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Here’s how you know if your home’s foundation is compromised

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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.

Structural cracks

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.

This is a structural crack which was caused when a foundation sagged. The gap of the crack is also bigger at the top than on the bottom.

This is a structural crack which was caused when a foundation sagged. The gap of the crack is also bigger at the top than on the bottom.

 

The corner on the right has sagged and caused the crack. The gap in the wall is bigger on the top than on the bottom.

The corner on the right has sagged and caused the crack.
The gap in the wall is bigger on the top than on the bottom.

 

Either one of these two structural cracks can happen when the foundation sagged in the corner. Could be because of collapsing soil, under designed footing or weak concrete.

Either one of these two structural cracks can happen when the foundation sagged in the corner. Could be because of collapsing soil, under designed footing or weak concrete.

 

This structural crack was caused by heaving clay. The gap of the crack is usually bigger on the bottom than at the top.

This structural crack was caused by heaving clay. The gap of the crack is usually bigger on the bottom than at the top.

 

crack illustrate

This is to illustrate how different cracks can develop when the foundation has sagged in different areas

7 reasons why foundations saghome foundation

  1. Soft or sandy soil that cannot support the weight of the building.
  2. 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.
  3. A major change in the moisture content of the soil around and below the house.
  4. 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.

  5. The footings are not correctly designed for the type of soil; it is “under designed”.
  6. Poor workmanship; the contractor did not follow the instructions of the engineer.
  7. 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


For more, and to order your copy of The Proud Home Owner, click here, or visit Gauteng Home Inspections if you’re building, buying or doing maintenance

david.steynberg@gmail.com

David A Steynberg, managing editor and director of HomeTimes, has more than 10 years of experience as both a journalist and editor, having headed up Business Day’s HomeFront supplement, SAPOA’s range of four printed titles, digimags Asset in Africa and the South African Planning Institute’s official title, Planning Africa, as well as B2B titles, Building Africa and Water, Sewage & Effluent magazines. He began his career at Farmer’s Weekly magazine before moving on to People Magazine where he was awarded two Excellence Awards for Best Real Life feature as well as Writer of the Year runner-up. He is also a past fellow of the International Women’s Media Foundation.

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