .please guide me

  72. hello friends
    any one help me for design of pile cap. . i designed pile cap by embedded piles to pile cap and calculating the max reaction of pile per meter and hence moment with respect to ecentricity for this i designed steel . . is this procedure correct . . also in some books they will designed as slab by just considering as max BM respect to simply supported condition . . which is correct

  73. This is about ground floor column moments. We use column height from ground level to second floor in analysis of multi-storey bldgs. This results to column moment values at ground level. Now when we design the footing, we use this same value though the footing level is way below the ground level. Should we not neglect this moment as the ground slab and soil can provide rigidity and disperse column load moment when it reaches the footing level?

  74. dear benz,

    i am building a 3 +1/2 storeyed house om a hilly slope. The foundation mesh designed by my architect is 6′ x 6′ of 16mm rods and the columns are 9”x16”( 4 nos 16mm & 2 nos 12mm) size and beam size including slab casting is of 9”x18” ( 6 nos. 16mm ) The maximum beam length is 15’4”(c to c)’. All the beam placements are in a grid formation. Please let me know the following :

    1. what do you mean by tying the column end to the foundation grid? (My architect says the cloumn end needs to be just centered on to the grid and the footing pyramid built ( i.e there is no tying of the L-shaped column end onto the grid) How do you do the tying?

    2. Are the above column and beam dimensions and the reinforcement ok?

    3. Are these rectangular shaped columns have the same structural strength as a square shaped one of same size ( say 9” x 16” versus 12” x 12” )

    4. Does the placement direction of these rectangular columns ( i.e the facing of wider & narrower side ) need any specifications or can be faced as per the rooms partition requirements?

  76. Suresh :

    Hello sir,
    1. Can u tel me the purpose and necessary of provide tapered footing in residential building?
    2. Difference between tapered footing and block footing?

    Tapered footing and block footing are two alternatives that can be used for the same purpose.
    Tapered footing is sloped at all four sides whereas block footing is a single step footing.

    Isolated footings are of two types:
    1) Tapered footing
    2) Stepped footing
    Tapered footing which I guess you are referring to as sloped footing, is used in case of small constructions such as bungalows, duplexes or G+1 structures. The reason why it is used in smaller structures is that it is economical as compared to stepped footings.
    Stepped footings
    They are used in case of multi-storied constructions. Use of Tapered footing in multistoried buildings proves to be uneconomical.

  77. i am constructing a single story building (shops) and laid foundations with 3 x 3 feet column foundations. column had 4 x #5 size dia bars, we also had plinth beam. now the owner wants me to go for double story. what minimum should i do with the foundation or with columns to go for double column, help

  79. Hi..
    This is sharat
    Im a civil Engineer,
    SBC is calculated based on SPT test
    But is it the only criteria to decide SBC..
    If not so please explain in detail how to calculate SBC.
    Depending on type of soil how do to decide SBC??
    Pls reply me….

  82. why it is not necessary to do rubble soling beneath the footing if the same footing rest on the hard rock. and why some consultants suggest to do double layer of rubble soling beneath the footing?

  83. the idea behind to tie the column bars to its foundation reinforcement is to assure that the skeletal framework of a building will be acting as one, because reinforcement are assembled separately according to their usage it is ,by principle important/neccesary that this reinforcement should be secured properly to act effectively and actually serve its purpose nevertheless tieng this rebars is to avoid them from slipping from each other when subjected to excessive force/load

  84. Dear sir,
    I am planning to construct a G+1,where ground floor is 26’*22′ and first floor is 26’*36′ for that i have selected 15 pillers made of 16 mm rod square 04 nos and connecting beams of 12 mm rod square 04 nos.The ground condition is neither hard or loose.(medium).My selection is ok or not.can you please advise.

    Regards

  85. I find your column very useful.. my query is that I am a layman as far as the civil structures are concerned..

    We have a G+2 story structure and wanna construct one more floor. Floor size is 400 Inch X 400 Inch and it has a total of 13 columns of x section of 522 sq cms each (ie 9 inch X 9 inch)

    Is it advisable to go ahead with 3rd floor with existing structural strength ?

  87. Dear Benzu
    I want to know about following foundation Procedure.
    01.Machine Foundation
    a. Wt 123TN b. Suppliers Recommended foundation size 12m x 5m. Also Supply Moment x,y & z axis.
    c. 750rm.
    02. Foundation design of Fuel storage Tank 25m dia 18m Ht , Fuel Capacity 8000kl.

    Thanks with best Regards

  88. hi im john
    if you have a beam span of 8.50 to 10.0 mtrs. in a 15 storey building, what is the ideal section of the column on the ground floor?

    what is the ideal column size at 4th floor to support with a beam span of about 8.50 to 10m.?

    what should be the column size on ground floor if it has 8m span?

    what should be the size of a column at 4th floor if it has an 8 m. span?

  89. Hi Benzukj,

    When a foundation slab has a strip footing for exterior load bearing walls, can it be near or above a spread footings for columns. In other words can the spread footings for the columns be place deeper so it doesn’t interfere with the strip footings in the slab on grade foundation?

  90. Dear madam,
    in my three storied ratidential building(low land)-550 sq. ft area in one floor, 11 nos column all are 4-16dia bar(250X250mm), footing size 1.5mX1.5m with 12dia bar-200 spacing 1200 height, plinth & roof beams all are 250X2500 mm with 4-16dia bar.Is it safe? Please advise.

  91. how would you calculate storey shear and storey moment in kanis method of frame analysis(side sway type).I know its formula but my values are not satisfactory with my study material.Can you help me?

  92. Hello Sir
    I want to know the comparison between normal single/double slope truss of IS members and tubular/pipe sections for a span of 11 m and whose two ends supports on two column. Also give related books/journal/links information.

  93. Hello I’m trying to build a ground plus two shopping center on a 400 meters squared piece of land. I need a building plan, how much material i need? etc..,

    If you can assist I’m willing to pay for your services

    Thank you

  95. Hi Benzu,

    Thanks so much for your site!

    I need to build inexpensive support pillars for the landing gear of a Boeing 727-200 airliner which serves as my home (web site references below). I’d prefer a method which is both cheap and relatively easy to dismantle, but fully reliable and very long lived. My sense is that each of the two main landing gear need to support a maximum of about 380 K Newtons, and the nose gear a maximum of about 133 K Newtons. My subsurface soil is moderately firm clay, but my terrain slops significantly.

    At this time I’m focused on the left main landing gear task. It’s support pillar needs to be very roughly 2 Meters high and very roughly 3 Meters in diameter. The pillar tops must be concave (bowl shaped) so that the landing gear tires can roll a bit during an earthquake, to insure that no stress can develop, but return to the center once earth motion ceases (an anchor chain will become taut if the travel nears the pillar perimeter).

