Prep Tips for Painting Walls

Preparing walls for painting is the most difficult part of the painting process. If you don’t put in the time to scrape, patch, sand, and prime the walls, your finished project will show it.  To get beautiful, glass-smooth walls and baseboards, follow these simple preparation tips.

How to Prep Walls for Painting

  • Dust and vacuum all surfaces. For good measure, wash the walls with soap and water. This is especially important in kitchens and bathrooms. If you see evidence of mold, which appears as gray-green speckles, use a solution of up to a quart of bleach to three quarts of ammonia-free detergent. (Never mix bleach with ammonia.) Dab the solution on the area, and allow it to sit for about 10 minutes before rinsing thoroughly.
  • Cover floors and furniture with newspaper or drop cloths.
  • Smooth the walls. Direct a flashlight across the walls to double-check for problems. For cracks or flaking areas, use a paint scraper until you reach a solid coat of paint beneath. If you find torn drywall, trim the torn piece with a knife and apply joint compound over the damaged area. For large, bare patches use a wide blade to apply several thin coats of joint compound (instead of a thick coat). Once you have applied the compound and let it dry, smooth it with a palm sander or sanding block.
  • Fix surface stains with a detergent-water solution or solvent/spot remover. If the wall is discolored, seal the area with a stain-removing primer such as white shellac, which also effectively covers knots in paneling or trim and prevents resins from bleeding through.
  • Prime any repaired areas according to the paint manufacturer’s instructions. This step ensures the paint will adhere well, preventing future peeling. Check recommendations for priming unpainted wood, which may need a different type of primer. If you are repainting walls or ceilings, you may not need to prime them first—unless, for example, you are changing from a dark color to a light color, or you are trying to cover stained areas. You will need to apply primer to any joint compound repairs to prevent an uneven appearance. Besides, a layer of tinted primer is less expensive than two coats of paint.
  • To prepare the trim, you will also need to lightly sand imperfections. You may need to take old paint down to the raw wood by stripping, sanding, heating, and/or scraping the affected section. If the paint was applied before the late 1970s, you should test for lead before removing. You will need a heat gun to scrape off old baseboard paint. Keep the nozzle of the gun moving across the surface while you scrape it with a stiff scraper. A razor-edge scraper can be used to clear grooves in molding.

Things you Need

  • Vacuum cleaner
  • Soap and water
  • Bleach
  • Ammonia-free detergent
  • Drop cloths or newspaper
  • Flashlight
  • Paint scraper
  • Joint compound
  • Knife and wide blade
  • Power palm sander or sanding block
  • Solvent or spot remover
  • White shellac or stain-removing primer
  • Primer or tinted primer
  • Heat gun (if prepping baseboards)


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