Whether you are planning to complete an elaborate mural or just want to get your walls back to crisp, clean white, you won't be happy with your painted wall unless you first repair any surface defects. A number of factors might cause your walls to seem uneven, including stains and discolourations, faux-effect paint treatments, residual wallpaper paste, peeling paint, cracks and shallow holes. Prepare an uneven wall before painting so your completed project looks professional and lasts for years.
Lay out your dust sheets across the floors and over furniture. Apply tape around mouldings that you don't plan to paint, and remove any switch plates or outlet covers. Dust the walls to remove cobwebs and dust accumulations, and then wipe away dirt and grime with a soapy, damp sponge.
Scrape away old, flaking or peeling paint with a scraping tool that has a wide, flat edge. Trim off torn drywall paper with a utility knife.
Apply joint compound into cracks and small holes. Purchase a water-resistant joint compound if you're planning to paint a wall located in a room that is frequently moist, such as a kitchen or a bathroom. Use your wide blade scraping tool to cover larger recessed areas, and use a putty knife for the smaller holes and cracks. Apply more than the damaged area visibly needs, since the compound will shrink as it dries.
Sand smooth any excess joint compound after the surfaces are completely dry. Also use your sanding block or palm sander to even out areas where you removed peeling paint and sand down wallpaper paste remnants.
Cover stained areas on your walls with a specially formulated primer/sealer for killing stains. Once all other preparations have dried, cover the entire surface with a coat or two of paint primer. This will create a fresh, even surface for paint, and hides the appearance of multiple colours from decorative paint treatments or damage. Primer also creates an evenly textured surface, which is necessary if you've used joint compound on your walls since the dried compound absorbs paint differently than normal painted surfaces.