Here’s how you know if your home’s foundation is compromised
There is no user manual for all aspects of homeownership, from moving, to taking occupation and to maintaining and understanding common and uncommon defects. Albert van Wyk has more than 38 years’ worth of building experience and has put all he has learned into a concise, easy-to-use reference book entitled, The Proud Home Owner. He has granted HomeTimes exclusive access to republish portions of his book to help homeowners make better decisions around buying and selling, as well as maintaining their properties.
As the name indicates, the structure has cracked and this is serious. It is usually due to foundation movement. Structural movement is serious when the safety-margins of strength, stability, or integrity have been significantly eroded, or the movement is progressively leading to failure.
Cracks can develop after a period of time, especially when the house is built on clay/expansive soils or soft sandy soil. The amount of water that gets in under the foundation of the house is directly related to the amount of movement which will take place.
The crack patterns in the walls will be an indication of what has happened below the foundations. The gap in a structural crack is usually larger at the one end.
It is possible to determine the cause of a crack by looking at the point where it started and the direction it has followed. It is also a fact that the crack started at the end with the large gap. With this in mind, fairly accurate assumptions can be made of the causes.
There are no fixed patterns or routes which cracks will follow; they follow the path of least resistance. If the strength of the mortar is greater than that of the bricks, the crack will extend through the bricks. If the strength of the mortar is less than the strength of the bricks, the crack will follow the mortar bed and the perpend joints. It is usually in a step form.
A big sudden collapse of the foundation could even shear the bricks.
When the middle of the surface bed has sagged, then the crack will start at the bottom and move upwards. The gap of the opening will be bigger at the bottom than at the top.
When the corners or the outside walls subside, the cracks will start at the weakest points in a wall, which are the corners of the window frames. These cracks will start at the top and move downwards, with the bigger gap at the top.
- Soft or sandy soil that cannot support the weight of the building.
- The foundation is constructed on different soil conditions e.g. when one part is on a rock formation and the rest on normal good soil or another part on soft sandy soil. The foundation must be designed to accommodate the worst scenario.
- A major change in the moisture content of the soil around and below the house.
The bearing capacity of the soil is not enough to support the building, or the bearing capacity of the soil has failed after the construction was completed. This is usually the case on sandy soft soils. In this case the building will settle after a while and then stabilise, because this soil is not as active under the house as the clay soil. Water will not be absorbed as in the clay soil but will drain away.
- The footings are not correctly designed for the type of soil; it is “under designed”.
- Poor workmanship; the contractor did not follow the instructions of the engineer.
- Another cause is poor maintenance. To allow water to pond around the house and to have flower beds next to the building can be classified as poor maintenance, because the water ingress can cause permanent damage to the foundation.
Albert says: “There are no fixed patterns or routes which cracks will follow”
Next time: These kinds of homes are more prone to cracks