How to Clean Walls Before Painting

Skipping wall cleaning before painting is a common shortcut, and it's also a common cause of adhesion problems that show up later — dust, grease, and residue on a wall's surface all interfere with how well paint bonds, regardless of how good the paint itself is.

1. Light dust and general dirt: a dry or lightly damp wipe

A microfiber cloth, or a soft-bristle broom/vacuum attachment for the whole wall,
followed by a damp (not wet) cloth wipe

For a wall with just ordinary accumulated dust, this simple pass is usually sufficient — dust alone is a mechanical barrier between wall and paint rather than a chemical one, so it doesn't need a cleaning solution, just physical removal.

2. Grease and cooking residue: TSP or a TSP substitute

Trisodium phosphate (TSP) or a phosphate-free TSP substitute, diluted per label
directions, applied with a sponge, then rinsed with clean water

This matters most in kitchens, where airborne cooking grease settles on walls (even walls not immediately adjacent to the stove) over time as an invisible film — this is genuinely one of the most common causes of poor paint adhesion in a kitchen specifically, and a plain water wipe doesn't cut through grease the way a degreasing cleaner does.

3. Smoke or nicotine residue

Walls with smoke exposure (tobacco or otherwise) need a degreasing cleaner similar to the kitchen approach above, since smoke residue is itself an oily film — but heavier smoke staining also typically needs a dedicated stain-blocking primer afterward (the same category covered for water stains and knot bleed elsewhere), since smoke residue can bleed through paint even after a thorough cleaning.

4. Mildew: a bleach solution, then a mildew-resistant approach going forward

A diluted bleach solution (roughly 1 part bleach to 3 parts water), applied,
allowed to sit briefly, then rinsed thoroughly and dried completely

Visible mildew (distinct from mold, though related — see why painting over mold or mildew without addressing it doesn't solve the underlying problem) needs to actually be killed and removed, not just wiped, before painting — and the room's moisture source, if there is one, is worth addressing the same way it would be for mold.

5. Rinse thoroughly regardless of which cleaner was used

Any cleaning solution left as residue on the wall — TSP, bleach, a general household cleaner — can itself interfere with paint adhesion if not rinsed off completely. A clean-water rinse pass after any cleaning solution, followed by letting the wall dry fully, is a step worth not skipping regardless of which cleaning method was used.

6. Let the wall dry completely before painting

Painting over a wall that's still damp from cleaning — even if it looks dry on the surface — can trap that moisture under the new paint film, leading to the same kind of adhesion and peeling problems associated with painting over any other damp surface. Allowing a full drying period (often overnight, depending on humidity and ventilation) before starting to paint is worth the wait.