How to Paint Over Dirty Walls
Painting over a dirty wall is only going to lead to problems. You should take steps to make sure that a dirty wall is as clean as you can get it before you apply any paint. Any dirt or grime that is left on the wall will interfere with the ability of the paint to stick to the wall.
Use a vacuum cleaner or a dust mop to clean off the surface of the wall. Dampen a paper towel with vinegar and rub it over the wall. The dirt and grime that you can't see on the wall will show up on the paper towel and give you an indication of how much you need to clean the wall to prepare it for painting.
Use two separate 5-gallon buckets for wet cleaning. Use two separate sponge head mops. Label one mop for washing and the other for rinsing to distinguish them. Keep the mops separate so that you don't confuse them during cleaning.
Fill the cleaning bucket with 3 gallons of warm water. Add 3/4 cup of trisodium phosphate (or 1/4 cup of trisodium phosphate for every gallon of water). Make sure to mix the components completely.
Fill the rinsing bucket with 3 gallons of warm water. Add 3 cups of distilled white vinegar (or 1 cup of distilled white vinegar for every gallon of water). Mix this solution well.
Use a sponge mop with a scrubbing head. Work from the bottom up and wash the walls in 8-foot widths. Work your way around the room. When come back to your starting point, turn the mop head around. Start scrubbing the wall with the nylon scrubbing head of the mop.
Use the rinsing solution after cleaning the first 8-foot section. Immediately rinse with the rinsing solution to remove dirt as well as the cleaning solution from the surface of the wall.
Make sure to change the rinsing solution often. The vinegar inside the rinsing solution is an astringent that neutralizes the phosphors, which could prevent appropriate bonding of the paint to the surface.
Let the wall dry completely before painting it.
Things You Will Need
- Vacuum cleaner or dust mop
- Paper towel
- Two 5-gallon buckets
- Trisodium phosphate
- Distilled white vinegar
- Two sponge mops with scrubbing heads
- Household cleaner (optional)
- Hydrogen peroxide (optional)
- Gloves (optional)
- Goggles (optional)
- For walls that have mildew on them, mix 1 cup of household cleaner and 2 cups of hydrogen peroxide in 1 gallon of warm water. Wearing gloves and goggles, apply this solution with a sponge or mop to areas of the wall covered in mildew. Let it stand for a few minutes and then rinse it with a solution of 1 cup vinegar in 1 gallon of water.