How to Clean Walls Before Painting

Before you start

Start by deciding what is actually on the wall. Living rooms and bedrooms usually carry dust and light grime, which detergent handles. Kitchens carry cooking grease, bathrooms carry soap and body oil, and hallways carry hand oils, all of which resist ordinary washing. Match the cleaner to the contaminant: a degreaser where grease is present, a general wash everywhere else. Wear gloves and eye protection when you use degreasers or TSP, and protect the floor with a drop cloth.

Tools and materials

• Two buckets: one for the wash solution, one for clean rinse water
• Sponges or soft cloths, plus a separate clean cloth for rinsing
• Mild dish detergent for general grime
• A degreaser or TSP substitute such as Krud Kutter or Dirtex for kitchens and baths
• Gloves and eye protection, and a drop cloth for the floor

Cleaning is one step of the broader prep sequence in our how to prepare walls guide.

Surface preparation

Cleaning is the first step of surface preparation, and it comes before sanding for a reason: sanding a dirty wall grinds the dirt into the surface instead of removing it. The three cleaners cover three needs. Mild detergent lifts dust and light grime. A degreaser like Krud Kutter cuts kitchen grease. A product like Dirtex handles heavy grime and nicotine, and both substitute for traditional TSP without its residue and rinsing burden. The surface preparation hub places this step in the full clean-repair-sand sequence.

Step-by-step method

1. Dry-dust first

   Knock loose dust off the wall with a dry cloth or vacuum brush so the wash water does not just smear it around.

2. Wash with the right cleaner

   Use mild detergent for general grime, and switch to a degreaser or TSP substitute like Krud Kutter or Dirtex where grease or heavy grime is present.

3. Work bottom to top

   Start low and work up so dirty water does not streak down a wall you have already cleaned.

4. Rinse thoroughly

   Wipe with clean water and a fresh cloth to remove the cleaner. Leftover residue repels paint just as grease does.

5. Dry completely

   Let the wall dry fully before sanding or painting. A damp surface bubbles the film and fails the same way a dirty one does.

Quality checks

Run a clean white cloth over a dried section. If it comes away dirty or greasy, wash again. Check that no suds or cleaner film remains by wiping with a damp cloth and looking for residue. In a kitchen, test the wall above the stove, which carries the heaviest grease, rather than trusting a clean patch near the door.

Common mistakes

• Washing with hot water and heavy detergent on flat paint, which can soften the film
• Skipping the rinse, so cleaner residue sits under the new paint
• Using a degreaser only in the kitchen while skipping the bathroom and hallway hand-oil zones
• Painting before the wall is fully dry

Cleanup

Empty the buckets, rinse the sponges and cloths, and let the drop cloth dry before folding it. If you used TSP or a degreaser, dispose of the wash water according to the label rather than pouring concentrated residue down a drain you care about. Keep a clean, dry cloth set aside for the dust-removal step after sanding.

Next project step

With the walls clean and dry, move to repair and sanding, then remove the sanding dust before priming or painting. Our dust removal guide covers that next step, and the sandpaper grit page gives the numbers for the scuff that follows.

FAQs

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