Painting & Decorating

Filler in wall cracks keeps expanding after mist coats.

Anonymous user 28/02/2024 - 3.49 PM

Help, please!! I am decorating our hallway in a victorian terrace (built 1901). There are/were a large number of hairline cracks in the walls, some from ceiling to floor. I widened out the cracks with the trusty 5 in 1 tool, and filled the cracks with Diall Powder Filler (B and Q). Sanded the filler flush with the wall, and applied a mist coat. When dry, the filler in the cracks had expanded to be proud of the wall. So, sanded back level with the wall, applied another mist coat.................... the filler expanded to be proud of the wall. Sanded back again, applied another mist coat..............................filler expanded to be proud of the wall. I have done this 5 or 6 times now, and each time the filler in the crack has dried and expanded to be proud of the wall. How many times will I have to repeat this process before the filler remains level with the wall, and I can apply my first coat of emulsion? I have been home decorating for years, and have never experienced this before. Am I using the correct product for the job? I think so. Is the ratio of water to the powder during mixing of the filler somehow a factor in allowing the filler to keep expanding each time another mist coat is applied? When I filled the cracks I applied only enough filler to cover the cracks plus about 1/2" (12cm) each side of the crack. I am sanding all filler back to being level with the wall. Would I be better to gouge out all of the filler from each and every crack, and use decorators caulk instead? Any help with this would be greatly appreciated. Many thanks, Colourschemes and D.J. Decorators. I will try your suggestion when I prep the next room. I guess that I will just have to continue with the sanding and mist coating of the expanded filler until there's no more left to expand. I have noticed some areas of the cracks have stopped expanding since another round of sanding and mist coating. Oh well, lesson learned for next time. Once again, thank you for your input, gents; greatly appreciated.