How to prepare uneven walls for painting?

mooglett

After my kitchen renovation the last part is to paint the areas that are mismatched from removing old water tank/new wires etc..

Im not sure the render type, however it is bubbly in texture but flat in new patches of concrete that covers new wiring areas.

How should i go about prepping and painting if planning on matching the white?

With the new concrete patches, does it needs some sanding to get rid of uneven parts first? Not sure i can match the “bubble” effect if apply new concrete.

Then should i paint the areas that need it? Colour matching can be done if i bring in a sample of the render?

Or would it be best to paint the whole room? My whole apartment is the same white.

Building is 1935 for context.

Thank you in advance for advice!

MitchellMc

Welcome to the Bunnings Workshop community @mooglett. It's wonderful to have you join us and many thanks for your question on painting walls.

You’re right to focus on prep first, because the current issue isn’t really the paint colour, it’s the condition of the surface. From what you’ve shown, the walls and ceiling have uneven areas where patches sit proud and other spots that dip, so the first step is to get everything back onto a consistent plane. That means knocking down any high spots with sanding, and then using a skim coat to fill low areas and smooth things out. The ceiling in particular needs to be as flat as possible, since light will highlight every imperfection. Sanding is definitely required, both to reduce uneven concrete patches and to feather edges so repairs blend into the existing wall. Remember your PPE including a face mask.

Just due to the age of the property, it's important to be aware that asbestos was commonly used on properties of that era. Any cement sheeting should be presumed to contain asbestos and not disturbed, unless verified otherwise.

Once the surface is level, you’ll need to decide whether to try matching the existing “bubbly” texture or go for a smooth finish. Matching the texture is possible but difficult without knowing how it was originally applied. It could have been done with a textured roller or stippling technique, so even with effort it may not look identical. Because of that, a lot of people in your situation choose to skim coat more broadly and create a consistent smooth finish instead, which tends to look cleaner and more modern.

After the surface is sorted, priming is essential, especially over new concrete or plaster, as those areas will otherwise absorb paint differently and show through. In terms of colour, while you can get a paint match from a sample, patched areas often still stand out due to differences in sheen and the age of the existing paint. For that reason, it’s best to paint at least the entire wall, and ideally the whole room if you want a uniform result, especially since your apartment is all the same white.

Please let me know if you have any questions.

Mitchell