    Air is maintained in the landing gear struts so that they absorb shock such as from an earthquake. The inflation height of the struts is easily adjusted so as to level the aircraft, even if the support pillar’s height changes a bit over time.

    For the left main gear pillar, I’m currently considering a conventional circular concrete pad onto which an unconventional pillar is assembled as follows: Ordinary 10 cm diameter ABS sewer pipe would be stacked vertically one next to another, in an array which forms a 3 Meter diameter pillar shape, and held together with outer circular perimeter steel bands or similar. At least four steel rods would be inserted through the sewer pipes, each from the top of one side of the pillar to the bottom of the opposite side of the pillar, as diagonal members so as to prevent tilting of the pillar. The tops of the pipes would be cut so as to form the bowl shaped concave top. Each pipe would be filled with concrete and one centered reinforcing bar, or perhaps simply filled with gravel (or a combination, such as concrete fill for the center most pipes, where the tires normally rest, but gravel for the outer pipes).

    A steel or similar culvert pipe to house the array of vertical sewer pipes is a conceptually easier option, and I continue to consider that. However, 3 meter diameter culvert is expensive and somewhat awkward to transport.

    A conventional solid concrete pillar strikes me as likely quite expensive, and perhaps more difficult to assemble (due in significant part to the large reinforcing bar structure presumably required). It would also be far more difficult to disassemble. And my sense is that it would be far stronger than is necessary.

    I remain fully open to any ideas however – any concept which addresses the need most efficiently will ultimately win my heart. I’m an electrical circuit design engineer, not a civil nor structural engineer. So this is generally outside of my skills. In general, I prefer thoughtful exploratory approaches which yield improved efficiency over an unimaginative default to conventional design. However, if a conventional design simply proves to be the best option, then it would win my heart.

    I’d appreciate any thoughts or references you have, including the basics for the construction of the circular base pad.

    Thanks so much and regards, Bruce

    Hillsboro, OR 97123-9074

    http://www.AirplaneHome.com (http://www.AirplaneHome.com/Images/22Sep2011ImagesCatalog.htm)
    http://www.HikokiIe.com

  96. hi
    can you help me with our thesis?
    i’m 4th yr civil eng’g student
    our thesis title is “proposed design of special foundation considering the effect of mine blasting-induced ground vibration”
    we focus only on residential house foundation.
    what is the initial step we should do?
    how to design foundation considering blast loading?

    thank you for the response and this would be a helpful for our research.

  97. Dear Ben

    I want plan to start my G+2 home. please tell me about details please. building size 42’x20′

    1. column size
    2. no of rod
    3. rod size
    4. no of column (15 ok)

    please reply me…..

  99. hi, i’am second year civil engg student and i want to know what are the foundation details that are to be taken into account while selecting the type of foundation to be decided for a skyscraper

  100. hello, I would like to know is it acceptable practice to place an isolated footing in fill area ,I have 1.4 m fill over the existing ground level,or i have to embed it below the ground level

    • Hello Zahir,
      You shouldn’t place your isolated footing in fill area. You should cent percent prefer embedding your footing below the ground level to maintain the integrity and stability of the structure. If don’t do they, the structure is bound to develop foundation problems in futures. The most common one in this case would be sinking foundation.

      Be very careful while designing foundations. Remember that is the core of the structure. Let me tell you, foundation problems are disastrous and are very expensive to repair.
      Have you hear of the saying,”Precaution is better than cure”. Follow it. That is what we engineers should be doing.

      All the best!

      Also check out my articles on Sinking foundation. They will give you an idea about what kind of problems they create.
      Sinking Foundation – I
      Sinking Foundation – II

      • hello ma’am,
        all the information on the site and your explanation to all the difficulty for various questions have provided me more knowledge than any other source, thanks a lot for all the valuable information.

  102. khan :
    what is the difference between one way shear and two way shear?
    thank you

    hi benzu mam
    I want to know , how to fix the depth of isolated footing?
    Which are the factors that influence the depth of footing?
    Is there any codes that specifies the isolated footing depths?

  105. i want to design a singly reinforced T-beam by entering some data i.e. depth 300mm, width of beam -250mm, clear span-6.5mt, M-20, fe-415, bearing of simply support -250mm, please help me for solve me the problem and guide me.

  108. Hello Benz,

    I have a quick question on column footing. What happens if the column is not centered on the footing mesh? Does it compromise on the strength of the structure?

  109. Hello Srinivas,
    Firstly, you need a plinth beam to tie the isolated column because if you dont do so, it might result into bending of column resulting in collapse.
    4′x4′ footing size is pretty small. Your column steel design is good. If the column c/c are not more than 12′ than you could go for G+3 without any hesitation.

    Dear sir,
    Thanks for your above given suggestion for my query on 8.6.11.

    How can i tie the plinth beam, to the isolated coloumn. ( can i rise one more coloumn beside the isolated coloumn ).

    How much footing size required for three storied building.
    waiting for your valuable suggestion.

    thanking you
    srinivas.

  110. How & which combination shall be taken for foundation design in following given conditions :
    LOAD CASES REACTIONS (KN)
    V H
    Dead Load 16 6
    Dead Seismic R 2 4
    Dead Seismic L -2 -4
    Live Load 53 23
    Wind End Load -83 -21
    Wind Left Load -84 -43
    Wind Right Load -51 -7

  111. how do i make contact with you in order for you to assist me in my drawings for foundations with consultation. I’m willing to hive a meeting with you to discuss my requirements. Thank you

  114. Dear Sir,
    My house construction is progressing in Kerala, Kochi. I would like to know whether I can use kota stone slabs or like that materials for my wardrobes partitions and racks instead of going for ferrocement slabs, mdf etc. If so with kota stone or then how would be the connection with the wardrobes walls to insert this slab?

    Thanks
    Shamsudheen

  115. Hi Benz

    we are planning to built for industrial shed
    span 25 mtr widht, centre height of shed willbe 35 ft . and crane capacity will be 10 ton.

    request to inform what willbe civil footing size
    and column size for foundation ?

    Regards
    Girish BM
    +919552598092
    india

  116. Hi,

    I am planning for construction of 1st and 2nd floor on a building which is around 25 years old. Currently only the ground floor exists at this place. The current buliding has been laid out on foundation and not columns. As per my dad, the foundation is of 5 courses.

    Please let me know whether it is safe to go in with additional 2 floors on this building. Also request to know how many courses of foundation is needed for a 3 storyed building.

  117. sir,
    I design a three floor building column footing, 100cmx100cm size. 23cm rcc,then followed by 45cm to sloped. 10mm bar used for net. column size 23cmx35cm. this design is satisfied for the building.

  118. dear madam,
    how can i calculate size of columns, no. of columns for 15 x 50 plot. also i wanna know how much steel required for 3 floor building for the same area.
    plz suggest me suitable floor height taking all consideration such as ventilation, conditioning of room.

