In homes built before 1960, interior walls employed a combination of lath and plaster. In many older homes, these walls are still in existence and are in good enough condition to repaint. However, there are some considerations when preparing a plaster wall for paint. If you want to paint the plaster walls in your house, follow some general guidelines and you’ll have smooth walls that compliment your decor.
Remove old wallpaper before painting a plaster wall. While you can paint over existing paint, wallpaper, which was very popular in the latter part of the twentieth century, will buckle and bubble under a coat of paint.
Prepare the bare plaster wall for paint by inspecting it for gouges, cracks and loose plaster. Use the chisel to scrape crumbly plaster out of cracks before filling with premixed drywall mud.
Use the taper’s trowel to scoop up enough mud to fill the crack and smooth into the hole. Pull the edge of the trowel along the filled crack to smooth the mud level with the surface of the wall. If the crack is large, you may have to repeat the process until the it is filled and smooth.
Sand with a wall sander fitted with a sanding pad. These sanders fit on extension poles, making sanding along the top of the wall easier. Run your hand over the wall after sanding to make sure the wall is very smooth. If not, sand it again.
Vacuum dust from the room after sanding and wipe down the walls with a tack cloth to remove any dust still clinging to the plaster. Dust left on a wall will create a mottled effect in your paint.
Apply a stain-blocking primer to the plaster wall. Because plaster often has discoloured areas where rust spots bleed through from the lath area or stains exist, a blocking primer will seal these areas, preventing them from showing through the final paint coat.
Cut-in the paint along the edge of the wall where it meets the ceiling with an angled paintbrush. Cutting-in takes a light touch and a steady hand. Cut-in around the windows and doors as well.
Roll the wall, beginning in one corner and applying a smooth coat until you reach the opposite corner. Avoid pressing the roller into the wall to prevent paint runs.
Repeat the cutting-in process and the rolling process one more time for a professional finish.
Painting a light colour over a dark colour may require numerous coats to cover the old paint completely.