How to repair crack in plastered brick wall?

Question

I'm repairing a number of plaster wall cracks in a 50 year old home that is constructed of double brick using strip footings in clay soil (clay  moves with seasons) not a concrete raft slab. The cracks open and close with the seasons (movement in the footings due to clay expanding and contacting with moisture), cracks open 2-3mm and will close completely over the seasons. What is the recommended repair method and produces.

Cheers Peter

Dave-1 · Answer

Good Morning @Mawbs

Thats a fair amount of expansion, Is there a chance of some photos showing the cracks? I get movement in my walls with seasons as well tho id say the cracks look more like 1mm ish (They stand out a lot more then 1mm lol) I havnt had to deal with large cracks like you describe that open and close with the seasons. I would go the route @EricL has suggested.

Dave

EricL · Answer

Hello @Mawbs

Welcome to the Bunnings Workshop community. It's wonderful to have you join us and thanks for sharing your question about repairing the crack in your plastered brick wall.

In the interest of health and safety, I suggest having your wall tested for asbestos before you start or carry out any repairs. If the test is positive, you'll need the services of an asbestos removal specialist. But if the test is negative, you can continue with your repairs.

For a 50-year-old double-brick house on strip footings in reactive clay soil, the key issue is that the cracks are active movement cracks, not simply cosmetic cracks. Because the cracks seasonally open to 2 to 3 mm and then close completely, any rigid repair (standard plaster patching, hard-setting filler, joint compound alone, etc.) will almost certainly crack again.

I propose using

https://www.bunnings.com.au/sika-310ml-white-sikaseal-acrylic-100-gap-filler_p1670226

or

https://www.bunnings.com.au/selleys-475g-no-more-gaps-interior-multipurpose-gap-filler_p1230010

. Both have been designed to cope with movement and can be painted over.

I recommend the following steps for persistent structural movement:

* Rout out the crack to approximately 5 mm wide
* Fill entirely with high-quality paintable acrylic sealant
* Tool smooth the surface
* You may sand the surface lightly to get a flat finish
* Dust and clean the surface before painting directly over the sealer.

Please make sure that the sealer has totally cured before sanding or painting the surface. This may leave a faint visible line but often lasts much longer than plaster-based repairs.

Let me call on our experienced members @Dave-1, @Nailbag, @TedBear, @JoeAzza, @Remarka6le and @DIY4Knuckleheds for their recommendations.

Please make sure to wear personal protection such as gloves goggles and a mask.

If you have any other questions we can help with, please let us know.

Eric