  121. Dear madam/sir,
    I am constructing R.C.C. building for 2099 Sq.ft. plinth area . Foundation work completed . All column tied with tie beam on ground and it is completed upto slab level.
    1) No of column= 19 nos.
    2) Size of column= 12”*12”
    3) Footing size = 4′ * 4′
    4) Dia of rod = 04 nos. of 16mm
    5) Foundation is 1.2 m below ground level and .90 m plinth ht. above ground level. Also we have three nos. span of length 5.5 m from c/c of column.

    Can i construct the building upto G+1 safely . Also can you suggest me as on thumb rule for beam size and the reinforcement dia and nos.

  122. hi
    my best wishes to u and many thanks to u for solving our problems after that must say that i am going to start a project of a business complex which would consist of 5 stories in the area of 520 sq meter, so i would like u to help me either by giving me a reference for civil engineering works or u may guide me to design and work on it, and must say that i am also a student of civil engineering and i live in noida up. and if u give me the refence around noida will be thankfull of u…
    regards

    • Hello Nick,
      We are launching a new business website where we would offer Architectural and Civil Engineering services at a minimum cost. I will get back to you only if you could wait for the next two weeks until we launch our website online.

      Cheers 🙂

  123. hi Benz,, Please can u advice me for the 23’span and 40′ long simply supported continuous slab without column support,two way slab need the how many concealed beams required with rebar detailand what will be distance c/c of re bars in both ways main/distribution.

    Regards,
    hrbmorai

  125. Hi

    for column, how much does it contributes to each level of a building when you are calculating the seismic weight of a building???

    for each level ive been tryn to calculate the weight which includes taking the weight(N) of the slab, beams, etc for each level and total them up to represent the weight of a particular level..but when it comes to columns im really not sure coz the column runs from the bottom to the uppermost of the building, so for each level how do we take the weight of the column???

  126. Hi,
    we are building RCC home on 1000sq fit area. I have got the construction layout and pillars design from professional. I am thinking of directly constructing slab over pillar without walls. but i have heard that slab will break if done in that fashion. What will you suggest? what should be the minimum slab requirement to avoid such incidence?
    thanks in advance

  128. Hi,good day, I need help.I am currently designing an extension of a church with 6 m. width and 11m long.it has a balcony design on top with the same size of the extension desired.Problem is,because of budget constraint i can’t make it to the soil test to know the soil bearing capacity.If in this case I wouldn’t know the design of its column and footing foundation.Can you please help me?Can you give a maximum design?…other problem is that I observe,when excavating i have notice that from the natural grade line and just excavated almost 2.00m,water is coming out.The proposed height of the front structural column is almost 10m,what will i do?can you please help me on this matter?I need it as soon as possible.Thanks and God Bless.

  130. Hi,
    My best wishes for launching Architectural & civil engineering business at minimum cost , looking forward for the same at the earliest. please let me know your website details …………….

  131. Hi,

    Kindly advice me about pile foundation, I’m going to build my own house 1100sq feet.
    In that area each builders are making difference pile foundations because of loose soil.

    E.g. –
    1. Bottom of the single Column
    Dia – 0.75 feet
    No of the pile – 3 or 4 or 5 piles
    Depth – 15 feet

    2. Bottom of the single Column
    Dia – 1feet
    No of the pile – single pile
    Depth – 15 feet

    Please advice me economic pile foundation methods

    Thanks

  132. Hi,
    can u explain me … that how we can done 6 foot foundation for 34 foot height and 3 foot by 3 foot watch tower (6×75 Angle of tower), please explain with drawing if possible.

  133. Is there any need to use steel reinforcement for wall like wall ties, mesh
    For fixing marbles to the wall there is any necessaty to fix it by using steel angle & bolts

  134. Helo Benzu,
    1) In a frame structure angle between RCC Column and beam laterally how much will be allowable Angle(?)?
    2) If the angle between RCC beam and column is more than 90 degree;is it wise to raise the building vertically upto 2/3 story (where the foundation is 3storied)?

  135. BenzuJK :
    Hello Mr. Kuttan,
    You can always keep in touch with me through my site. You can ask any questions that have regarding the construction field. Will try me best to help you whenever possible.
    Benzu

    Like this site very much!!!

  136. Hi,
    I’m constucting a gnd + 3 floor house on a 1200 sq ft plot. Right now as per plan from our engineer, we have about 12 columns, which are like 5 in a row on either ends and tow in the middle row. To be frant I really dont have much idea about the number of columns, load bearing capability, etc. My question is, are 12 columns sufficient for a 4 floor house on 30×40 sq ft. Secondly my engineer due to some vaasthu reason wants to live with just 10 columns, while getting rid of the 2 columns in the middle row. Is it something acceptable? My concern was that the two rows of columns are seperated by 23 ft. Is it ok to have it this way? Please advice.

  137. want to discuss about a plan …but can’t copy/paste here.how can I attached the plan that I can solve some confusion about the plan.
    Very helpful and informative your site is!
    Thank you.

  138. hi,
    plz, i want to know about portable houses
    and what are the things required for foundation of portable houses.I want to know its sizes and dimension

  141. Madam, I have gone through several of those queries and answers and found out to be very usefull, I have found out one of the problems is quiet similar to mine. I have already constructed g+1 and now planning for g+2. I have also received the soil testing results recently which suggested that my foundation should be at least 1.5 or 3m deep. The bearing capacity for 1.5m sand filling can give 6t/metresquare. and upto 3m deep foundation can give 20t/metresquare. Fortunately out of my 16 column 6 column are at a depth of 9 and half feet, 3 are at a depth of 10 and half feet and the rest are at a depth of 11 feet. All tappered foundation with 16mm and 12mm mesh alternatively tied and column size till ground level/plinth is 12x12inches with 4nos16mm and 2 nos.12mm diameter rods and after that raised in to 10x10inches column size till G+1. Column to column distance is 12x12feet. Foundation size is 6 inches with mortar and brick chips and and then mesh is laid over it,along with tied column structure and then again filled with mortar to about 6 inches towards the edges of foundation and about 12 inches thickness raised towards the column as tappered foundation. Madam I would request you to tell me if this foundation of my house can resist one more floor on my existing G+1. I would be gratefull to receive ur suggestion.

  143. madam how can i tie plint bean to an isolated column. actually, even one of my house column is isolated . although i m planning to raise two more foundation column side by side, but how to tie the i osolated column is the main problem. My house is G+1 presently. After raising two more column side by side and then resting on the beam, can it actually help me break the isolated column and then reinforce it with the other two, is the idea practicable, please suggest.

  144. thanks for this very important web site , your web site could be com pair with any engineering college.i have a question how to calculation about sterups in footing ?

  145. Hi,

    If I have a 20 m x 20 m building with a height of 42 meters including the basement floor and having a 1.50 m thick raft foundation, what should be the minimum level of the bottom of the raft foundation if it will rest on a non-cohesive soil having a bearing capacity of 250~300 kn/m²?

