If your wall is damaged, or if you’ve been aggressive with removing a tile, the wall plaster may be crumbling and will not hold the weight of any finishes
You’ll need to repair your wall before proceeding with any architectural finishes. Tiles, paint, and plaster stick better to a clean and uniformly flat surface – and you would be using more mortar than you should to make a tile stick to an uneven wall.
1. Use a hammer and chisel, or a metal hand-held scraper, to remove any loose bits of cement off your wall.
2. Wipe the wall down with a damp cloth to ensure that the surface is clean.
3. Mix ordinary Portland cement with fine river sand at a ratio of 1:4 (one part cement combined with four equal parts of sand) and add enough water so that you end up with something resembling cake batter. If you're working in an area that will get wet often, it wouldn't hurt to provide the wall with further protection by adding a plasticising additive to the mix.
4. Trowel the cement mixture to the wall in thin coats, using the flat profile of the trowel to make the surface smooth while it is still wet and workable.
5. Let the cement dry fully for two to three days and lightly sand it down before proceeding to install architectural finishes such as paint, plaster, or tiles. If you lay anything else on too soon, the moisture left in there will be trapped and your finishes might pop out.
Now that you've repaired your wall, you might be wondering what to do with it. Go for the post-industrial look by laying a coat of concrete sealant over it; or take the artistic route with paint, plaster, tiles, or even epoxy-marbled panels.
This article is intended to convey general information only. It does not constitute advice for your specific needs. This article cannot disclose all of the risks and other factors necessary to evaluate a particular situation.
Any interested party should study each situation carefully. You should seek and obtain independent professional advice for your specific needs and situation.