Ask a building inspector – Why is my wall cracking?
My boundary wall has these huge cracks that run from the top to the bottom and I am scared it is going to fall over. What do I do? Please help. – Jenny
Dear Jenny, do your boundary walls look like the below photos?
All the cracks in the photos have formed because expansion joints were not created at all or not created correctly on the boundary walls. The artisans who built these boundary walls were not skilled and there was no supervision. The most they did in some cases was to draw a line in the plaster.
Expansion joints, also referred to as control joints, allow segments to move independently of each other while retaining the integrity of the structure.
When a crack is visible in a joint it is often mistaken as a structural crack, but it is only the filling material which has cracked and not the wall or bricks.
A boundary wall cannot be constructed as one long wall because it will crack in certain places, due to the different soil and moisture conditions below and expansion and contraction of the material. The wall is constructed in different independent panels with gaps in between to allow them to move, so that no cracks will occur.
The joints should be filled with polyurethane foam, and a waterproof silicone on top to prevent water ingress, and not a hard filler product or plaster.
Another place where gaps occur is between the cornice and the ceiling and the wall. This is due to the shrinkage of the cornice and the ceiling board over a period of time. The moulded polystyrene cornices are glued to the wall and the ceiling, and the shrinkage can cause the de-bonding. Ask the painter to fill these gaps with an acrylic silicone before the painting is done. The cornice is to be nailed only to the ceiling and not to the wall, to accommodate future movement. Remember that the ceiling is fixed to the roof trusses which are moved by the wind.
The above crack is the result of a different cause. The electrical conduit pipe was not chased in deep enough and the contractor did not use chicken mess to cover the pipe before plastering. There are two ways to solve this: Create an expansion joint correctly or chase the pipe in deep enough and cover with chicken mesh and then plaster and paint again.
In my book The Proud Home Owner I give a great deal of detail on how to create expansion joints correctly.
If you are unsure about the cracks and how to repair them, let Gauteng Home Inspections do a crack inspection for you.
Got a building-related question? Email firstname.lastname@example.org and we’ll be sure to assist you
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Who is Albert van Wyk?
Albert van Wyk of Gauteng Home Inspections and author of The Proud Home Owner has been in the building industry for more than 38 years, having built many luxurious houses on difficult stands to the satisfaction of very meticulous clients as well as office blocks, factories, cluster developments and townhouse developments. Many of the homes were featured in SA Home Owner and on the TV program, Top Billing.
Albert has extensive knowledge of the National Building Regulations and the NHBRC requirements, and is one of only 40 ITC-certified Roof Inspectors in the country.