  148. madam,

    above FAQ are very useful ,

    i would like toknow how do design foundation for centrifuge equipment .(running at 1800 rpm,wt.7.5 ton.,1100 kg.m2

  149. Dear Mam,

    I am planning to construct a Three (3) storied building in 200 sq.yds plot and the slab area is coming to about 1600 sq.ft. I got the plan drawn by engineer, and he has shown 12 nos. columns to have big hall / bed rooms and column to column spacing is shown as 16 ft x 14 ft.

    I request you to kindly suggest the size of column, beam and slab thickness fit to this dimension and also the steel to be used for the same.

    Regards,

    K. Y. Rao

  150. I have a 2-storyed RCC house with columns and beams. The pillars are standard 9″x12″. Roof slabs are RCC, 4″ thick. The column spacing is about 12’x12′.

    I want to locate a water tank on the terrace within a 12’x12′ square. It will be a Syntex tank of base area of about 30 sq ft. I want to flll it up with about 8000 liters of water. Is it ok? Will the roof bear this kind of load? I am not a civil or mechanical engineer and find it difficult to calculate.

  151. hai mam
    am building a G+2 storey house in a land that was previously a paddy field. It was slushy / marshy land in which I filled with soil in 2001about 3-5 feet deep. Now i am planning to construct this house and my foundations sizes 1.2M wide & 0.3M depth (bars 10mm@175c/c top and bottom, stirrups 8@150c/c and am not going to go deep foundation i ill construct with existing ground level) along with the columns and walls (all around) my columns size is 0.5×0.15m (bars 8nos12mm)total 13 nos columns and span is like 2.5 to 3 meter and 2nos maximum span is 4.5m is it ok Another suggestion was well foundation. Please comment.

    Thanks,

  152. Hi,
    We are constructing 1400 GF & 1100 FF, This building comes up to roof level, total we have 14 columns 12 nos are 9” * 9” size and 2 nos are 1’*9” sizes, by keeping this columns sizes whether we go for second floor?,

    Pls advice us

    • Hello Sara,
      Please do not even think of considering going for a second floor construction with the sizes of the columns you have mentioned in the comment. The building will not be able to take the load and might result in structural failure.

  153. gd mrng
    my architect has given a very heavy metal beam work for my 2 storey building – residential cum play school. how do i know whether its ok or more than enough coz its exceeding my budget.
    plz help.

    • Hello Anupam,
      I feel you should trust the Architect. If he has given you a heavy design, it will cause no harm to your building. It would only be harmful if he would have given a lighter design. It would have been cheaper but disastrous. He is a professional, he will know better. So, I suggest that you should trust him.

      BenzuJK

  154. Dear Sir/Madam:
    I am planning to build a three-storied building (basement + ground floor + 3 floors) in Kerala. Right now, I want to build only the ground floor and add the three stories in the immediate future. I am drawing up the various estimates for my project. I would be very much obliged if you could kindly provide me with an estimate of the cost of each pillar. Hope you would oblige me.
    Thanking you.
    yours faithfully,
    Karthick

  155. Hi Benzu,

    Had a question on footing. After footing is done what could be the maximum delay in starting the column construction? My contractor has just did the footing with steel everything in place, but the column construction is not started.

    Thanks,
    Manoj

  157. Hi benzu,

    I need some clarifications, thought u could help me out.

    I am Mech engg working in EPC. I dont knw abt the civil foundations & pedestals.

    the Foundation drawings shows F1 to F30 and P1 to P46, wat r these….

    Help….

  159. Hi
    while designing rcc beam I found out the live load , dead load, floor load and self wt.of a beam per sq.m. My question is self weigt of rcc beam in kq/sq.m or kq/cu.m? Please decribe me

  160. Column and beam dimensions???

    Hi BenzuJK,

    I am designing a residential building for a university project, but can’t find any information on what size of column or beam to use.

    It is a G + 2 storey, RCC framed and brickwork building of size approx. 9.75m x 9.75m.
    Floor to Ceiling heights are kept at 3.65m (12’) for all the floors.

    3 Columns are positioned at 0, 4.55 & 5.2m c/c on East West direction and 4 columns are positioned at 0, 3m, 3.6m, 3.15m on North South directions.

    Size of Columns proposed are 12″ x 9″ with 6Nos of 16mm dia and size of Beams are 12″ x 9″ with 5 Nos of 12mm dia rods. (depth of footing is considered as 6′ below EGL.)

    Could you please comment if the column & beam sizes are reasonably okay.

    Thanks,
    Rama.

  161. I am constructing a house . in which on the right side its a joint wall of my neighbor. so putting a pillar close to the adjacent wall( pillar is not at the center it is on the side of the steel bed). but the problem is when we dug a trench suddenly water started leaking from the foundation of my neighbor house it the drainage line which got damaged . whenever they use their bathroom water suddenly leaks into our side ( Pillar) . But in spite of this our engineer told our neighbor stop using the bathroom for while and constructed the pillar.Now the pillar is built with cement and stones but my worry is water still seeped into the pillar may cause harm but my engineer tell us not to worry . technically what will happen to my pillar if water seepage from neighbor house doesn’t stop

  162. Hi Benzu
    Im a civil engineer and im trying my hand at designing practically for the first time though theoretically have tried at many times at uni. Im assuming that the first step is Load calculation where you arrive at the load each member would carry for the said building being designed. Do you have any format on excel which will facilitate the documentation & calculation of the same?

  164. Hello!
    I am new here and I am Civil engineer from Myanmar. I would like to know about foundation design of the gallon 500 small RCC over head tank. Height is 9 ft. I have a few knowledge with this design. That is why how can I calculate about the foundation design? Would you mind, please help me.

  165. hello BenzuJK ,
    can u help me , i want to make an emergency steel stair to a building with 4 storey about 16m height , i ll use 4 columns ( H steel section of 10 inch) , what is the good footing can i use it in this case( the base plate thick, the anchored bolt diameter&length ,the dimensions of concrete base for this case)

  166. Would you pls help me regarding two storied building construction process viz. foundation , main column , beam , wall , floor , roof etc. Here mentioned that soil is paddy land , area is 1400 sft.

  167. Plz let me know d most cost effective foundation for black cotton soil.I would like to construct a school with 14 rooms each with 17 X 23 ft (walls are not included). I think 2 story building save money so prefers that.Plz tell me other cost cutting methods for various stages.

  168. Madam, I want to know what should be the normal thickness and size of concrete foundation for G+2 building, Also i would like to know if it is safe to built G+2 on soil bearing capacity of 6 to 20 tonne/sqm.

    with regards
    Gautam

  171. It is observed that four columns of size 300×450 with 6-16dia and 2-12dia was laid with eccentricity 15cm above the plinth beam i.e., the column above plinth beam is placed 15cm away from the original column below the Plinth beam by bending the col. main roads above the plinth beam. But the column above the Plinth beam position is correct. How to rectify the defect. Please give suggestion.

