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What is the most flexible gap filler?

I am repairing cracking in the bathroom wall of a 50 year double brick apartment. It is just normal settling and minor cracking that one would expect for a building this age.

I have opened up the cracks to enable filling. What is the most flexible filler available for this purpose? The building will continue to move over time and I want to prevent as much cracking in the future as possible.

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MitchellMc

Hi @Edgar,

Where in the bathroom are these cracks occurring? Say, they were the corners in a shower recess, you'd use wet-area silicone. Or, if this is a crack that traverses across a wall out of the shower recess and follows the mortar joints, you could use Sikaflex 11FC. However, although highly flexible and paintable, the repair will likely be noticeable purely because it is a different surface than the surrounding area. Consideration should be given, if this is a crack that has developed over a long time, to filling the crack with a material more similar to the bricks/mortar. If these are rendered bricks or if the crack follows the mortar joints, you might wish to use Dunlop 4L Premix Render Joint And Patch instead. It's not flexible, but it might be worth it if you get a more invisible repair and you only have to touch up the crack again in 10 years' time.

Please let me know if you have any questions.

Mitchell

Edgar

Thank you. That's very helpful.

It also appears that part of the present paint job has laminated. I have peeled off the part that is easily removed. How should I prepare the surface so the surface is smooth and uniform? Thank you.

MitchellMc

Is it just the paint that has peeled off, or was it the paint and a thin layer of plaster skim coat, @Edgar? If it was just paint, then you can sand the stepped edge of the paint so you can't feel it with your fingers anymore. Prime with an oil-based primer-sealer for plaster surfaces, and when dry, apply two top coats of paint to the whole wall.

Alternatively, if it were also a thin coat of plaster, it would be best to reapply the topping compound over this area to bring it back to the same height. Spritz the wall with water so it is visibly damp before applying the skimcoat. Once dry, sand the area to a smooth surface. You can then apply the oil-based primer and topcoats.

Remember your PPE, including a face mask and safety glasses.

There's a risk of asbestos exposure from homes built or renovated before 1990. Before starting any work, determine if asbestos is present by having your home assessed and taking necessary precautions to protect yourself and others. Access resources from the Asbestos Safety and Eradication Agency for guidance on safe practices. Prioritise safety by educating yourself and seeking professional assistance when needed.

Please let me know if you have any questions.

Mitchell

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