How to Clean Walls Before Painting: Grease, Dust and Marks
What to use and how to wash walls and ceilings before painting, covering sugar soap, kitchens, smoke and nicotine stains, rinsing and drying time.
Fresh paint will not stick reliably to dirty, greasy or dusty surfaces. Washing walls is a dull but valuable step. It can be the difference between a finish that lasts and one that peels, crawls or shows patchy marks within months.
Why cleaning matters
Walls collect dust, cooking grease, hand marks, smoke residue and general grime. These create a film that prevents paint from bonding properly. Some contaminants, such as grease and nicotine, can also bleed through new paint and stain it.
Check what you are cleaning
Different surfaces need different treatment:
- Previously painted emulsion in good condition: can usually be washed.
- Bare or new plaster: do not soak. Dust and lightly wipe only.
- Wallpaper: not suitable for wet washing unless it is a washable type, and you are not removing it.
- Distempered or old chalky walls: may break down when wet. Test first.
What you will need
- Two buckets, one for cleaning solution and one for rinse water
- Sponge or soft cloth
- Mild detergent or a decorator's cleaning solution such as sugar soap, following label instructions
- Gloves and eye protection
- Step ladder, if reaching ceilings
- Old towels to catch drips
Step by step
- Dust first. Use a soft brush or vacuum to remove cobwebs and dust, working from the top of the room down, including ceilings, picture rails and tops of door frames.
- Protect the floor and electrics. Lay sheets and avoid soaking sockets and switches.
- Wash in sections. Start at the bottom and work upwards, so dirty runs do not leave streaks on clean areas. Use a damp, not dripping, sponge.
- Rinse. Many cleaners need rinsing with clean water to remove residue. Change the water often.
- Pay attention to hot spots. These include kitchen walls near the hob, around switches, door frames and the area above radiators.
- Allow to dry. Wait until completely dry, usually several hours, longer in cool or humid rooms.
Special situations
Kitchens
Grease needs a proper degreasing step. Wash twice if necessary, then rinse. Skipping this can cause paint to crawl or bead on application.
Smoke and nicotine staining
Nicotine can bleed through standard paint. After cleaning, a stain-blocking primer is typically needed.
Mould
Treat with an appropriate mould cleaner, and address the cause. See damp and mould before painting.
Glossy surfaces
Washing helps, but glossy walls and woodwork also need keying with sandpaper. See preparing woodwork for painting.
Mistakes to avoid
- Using too much water on plasterboard or new plaster
- Mixing cleaning products, which can be dangerous
- Not rinsing, leaving residue that affects adhesion
- Painting when the wall is still damp
- Ignoring ceilings, which collect more dust and cooking residue than you might expect
After cleaning
Once the walls are dry, fill and sand as needed. See filling and sanding walls. Then spot prime repairs and stains before applying the main coats.
If you hire a decorator, cleaning and degreasing are often part of the preparation, but confirm it is included. A Compito request can specify "kitchen, greasy walls" so providers can allow for it.
A worked example: a hallway that looks clean but is not
A hallway wall near the front door appears tidy, yet a damp cloth comes away grey. This is typical: hands, coats and pet fur leave an oily film that paint cannot grip. The sequence is to dust from the top, wash in sections from the bottom upwards with warm water and a mild detergent or a suitable cleaner, rinse with clean water, and leave to dry fully. The area next to the light switch and at hand height often needs two rounds. Only then fill, sand and paint.
Picking the right cleaner
| Situation | Sensible choice |
|---|---|
| Normal, lightly marked walls | Warm water with a little washing-up liquid |
| Greasy kitchen walls | A degreaser designed for painted surfaces |
| Nicotine or smoke | Specialist cleaner and a stain-blocking primer |
| Mould spotting | Mould treatment, then a damp-free wall |
| Chalky old paint | Dry brush and dust only, then a sealer |
Always test in a hidden corner. Strong chemicals can dull paint or lift weak finishes.
Common mistakes
- Mixing cleaning products. Some combinations release harmful fumes. Use one product at a time and follow the label.
- Soaking the wall. Excess water can run into sockets or soak plaster.
- Skipping the rinse. Residue stops paint from bonding.
- Painting damp walls. Allow longer in cool or humid weather.
- Forgetting ceilings and top corners. Dust and cobwebs sit there.
Safety around electrics
Avoid wetting sockets and switches. Wipe around them with a barely damp cloth and never spray liquid into them. If you are unsure about electrical safety in a room, ask a registered electrician rather than guessing.
Special situations
Rented homes. Wash only what you will repaint, and check the tenancy terms.
Children's rooms. Rinse thoroughly and ventilate, and consider low-odour paint afterwards. See low-VOC paint for children's rooms and nurseries.
Homes with allergy sufferers. Use damp cloths rather than dry dusting to avoid raising particles.
Test for readiness
Rub a clean dry hand over the dried wall. If it feels smooth and leaves no residue, you are ready to fill and paint. If the surface feels tacky, chalky or slick, clean again.
Frequently asked questions
Do I need to wash walls that look clean?
A quick wipe or at least dusting is still worthwhile. Invisible films of dust and oils can affect paint adhesion.
Is sugar soap safe on all paints?
It is commonly used on emulsion and gloss, but it can dull some finishes and should be tested in a small area first. Always follow the product instructions.
How long should walls dry before painting?
Until completely dry to the touch and visibly even in colour, which can range from a couple of hours to a day depending on conditions.