  179. Hi Madam,
    I’m student of last year B.E.
    I like to design structure specially R.C.C. at this level i haven’t sufficient knowledge to do all things but i’m trying mine best.
    I am designing of multistory building. well mine question is regarding the foundation. In case of combine footing which kind of criteria i should have to kept in mind. Where can i adopt individual or combine footing. can u guide me. Thanks.

  181. What are the standard structural design requirements for a concrete foundation or pedestal supporting the BMU Steel Track anchored on the concrete pedestal by anchor bolts and steel clips?
    How to repair cracks on Concrete Foundation/Pedestal for BMU Steel Tracks? What are the causes of cracks or failures of concrete pedestal or foundation for BMU Steel Track?

  187. Sir i cam across this very site not quiet long ago. Please sir i am a student of civil Engineering 500 Level. Pleas sir can you help me out to be strong in structure? I really love to be a good and qualify Engineer. I don’t mine if starting the course fresh with you, to enable have more knowledge in this field. Sir below is my Email: ogbenistephenehizojie@yahoo.com. My Phone Number : +2348032657209. I we really appreciate a lot if you can help me to achieve my dream. Thanks

    • Dear Stephen,
      You can discuss and ask any questions you have on the blog and we will make sure that we answer them as soon as possible.
      This will also help in spread of knowledge among others as well.

      Look forward to seeing you visit the blog.

      Cheers 🙂

  189. Hi,
    Next year, I am planning to get my own house built. It is going to be a two storeyed one- 3 bedrooms (2 of them on the ground floor), 1 kitchen cum dining room plus the a bathroom, and a not-too-big living room (with a large French window). Now the issue is-I already have a one storeyed house (where i am living now) and I want to join this one with the 2 storeyed. So waht would be the best way to lay the foundation keeping the one storeyed in mind . I don’t have plenty of land area.

    The size of the plot is 175ft x 80ft (the house where I am staying at present itself has covered 90ft x 40ft ).
    N.B.- I WANT A SMALL BUT A LOVELY COMPACT HOUSE.
    Kindly advise,
    Thank you in advance,
    Deep

    • Hello Samuel,
      I am sure what you mean by a lap rod. There is something called a lap joint in beams. When two separate rods are placed side by side in a column or beam to extend the lenght of the rods, they form a lap joint.
      However, you have to be very careful with lap joints. There are several rules to be kept in mind.
      1) Make sure that the lap joint formation does not happen at the column-beam junction.
      2) The distance from where the lap joint should starts depends on the depth of the beam. For example, if the depth of the beam is 250mm, the lap joint should start after a distance of the twice the depth of the beam i.e. 500mm.

  192. We are building a house(apartment type) with four residential units of 700 sq ft each, two on each floor. The bldg should be able to construct another floor similar later.

    I saw the contractor putting 18 pits for column footing about 10 ft apart each. He had used the lowest concrete filling for about 4 inches. The other mesh work and column work has to start. He said the columns will be 30 x 22What should be the other dimensions of rods, and mesh for the footing and columns? Is his plan OK? He said he is using the rock-sand( not the river sand) inratio 1:6 I think.is itOkay?He said he is taking the guidance of a structural engineer. I have not met the engineer.

    • Hello Raju,
      There is some good news I would like to share with you.

      Today, Civil Projects Online has officially launched its Architectural and Structural Design Services offered through the website. In your case, you might need to consult with regards to reviewing the structural design of your building. Our experts go through the structural design drawings in depth and let you know if the drawings are upto the standard. They would also love to hear from you and answer all your questions.

      Take a look.


      Civil Projects Online now offers Architectural and Structural Design Services

  194. Ravi bhushan Mishra :
    First of all i want to thank you for solving/replying regarding the technical issues time to time asked by us – please provide me the detail in step by step for the constructional procedure of WBM road in hilly areas and what are the important points to be kept in mind during the work.
    I am waiting for your valuable reply.
    Regards,
    Ravi Bhushan mishra.

  196. Hello Benz,
    I buying a house which is being constructed now, the size of the building area is 17 x 40 feet.
    Ground floor, 631 sq.ft and first floor 731 sq ft is planned for construction. How many pillars and rods size are required for this type of plan and how much maximum span can be provided from pillar to pillar.

  197. Hello Benz,
    I am buying a house which is being constructed now, the size of the building area is 17 x 40 feet.
    Ground floor, 631 sq.ft and first floor 731 sq ft is planned for construction. How many pillars and rods size are required for this type of plan and how much maximum span can be provided from pillar to pillar.

  200. dear sir, i am building a 1565 sq feet house with 17 columns,12 x 4 nos rods and 10 x 2 mm rods (vertical bars), 6 mm tie bars are used,10 mm rods are used for footings with 4 x 4 feet, deep is 4 feet and is rocky area.pl tell me how many floors i can build. pl urgent

  201. Hi Benz,

    I am having 29′ X 60′ plot in Bangalore and started house construction with help of a builder. Builder proposed 15 columns – 15” x 9” 16mm 8 rods for each column, soil is bit loose mud. Currently builder is making 1’ 6” concrete footing for each column in 5’ x 5’ X 6’ (w x l x b). My doubt is 1’ 6” footing is sufficient of 3floors building?

  202. sir,
    What should be the depth of a footing for a G PLUS 4 CONSTRUCTION with 2000 sft for each floor. How many columns are roughly required. (Considering it to be hard soil.)

    • Hello Murthy,

      I strongly suggest that you follow the design procedures put up on the website. There is no such thumb rule for the number of footings. That would be very wrong. Every project is different and has to be designed carefully. I hope you got my point.
      Cheers 🙂

  203. Hi Benz,
    I am planning to buy a flat at a G+13 apartment complex. Soil foundation seems to be granite layer and they have pillars every 6′ or 8′ distance. Most pillars are of 3′ x 1.5′ and some are 2.7′ x 1′

    However, only few pillars have been built with 25mm iron rod, all other are mostly 16mm rod mesh.

    Do you think using 16mm iron rods like this can be reliable ?
    If you could categorize it as not-OK, OK, good etc. that will be really helpful for me.

    thanks
    sai

  204. Hi,
    I am constructing a 2-storey building with a basement, sunk 5′ below the ground level. The size of the building is 30×30. I have excavated 5′ below the basement level with a 1mx1m trench for footing which has hard gravel.(a) is this depth of 5′ for the footing enough? (b) what can be the dimension of the RCC column (c) can I use 12mm steel bars-8 nos? please suggest.

    • Hello Mr. Ahmed,

      This project needs further calculations for structural details. We have replied to your query on your email address provided. I hope that will be useful. We look forward to hearing from you.

