How to clean walls before painting so the new paint sticks

Step by step: how to clean walls before painting so the new paint sticks

1. 1

   Clear the room and protect the floor

   Move furniture to the center, take down pictures and switch plates, and lay drop cloths or towels along the baseboards. Turn off power to any outlet you will wash closely around, and cover it with painter’s tape.

2. 2

   Dust the walls from the top down

   Vacuum the walls with a soft brush attachment, or sweep them with a microfiber duster, starting at the ceiling line and working down. Pay attention to the tops of baseboards, door frames and corners, where cobwebs and dust collect. Paint brushed over dust traps it in the finish.

3. 3

   Mix two buckets

   Fill one bucket with warm water and a few drops of dish soap, and the other with plain warm water for rinsing. On greasy kitchen walls or bathroom walls with soap film and hairspray, use a pre-paint cleaner mixed to the label’s ratio instead of dish soap.

4. 4

   Wash from the bottom up

   Wring the sponge until it is just damp and wash a section about 3 feet square, starting at the bottom of the wall and working up. Working upward keeps dirty drips from running down over dry wall and leaving streaks. Rinse the sponge in the soap bucket often.

5. 5

   Give dirty spots extra attention

   Around light switches, door handles, behind the stove and above the bed, grease and hand oils build up and stop paint from bonding. Wash these twice. Your sponge should come away clean before you move on.

6. 6

   Rinse with clean water

   Go back over each section with a second sponge dipped in the rinse bucket and wrung out. Soap or cleaner residue left on the wall can interfere with adhesion, so this step is not optional. Change the rinse water when it turns cloudy.

7. 7

   Let the wall dry completely

   Open windows or run a fan and let the walls dry for at least several hours, ideally overnight. Paint over damp drywall can bubble or peel. Run a hand over the wall: it should feel dry and slightly squeaky, not tacky.

8. 8

   Patch, sand and spot prime

   Fill holes and cracks after cleaning, let the filler dry, sand it smooth and wipe off the dust with a damp cloth. Spot prime patches and any stains that are still visible, such as water marks, crayon or smoke, with a stain-blocking primer.

Do you really need to wash walls before painting?

Yes for kitchens, bathrooms, hallways and kids’ rooms; often just dusting is enough for a clean bedroom or living room wall. Paint bonds to clean, dull, dry surfaces, and grease, soap film and dust are what cause peeling and fish-eye spots.

Benjamin Moore’s wall cleaning guide recommends dusting first, then trying plain warm water, then water with mild dish detergent, using one bucket for the washing solution and a second for rinse water, and washing from the bottom of the wall up to avoid streaks.

How to clean specific marks off a wall before painting

Most marks come off with the soap-and-water wash. The ones below need a little more, and some need primer rather than more scrubbing.

Wiping soot with a wet sponge first smears it into a gray haze, which is why the dry sponge comes first. For gummy tape and adhesive left behind by hooks and posters, use our guide on removing adhesive from a wall, then wash and rinse the spot before you prime.

How to prep glossy paint, trim and new drywall

Washing removes dirt, but it does not change the surface itself. Two kinds of wall need a different approach.

Glossy walls, trim and doors

Semi-gloss and gloss paint, common in kitchens, bathrooms and on trim and doors, is slick enough that new paint can struggle to grip it even when it is clean. After you wash, rinse and dry, scuff the surface lightly with a fine sanding sponge until the shine is dull all over, then wipe off the dust with a damp cloth and let it dry. A liquid deglosser is the no-sanding alternative; follow its label. In a home built before 1978, read the section on older homes below before you sand anything. Baseboards get the same treatment; our baseboard cleaning guide covers getting them clean first.

New drywall

New drywall is not dirty, it is dusty. Do not scrub it with a soapy, wet sponge: water softens joint compound and can rough up the paper face. Vacuum the walls with a soft brush attachment, then wipe them with a dry or barely damp microfiber cloth to pick up the fine sanding dust, and prime before you paint.

Ceilings

Most ceilings only need dusting with a microfiber pad on a pole. Wash ceilings only above a stove or in a bathroom with visible film. Textured ceilings are a separate job; see how to clean a popcorn ceiling.

How to tell the wall is clean and dry enough to paint

Run these quick checks on the dirtiest wall in the room before you open the paint.

• White cloth test. Wipe a clean, white, damp cloth across the wall at hand height and behind where furniture stood. It should come away clean.
• Water test. On a flat or eggshell wall, flick a few drops of water on the surface. If they bead up or crawl into droplets instead of wetting the wall, grease or cleaner residue is still there. Wash and rinse that area again.
• Hand test. Run a dry hand over the wall. It should feel dry and smooth, not slick, tacky or cool and damp. If your hand comes away with a chalky powder, the old paint is chalking; wash it off and ask at the paint store which primer suits a chalky surface.
• Check the slow spots. Corners, exterior walls, the area behind where a dresser stood and bathroom walls dry slowest, especially on cool or humid days.

What should you do about mold and stains before painting?

Clean mold off and fix the moisture before you paint; paint does not kill or hide it for long. The EPA says not to paint or caulk moldy surfaces, to clean up the mold and dry the surface first, and warns that paint applied over mold is likely to peel.

For small patches of mildew in a bathroom, follow our guide to removing mold from walls, then let the wall dry for a day before priming. Stains that survive washing, like water rings, marker, crayon and smoke, need a stain-blocking primer, or they bleed through even two coats of paint.

Is it safe to sand walls in an older home?

Not until you know whether the old paint contains lead. The EPA says homes built before 1978 are more likely to have lead-based paint and that dust and chips from it are one of the most common sources of lead exposure at home. If you must sand, the agency advises wetting the area first, sanding the minimum needed and cleaning up thoroughly.

Under the EPA’s Renovation, Repair and Painting rule, anyone paid to disturb painted surfaces in a pre-1978 home must be certified in lead-safe work practices. Washing walls with a damp sponge is fine, but for scraping and sanding in an older home, test the paint or hire a lead-safe certified painter.

Mistakes to avoid

• Skipping the rinse, so soap or cleaner film is left under the new paint.
• Washing from the top down and leaving dirty drip streaks.
• Painting the same day while the drywall is still damp.
• Painting over mildew instead of cleaning it and fixing the moisture.
• Using a soaking-wet sponge that swells drywall paper and seams.
• Dry-sanding old paint in a pre-1978 home without testing for lead.
• Scrubbing new drywall with a wet, soapy sponge, which softens the joint compound.
• Painting over glossy trim or semi-gloss walls without dulling the sheen first.
• Wiping soot with a wet sponge before using a dry soot sponge, which smears it.