Demolition of old suspended ceiling
If the original foundation is not handled well, it will still be deformed. Therefore, resolutely dismantle the old ceiling and repaint, scrub, paint or paste wallpaper after shaving. Most paints are water-based and environmentally friendly, but remember to buy good putty powder. Now the weather is just right, it will be done in 3-5 days!
Insulation board/cement is missing.
Remove the insulation board or cement from the wall, put a layer of gypsum board outside and brush latex paint. However, the workload is heavy and difficult.
Moisture is the culprit.
Wall cracks are mostly caused by water volatilization, and may continue to crack even if repaired. Small area painting will have color difference. Want to reduce cracking? Stick non-woven fabric on the wall first to reduce cracking by more than 80%! The cost will increase, but quality glue is the key!