  205. I m working on G+1 Sructure. I used coloumn of size 9″X9″, 9″X12″, 9″X16″. Ground strata is very good. I need to know the footing details like its pit size,depth, mesh size, dia and no of bars etc for each coloumn. plz help me out as soon as psbl. Thank you.

  206. steel reinforcement are not laid as straight rods on the slab crank are given, is it for alternate layers for compression and tensile strength improvement ? what should be the minimum concrete covered on the steel when concrete is poured.

  207. Hello Sir,
    We are constructing a four floor building with stilt floor for parking plus 4 floors and a pent house on a 2400 sqft plot, I would like to know the min and max steel bar size to be used by the contractor for column footing and RCC Columns and what shall be width of the footing and column.
    Note: each floor has a single 3BHK flat. Please reply.
    Appreciate your support with Thanks and Regards.
    Ahmed.

  209. Sir,
    I have a query regarding my house on a plot of 800sqft. The structure doesnot have a concrete roof (has asbestos sheet). It has nine concrete pillar but the tie beam is a raised one (the usual ones I see are under ground). 12 inch rods have been used throughout for all the pillars and tie beam. The structure is 14 years old. The plot is on a plain land. Presently I wish to develop my house into a two storeyed building with concrete roof. I want to know that will it be possible to develop it keeping the existing structure in place (with additions if any) ? Or do I need to raze the entire structure down and build it from scratch??
    Thanks and regards.
    Sankhadeep Saha,Kolkata.

  210. Sir,
    In continuation to my previous comment, I think the dimension o f the rods would be 12mm and not 12inch. Sorry for the error. Hope to hear from you.

    Thanks and regards
    Sankhadeep Saha,Kolkata

  211. Hellow sir
    We are constructing a building with columns. The starter bars were 10mm in diameter and now we want to use 12mm bars as the main bars. Is it possible? Can starter bars be smaller than the main bars? Thanx
    Best regards
    Lyn

  212. I am constructing a G+1 building measuring 9.5 M x19 M with column size 30 cm x 30 with 6 nos 12 mm rod with 8 mm rod for ring. Please advice, whether suitable or not?

  213. Dear Sir ,
    I am going to build a 12oo sq ft new 3 storied building on hard soil .
    Here the following constuctional structures are used for building 3 storied houses .
    Column base – 4 x 4 ft with 12 mm tmt ( 6 inches gap ) , 10 mm ( 4 inches gap )
    Column – 4 pieces 16mm or 6 pieces 12 mm tmt bars
    Beams – 2pieces 16mm + 2 pieces 12 mm tmt bars or 6 pieces 12 mm tmt bars with 16mm cranes in both .
    Please inform me , which type is suitable for a 3 storied building ?
    Which type of tmt bars shall I use in my house – cheap but best ?
    Thank you .

    • don;t go with out proper design because there is two situations in RCC 1.Under reinforced section and the other is over reinforced section if you provide over reinforcement the structure is not give any hints and suddenly collapse with out any warning signs where as under reinforced member will give you sufficient hints about its situation before collapse. this will get from design of the structure.. Best is Limit state method. u will get minimum thick of member and appropriated qty of steel

  214. Hello Sir,
    We are constructing a four floor building with stilt floor for parking plus 4 floors and a pent house on a 510 sqft plot, I would like to know the min and max steel bar size to be used by the contractor for column footing and RCC Columns and what shall be width of the footing and column.
    Note: each floor has a single 1BHK flat. Please reply.
    Appreciate your support with Thanks and Regards.
    Ahmed.

    • The Bearing capacity of the soil is not mentioned. The minimum diameter for footing is 12mm dia depth of footing not less than 15 inches using M25 concrete column minimum 12mm dia bar col. size 300x300mm is sufficient footing size is 5′-0″ 5′-0″ for 100Kn/Sqm bearing capacity

  215. Hello Sir ,
    what will be the column footing size , bar for a 3 storied house on solid hard soil ? which bar should be used in beams and columns ? the max distance between the columns are 12 ft .
    Thank you for your response .
    Warm Regards
    Amit .

  216. i am going to built a building of 82’6″x21’6″ & the total wall length is 327’0″.The staircase size is 10’0″x18’0″.i have planned to do 21nos.of column in G.F.of size 5’x5’x5′.pl kiendly instruct me how to do the cpolumn design beam design(Rod design with drawing).with all details.pl.guide me.

  217. For a roof slab measuring, 13ft x 22ft with a high ceiling of 17ft, how many columns and beams are required? Please let me know with dimensions of columns and beams.

    Regards.

    • Hello Sampath,

      Would you like to discuss your project in detail? I cannot tell you the number of columns. There are massive calculations to be done in order to determine them for structural safety.
      I look forward to hearing from you.

  219. Hello Ben ,

    I am to build a G+2 building by extending and renovating a single storied building . The existing building is with 30×30″ footing with 8mm rod , 4 pieces 12mm rods in columns ( column to column distance is not more than 11 ‘ in the building ) , 4 pieces 12 mm and one 16mm rod as crane in the tie beam on the ground ., wall 5″ brick . But there is no beam under the roof .
    Now I want to extend it to a G+2 building with larger rooms , balcony etc but don’t want to demolish the existing building ( may break some parts of roof , floor ; but will keep the building ) .

    Is it possible ? Please guide me ! I am really anxious .

    • On a G+2 building, load on a typical column could go upto 50 tonnes, sometimes higher or lower depending on the building plan, column to column distance and other factors… That would mean columns of atleast 9″ X 15″ using M20 grade concrete or higher… with a minimum of 6 bars of 12 MM. Footing size would depend on the bearing capacity of soil. For a good soil of 25 tonnes/square meter bearing capacity, the area of a typical footing would have to be Load/Bearing Capacity = 50/25 = 2 Square Meters.

      So, I believe you current footing size and steel would be inadequate for a G+2 building. It would be very unsafe. Please don’t do it.

  221. in my house construction, instead of 1:1.5:3 proportion of concrete, 1:3:4 concrete is put without proper supervision. Now only footing work is done. site is 30×40. house is still+2 floors. there are nine columns of size 9″X15″ and 3 columns of 9″X18″. I am worried about the strength of concrete in footing. is it sufficient? Pls help me.

    • Hello Ramakrishnaiah,
      How is it even possible to know whether the footings are sufficient? A structural designer would assess the total load coming onto the footings, then determining the size and depth of footings based on load and safe bearing capacity of soil. There is no way for me to ascertain any of that.

  223. if any possibility of unequal settlement due to filled earth what is the requirements needed?
    and what is the difference between floating slab at plinth level and basement

  225. Hello Sir, could you advise me on the minimum number of beams that could carry a slab in a room of 66 square meters if there are eight coloumns distributed right round along the walls? Note that the slab would serve as the floor of a classroom for thirty children of 12 years of age each.

