To obtain a good result when repainting your wall, it is necessary to first apply an undercoat. However, for it to adhere correctly, sanding is essential. The sanding required varies depending on the condition of the wall, and it must be carried out methodically to avoid surface defects.
Should you sand your wall before undercoating?
Before applying the undercoat of paint when you want to repaint a wall, it is necessary to sand it. In fact, the undercoat will only adhere well if the surface is clean and well degreased. If the wall was already painted, light sanding followed by dusting will be sufficient. If it is not, more thorough sanding may be necessary. In all cases, the objective is to have a uniform surface that is as flat and clean as possible.
How to sand your wall correctly before undercoating?
It is important to sand methodically. Indeed, you must make sure not to go over the same places several times, which would result in differences in levels and excess paint depending on the areas. Use sandpaper or a sanding block. On a wall already painted with water-based paint, use fine-grained sandpaper (No. 0 steel wool); for oil-based paint, take a medium grain, between 100 and 150. Note that if an old paint is cracked, you will need to take the time to remove all the scales before sanding carefully.
Once sanding is complete, remove the dust from the sanding using a damp cloth, and wait for complete drying before applying the undercoat.
It may also be necessary to gently sand the wall after undercoating if some small defects persist. Here again, it is by having a smooth and uniform surface that the paint will stick best to the undercoat.