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Here’s how to fix that crack in your wall

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.

How to repair cracksrepairing wall crack plaster

When should you worry about cracks? The crack must first be identified before a decision can be made.

You should get acquainted with the different filler produts because of the wide variety available. It is important that you select the most suitable product for your specific application.

Not all products are waterproof agents, and not all products can be painted over. Some products have a better adhesive quality than others; some will shrink and could crack when it is dry.

Albert says: “It is not urgent to fix hairline cracks; it can be done when you repaint the house next”

Hairline and shrinkage cracks in plasterhairline-crack-resize

These cracks are not more than 2mm or 3mm deep and about a millimeter wide. Do not try to open them further as you will only emphasise the crack more. The secret is to use a product with a very fine texture which can get on the inside of the crack. Pressure must also be applied to force the filling into the gap, using your thumb and a putty knife. I recommend Pollyfilla Mendall 90 to fill these cracks. You can also use it to fill the gaps between the cornice and the wall or ceiling. It has good flexibility and adhesion qualities, and will not fall out.

Live cracks in brick wallsbig crack in wall resize

These are cracks which have not settled or where there is continuous movement between two elements.

Fill the bulk of the crack with a polyurethane base silicone up to about 10mm from the surface of the wall. Now use your skills and try to match the finished surface with Acrylic silicone before it is painted.

Albert says: “It is not possible to stop the movement, so rather accommodate it”

Structural cracks in brick wallscracked house resize

These cracks must only be repaired after all the causes have been rectified. Find a good filler which will reach a high strength when it is dry. Some fillers crack during the drying process and then it is mistakenly thought that the crack has reappeared. You need a good filler which will expand and not shrink while drying, like ordinary cement will do. Any epoxy filler is good enough.

For more severe cracking it is advisable to form an expansion joint. This would be cut into the wall, filled with a compressible material with a waterproof sealant to the outside. On some modern buildings these are formed at construction stage and then hidden behind a rainwater downpipe.

Next time: Diagnosing damp

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 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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