  228. This website is very helpful, thank you very much,
    I have one question please, what type of footing is best for residential building G+1,2 and 3
    Tapper or Flat footing
    Best regards

  230. Hello sir,
    i’m designing a building 50’x90′(G+2) so can u plz advise me that what should be size of foundation(lxbxh) & also what should be depth of foundation below G.L?

  231. Dear sir,
    I have one request, that is I have 26’X65′ site, the soil is black cotton soil (I mean paddy cultivation land), I would like to construct three storied residential building at the size of 20’X35′ can u arrange foundation design parameters please.

    Thanking you

  232. Respected Sir
    I have plot of land 50×80 feet having steep terrain in lose soil. I want to construct 4 storied building. Kindly help me foundation design. Thanking you Sir

    Regards,
    Joy Koyu

  233. Dear Chanti,

    The process of constructing any house will be first to prepare a drawing, it should contain the size of the building such as Hall, Bed room, Kitchen, etc.,. The roof height and the number of floors also should plan. The details should be given to a structural engineer to do the design and fix up the column position to transfer the safe load to the foundation. Soil testing report also very important to decide the type of foundation and depth of foundation. Please consult a Structural Engineer to design the building and live safely. self medication will kill the people similarly it is not advised to construct a building with out involving the professionals.

    Thanks & Regards
    A.Chellappan, ME ( Str )., MIAStructE.,
    Registered Structural Engineer
    BCC/BL-3.6/S.E & Member of IASE M-127

  234. Dear sir
    Suggest me a number and size of piller n beam to build a duplex in 20*30 site . soil is having good strength please give me full detail like length n type of pillar n dista between them.

    • If it is an RCC framed structure, the walls don’t carry any load. But for protection from natural elements like rain, summer heat and some insulation from winter cold, it is recommended to build 9″ thick external walls. Internal walls are partition walls, so a 4″ thick wall should suffice.

  236. Good day Sir
    We are constructing a steel undercover storage 39′ 5″ x 98′ 5″. Consisting out of 16 columns (8 front & 8 back) 19′ 6″ high with corrugated roof. Please advise the size plinths we need to cast for the 4 hold down bolts of each of the I beams (8″ x 6″ 8mm thick) used for the columns in the construction. The soil where this storage area will be erected contain no rock content. A forklift will be operated on the floor with up to 20 ton loads. Please advise the reinforcement required for the floor and the distribution thereof. Thank you.

  238. Dear Sir,
    We have faced a problem that our civil foundation diameter is 50 mm less than that of our equipment base plate outer diameter.
    Please advise what can be done to eradicate this problem.
    Regards,
    Amit Mitra

  239. Sir, i have to construct a framed building in a soil of SBC of 100Tons/m2. The load from the coloumns is approximately 50Tons/m2. The footing size calculated is nearly 0.50m2. Is is practically possible. Please inform the minimum width of footing if any.

    • Your assumptions are wrong. Never in my life have I seem any design of foundation with SBC of 100 Tons per square meter. Even the hardest, stable, rocky soil is assumed to have a SBC of 35 Tons per meter square. That is the maximum.

      The minimum size of any foundation, even for a 1 storey house, should be 1 square meter. That is the minimum. You go up from there…

    • There will be no danger to the structure if the design is good. If you have determined the safe bearing capacity of the soil, and know the maximum load on the footing, then you can determine the size of the footing that has to be used.

      There might be some differential settlement between different columns, but not enough to be a major issue.

  242. sir,
    Depth of Footing 6′, footing Mesh size 5’x5′ of 12mm rod, column 16mm 4nos and 12mm 4nos. column c/c maximum 4mtr. soil not hard but river course soil. is it suitable for G+3 ?
    I’m confussed

  243. I wish to construct 30ft*25ft size first storey on the 40ft*25ft ground floor building. Ground floor is constrcuted without pillars.
    1) how do I determine if foundation is enough to rasie first floor without pillars
    2) possibility of laying pillars now.

    • This job would not be possible without a trained structural engineer. Please do not take the risk of doing it yourself. The consequences could be dangerous.

  244. I am planning to construct G+2 on a 30×40 plot.it was a agriculture land filled with loose soil for surface levelling.Would like to know if 9 columns 12″×9″ at a c/c distance of 8.5 feet with a footing of 3 ‘×3′ at a depth of 5’ is enough to with stand building load.

  245. sir i want to know that can a rcc slab 3.05m x 5.80m size 15cm thick reinforced with 10mm dia bars 15cm c/c spacing both in main & distribution is already casted . Now i want to construct first storey above it . accoding to my design i have to cast a 23cm thick brick wall 3.05m long 3.60m high above that rcc slab of ground floor . there is not any beam below that slab to carry load of brick wall . Can i construct that wall with giving a beam 23cm wide & 15cm thick with 4 bars 12 mm dia and 2 bars 16 mm dia to withstand load of that wall & slab above it .

  247. Sir, One of civil Engineers suggested that house with Ground Floor and First floor can build without coloumn & Beam. Floor area is aprox 1600 Sq. Ft.(2 BHK). Ground is hard. Red stone is using for foundation and wall. Wall width is 9 inch.
    He suggest that putting one beam at ground, next beam at plinth level and third beam at lintel level and giving slab load on wall. Pl suggest about this design.

  248. dear sir,
    i would like to construct a home at kerala ekm dist near munammbam. my plan consisting 150m2 plinth area and 90 m2 for f floor , the soil is ordinary black soil the maximum span of the wall is 4.5 mtr,height 3.1 mtr and using brck/block wall thickness 24 cm after plastering, if i am go through rcc framed structure what are the size of column,and footing slabs, depth of the footing, depth of the footing slab,and ground beam size,and its rebar sizes, if providing lintel belt, is it required top beam connecting all the columns below the rcc slab . awaiting your valuable reply
    with regards
    manoj

  251. I am constructing a residential G+1 building. I have given the work of construction to a contractor. Due to soil having lower bearing capacity, my contractor advised me to bore well upto 10 to 12 ft. and then fill the same with white sand. He told that this process is called ‘sand piling’ and it will increase the bearing capacity of soil.
    My question is- Whether this ‘sand pilling’ is sufficient for G+1 building having area of (1200+1200) sqft.? Kindly reply.

    • I cannot answer that question since I do not have all the details of the site type and its topograpgy. I would recommend that you consult a local structural engineer to help you out with calculations. It is a big risk you are taking.

  253. I am designing a rc footing for a 500cm bolted steel resevior tank raised 15m high on 9 steel columns. I have the geotechnical report, the calculations for the weights of the tank materials and the water when full, I need advice on how to proceed?.

  254. I have to erect one Billboard 80′ high 4′ dia M.S pole and V-shaped displays 40’x40′ each with a distance of 20′ on the rear end of V.Approximate weight in total 34 tonnes.The SBC is 30 t/mt and wind loads around 44m/sec.This is in India Hyderabad.The pole will be immedialely adjacent to the R.C.C retaining wall and the foudation has to be in the opposite direction away from the retaining wall which runs 30′ under natural ground level.

