Causes of Foundation Damage | Moisture

Foundation Damage caused due to Moisture absorption

In my earlier articles, we discussed some of the important causes of foundation damage.

• Foundation damage caused due to erosion
• Foundation damage caused due to Fungus rot and Insects

Getting a clarity on the subject helps you prevent your structure from further damage or any damage that might happen in future. We have also discussed “how analysis of foundation damage is to be carried out”.

In this article, we will discuss in detail the foundation damage occurring due to Moisture. This element is also responsible for foundation damage and if ignored or left unnoticed can cause severe damage resulting in structural failure.

Types of foundation damage can be classified as follows:

Erosion

1. Natural rock
2. Brick

Rot

Insects

Moisture damage

1. Frost wedging
2. Salt bloom

Settlement in the ground

1. Groundwater lowering
2. Limited bearing capacity of the ground (land)
3. Excavations performed below the foundations and poor quality of backfill
4. Increased load on the ground leading to failure
5. Damage to the neighbouring houses
6. Increased load
7. Damage (by removing) to the neighbouring houses
8. Horizontal movement occurring in the ground

Frost heave/adfreezing

Alum shale

Let us move on with the discussion on damage caused by moisture to the foundations.

Moisture damage

In older buildings, the walls were covered with clay and lime as mortar. These building materials are moisture absorbent. The walls do not undergo severe damage as long as the lime and clay walls are not treated with any other building material.

For example:

In an old building where the plastering has been done using lime and clay suffers from some chipping and damage. This calls for locals repairs which are to be done to maintain the aesthetics of the structure.

Since, cement mortar is a modern material and is available in abundance, the repairs are done with Cement mortar.

Before initiating such tasks, it is to be remembered that the coefficient of expansion of different materials is different. When cement mortar is used as a repair material over lime mortar, due to different moisture absorption properties and coefficient of expansion, the combination does not work very well.

As compared to clay and lime, the cement mortar is relatively tight and disturbs the moisture balance in the wall. This results in creation of spaces in between the cement mortar and the wall which does not let the air escape which results in the further absorption of moisture into the walls. In this way, if precautions are not taken, old buildings or Old Heritage Buildings could suffer from severe damage.

Moisture damage caused to the foundations can be classified into two types:

Foundation damage caused due to Frost wedging

Water penetration into the building materials is extremely disastrous for any structure. In this case, the water penetrates into the walls. When the temperature of the surroundings drop, the water in the cracks of the walls freezes. Due to the freezing of water and its conversion into ice, the mortar material breaks into pieces. The mortar losses its binding ability and crumbles into small pieces.

Foundation damage caused due to Salt bloom

When the water penetrates into the foundation walls, the probability of it carrying soluble salts with it increases.

For example:

When the water penetrates into the walls, the soluble salts present in the building materials i.e. mortar or stone, get dissolved into the water and move along with the water.

As soon as water finds a exit through the wall, it deposits all the salts on the outer surface of the foundation and evaporates. This is termed as “salt bloom”. This could result into damaging the surface of the foundation and sometimes may also result into crystallization of the inner rock or the exterior surface of the rock which would result into flaking of the mortar or rock material.

Also check out:

Repair and Maintenance of Old buildings guide