How to fix foundational cracks and painting?

Bill1990

Hi Bunnings workshop community,

Nearly 10 years ago in a newly built house, some cracks showed up and was told to us that they were "foundational cracks". I've attached some photos. The discoloration around the cracks was from the builders trying to paint over with the wrong shade of paint.

I would like to tackle this problem, but have a few questions to ask:
1. Can I just use a generic wall kit for cracks like these (doorframe, wall, corner) e.g. https://www.bunnings.com.au/selleys-spakfilla-wall-repair-kit_p0436967
2. What is the recommended safety precautions around sanding the paint/wall? I do not own a shopvac, so any recommendations of a shopvac with a hepa filter that would help here would be appreciated.
3. For painting over these cracks, do I need to perform any priming/multiple coats?

Somewhat relatedly, another part of the house has a ceiling where the roof leak was fixed years ago, but the leak spot never touched up. I was wondering if I could just paint over this? Picture attached below.

Thanks in advance!

MitchellMc

Welcome to the Bunnings Workshop community @Bill1990. It's terrific to have you join us, and many thanks for your question about fixing cracks and painting.
 

Before jumping into repairs, I’d first ask: were the foundational issues ever properly addressed or corrected when the cracks first appeared? There’s a big difference between superficial hairline cracks that come from general settling and movement, and more serious cracks caused by foundation movement.

Foundational movement refers to shifts in the structure beneath your house — often due to soil movement, moisture imbalance, or poor compaction during the build. These types of cracks can compromise the structure if not stabilised, and just filling and painting over them won't fix the root problem. If you haven’t already, it’s worth getting a qualified professional to assess the area and confirm whether the issue was properly corrected and the home is structurally sound.

Now, if the foundational concerns were resolved during or shortly after the build, and the cracks haven’t widened or spread over the last 10 years, then you can treat them as cosmetic and go ahead with repairs.

The kit you mentioned (the Selleys Spakfilla Wall Repair Kit) is more suited for patching small holes in plasterboard, like those left behind by picture hooks or accidental dings. For these cracks, especially around corners and doorframes, you’ll just need a flexible gap filler or interior Spakfilla, depending on the crack width. Once filled, sand it back flush with the wall. Around the door frame you should likely use a caulked flexible gap filler product rather than the Spakfilla.

In terms of painting, yes — prime the patched area first (two coats if needed), and then follow with your colour-matched topcoat. A good quality wall primer will help ensure even coverage.

As for sanding safely, it’s a good idea to wear a dust mask or respirator (look for P2-rated masks), and if you're considering a shop vacuum, Bunnings has a few models with HEPA filters but those are typically seen in trade quality vacs. You might consider the Ryobi shop vac with an added HEPA filter. 

For the water stain on the ceiling, once you’re sure the leak has been fixed and it’s completely dry, use a stain-blocking primer (like Zinsser BIN) before painting over it. Otherwise, the stain can bleed through even fresh paint.

Please let me know if you have any questions.

Mitchell