when paint peels on a plastered wall the thing to know is that something is causing the surface to peel and you will need to determine the cause there are a few common causes for peeling such as bad preparation when the wall was previously painted or moisture which can cause fungal growth under the topcoat whatever the cause it's important to fix the problem and get down to a sound surface before repainting begin the repair by scraping away the peeling paint and have a look at the surface in cases where the plaster is sound but may not have been primed or under coated correctly give the area a good scrape to remove the flaking paint feather the edges of the remaining paint with sandpaper is possible so that the repair won't be noticeable and brush away all the remaining dust from the wall you will now have a sound surface to work on if there's any plaster damage repair that before applying the finishing coats now you have a sound surface to work on and the painting can be done begin the finishing process with a coat of plaster primer spot prime the areas of wall that you've been working on it's not necessary to prime the entire wall when the primer is dry apply the desired topcoat as an undercoat for the repaired area once the undercoat is dry the wall can be finished with two top coats of acrylic emulsion check out our movie on painting a house exterior for a look at painting outside walls your paint dealer will be able to match up the existing color of your walls if you take a sample into the paint store don't try to work with those little color swatches you'll pull your hair out doing that scrape off a flake of paint about three centimeters in size and take it in for sampling that should do the trick