When your plaster wall's are uneven, it is hard to not notice. The condition may be due to a variety of factors ,including a flawed application process, thin plaster covering drywall defects, or shifting of underlying drywall or lathe due to settling of the home. Cover the uneven plaster to disguise the interior problem. Work with a professional or attempt the project yourself.
Plain finishes used to cover your uneven drywall often include joint compound, also known as drywall mud. Traditionally, the product evens out drywall joints and tape. It is an inexpensive material that comes in dry form or premixed. Occasionally, clean sand is added to the plaster for additional grit. Always use a drill mixer to stir the joint compound before use.
Use a drywall trowel, putty knife or blade to apply the joint compound to the wall. Smooth on all uneven surfaces or skim the entire wall. You will only be adding a small, thin layer of the plaster. Applying thick layers often causes the material to crack. If the wall continues to be uneven, add a second or third layer of plaster. Allow each layer to fully dry and sand with medium sand paper. Always remove drywall dust by wiping with a wet towel.
Once the walls are smoothed out, you should apply a finish coat of acrylic paint. Flat paint is best to paint walls, especially when attempting to hide uneven areas. Imperfections such are more noticeable with glossy paints. Avoid eggshell, satin or high gloss paints. Apply two coats or more of paint. Joint compound is a dry, chalky material that will absorb the first coat of paint.
Once your project is complete, you may still notice slightly uneven wall areas. These areas may not smooth out, no matter what plain finish you apply. Heavier textures may hide the areas better than a plain finish. The textures include knockdown or skip trowel faux finish techniques. If you are unsure what the best finish is for your walls, consult with a drywall professional. He will provide samples of finishes and be able to physically view the problem areas.