  255. Please explain we need to construct another storey over a house size 65’*22′ already rooms constructed are smaller then the rooms we will construct on the first floor, kindly explain how many columns we required

  256. Hi,
    can anyone explain how the construction goes for a footing of size 5′ x 5′ , depth – 18″ with dia of 10mm steel at 5″ double mat. what is this double mat in this footing construction??

  258. Dear Mr.BenzuJK
    My architect proposes 12 Nos column in 4×3 grid (4 columns along 40′ side of plot and 3 columns along the 30′ side of the plot). Of the 12 columns, 6 Nos of columns are of 9″x9″ on the outer right & Back sides of the 40’x30′ plot size balance 6 Nos columns are 9″x12″ (3 columns of the left side and 3 nos of the center line of plot. The Reinforcement size suggested is 12 mm – 4 Nos with 6mm stirrups/ties @ 200mm c/c distance. I plan to build GF + 1 Floor presently and add one floor later.
    The column raft is 4’x4′ for all columns. Thickness of raft-slab not givecn by architect, reinforcement details of raft not given by architect.
    1st floor and roof Slabs planned to be 100mm thick.
    Is the building design safe? I have asked the builder to hold construction till I get some confirmation.
    Thanks in advance for any guidance.

    • There are many factors that determine the size and reinforcement of columns and footings. There is no simple answer. There is a procedure to calculate axial load and bending stresses on columns. Once you know that, you decide on the strength of concrete you would want to use. Depending on that, you can design the columns.

      Footing size and steel depends on the safe bearing capacity of soil. Same thing, no simple answer.

      What your architect has proposed seems safe from my experience for a G+1 building. But there are some unknowns too.

  260. Sir,
    I have started my two storey house, The plot was Excavated about 1.5m from Original ground level. The problem is that the strength of the soil is reduced. It is see that red earth is dust type. What are the provisions i have adopted here for a good foundation?

  261. We have 12 pillars of 12mm rod,three floor building,and only 2 of the sides supporting the building giving it the structural strength. Is it safe or unsafe ???? Can you please reply fast!!

  263. sir,I have a liittle chalenge about a one story residential building in my care.As at the time we started,we only have money to buy few 12mm which we used for both the mat and starter bar of all columns(4Y12) now i was advice to use 16mm and I have cast the foundation part of the column.Will it be advisable if i lap the 12mm starter bars with 16mm.Pls sir enlighten me.

  264. My3 storey house having foundation dept 1.5 meter dept from natural ground. The rebars is 16mm 4 inches spacing and 1.5 meter per side(1.5m x1.5m). The thickness of the foundation is only 18 inches but having a tie the beam after 1.5m dept with 6 rebars of 16mm sizing 10inches by 12inches the the beam. Is this can hold my house when intensity 7.5 earthquake?

  265. I have started my two storey house, The plot was Excavated about 1.5m from Original ground level. The problem is that the strength of the soil is reduced. It is see that red earth is dust type. What are the provisions i have adopted here for a good foundation?

  266. Dear Mr. Benzu JK
    I have 4 story building the foundation slab for each column is 1200mm2 and deepness is 70cm2 and beams connected in foundation each column 40x40cm with 6 each of 14mm rebar . The area is 180 square meter and has totally 15 columns the size of the columns are 30x40cm each column has used 8 each of 16mm rebar and the soil of the fundation is strong. now please advice is the biulding safe.

  267. I have started my two storey house, The plot was Excavated about 1.5m from Original ground level. The problem is that the strength of the soil is reduced. It is see that red earth is dust type. What are the provisions i have adopted here for a good foundation?

  268. y3 storey house having foundation dept 1.5 meter dept from natural ground. The rebars is 16mm 4 inches spacing and 1.5 meter per side(1.5m x1.5m). The thickness of the foundation is only 18 inches but having a tie the beam after 1.5m dept with 6 rebars of 16mm sizing 10inches by 12inches the the beam. Is this can hold my house when intensity 7.5 earthquake?

  271. what is the effect of constructing isolated FOUNDATION at DIFFERENT ELEVATION for same building? or
    what is the effect of having DIFFERENT LENGTH FOUNDATION for same building?
    will STIFFNESS be an issue?
    what about Lateral force or EARTH QUAKE?
    what is the remedy for this type of problem?
    PLEASE recommend me reading material on this topIC
    Thanx!!!!

  272. Dear Sir,

    We constructed a G+1 building. Length 78ft, Width 27ft to 15ft (Land is not rectangle, front is 15ft, back is 27ft).

    Now I am planning to build another story (make it G+2). But my dad is not happy with it since he constructed it for G+1. Following are the details of the building, please give me a solution whether can i go for an additional story.

    There are 20 columns in total (8 columns per side, 4 columns from mid to back of the building, where the total width is more than 18 feet).

    Foundation depth for each column is 6ft deep, 3ft x 3ft 12mm mesh for footing. Each column has 4 iron rods which are 12mm.

    Soil is very solid and we had pour water in order to wet and loose it before digging.

    All the columns are connected with beams, we have used 12mm rod for all beams. Only for 2 beams which are 16ft length, we have used 16mm in bottom, 12mm on top. 10mm rods are used for floor concrete for each story.

    The column distance varies from 18ft to 8ft.

    • Hello Faisal,

      By my rough estimate, your footings are inadequate to handle load of a G+2 building. If the underlying soil is hard rocky soil, we can assume a maximum safe bearing capacity of 35 tons per square meter. But a footing of size 3′ X 3′ has a maximum capacity of 28 tons as its area is 0.80 square meter. A general rough estimate puts load on a column and its footing at 15 tons to 20 tons per floor for reasonable spans like in your building. This can vary greatly and has to be calculated by a competent engineer. This means your footings are at capacity and the G+1 floors have already consumed available carrying capacity of a 3′ X 3′ footing.

      I would recommend against building another floor.

  273. Hello.

    How can i design slab, beam, column of second floor of old school building.
    School building has G+1 with parapet.

    Existing column size 9″*12″ and steel 8-20T

    And how can i fix column and beam on slab of first floor instead of parapet.

    • If you looking at extending the building, that is building the second floor then you will have extend the existing first floor columns. You will of course have to lose the parapet.

    • Hi Shashank,

      It is difficult to answer your question based on the information you have provided.
      It depends what the floor plan is like and most importantly what the ground is like where this structure would sit. What kind of foundation have you designed for it?

  280. Dear madam/sir

    I strat next month my house work.house area is 656.2 Sqft.kindly request to yoy please send footing and column sizes and reinforcement details and distance of every columns and roof slab thickness and reinforcement details. house size is 17 feet *38.6feet

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