How To Clean Walls Before Painting
Whether you are DIY-ing or hiring professional painters, cleaning walls before painting is an important step to ensure a quality paint job.
The easiest way to clean walls before interior painting is to use a slightly wet sponge with warm water and dish soap to wash the wall surfaces. Mixing a few tablespoons of baking soda with hot water also works.
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Clean your walls from top to bottom using a sponge mop with an extension handle in a circular motion. Alternatively, you can use a damp cloth as well.
If cleaning multiple rooms, I would also change out your bucket with clean water in each new room. Lightly rinse the walls with clean water afterward for best results.
Step-By-Step Wall Cleaning Per Room:
- Pour a gallon of warm water into a bucket with a few drops of dish soap detergent or a few teaspoons of baking soda as needed.
- Use a damp sponge mop or rags to clean walls from top to bottom. Scrub stubborn stains with a degreaser solution mix or magic eraser.
- Rinse any cleaning solution used on the walls with warm water.
- Dry any damp areas with clean rags or clothes, make sure to wipe baseboards, and avoid excess water or drips. Use a fan to circulate air and reduce dry times.
How To Test If Walls Are Ready To Paint
A good test to see if walls are ready to paint after cleaning is to apply painter’s tape to the wall surface.
If the tape adheres, your walls are ready for a coat of primer or paint. But if the tape doesn’t stick, you’ll need to rinse the remaining cleaning solution residue off or wait longer for the walls to dry.
Generally speaking, avoid using any heavy-duty cleaning products or trisodium phosphate to clean interior walls. It’s not only overkill but may produce harmful odors if air circulation is limited.
Finally, don’t use any type of acidic cleaning products like vinegar or CLR and other tub or tile cleaners.
Highly acidic cleaning products can react with the old paint to damage the walls and cause adhesion issues.
How long do old paint cans last?
Wall Washing Supply Checklist
When washing walls, a few drops of light detergent or soap in a bucket of warm water should be plenty.
Also, make sure to wring the sponge before scrubbing the walls to avoid excessive water drips.
Here is a basic checklist of items you’ll need to wash your walls before painting:
- Empty Bucket
- Clean Rags or Sponge Mop
- Warm Water (not too hot)
- Dawn Dish Soap or Mild De-Greaser
- Small Ladder or Step Stool
- Dry Rags for Excess Water
- Vacuum with a Soft Bristle Attachment
- Fan for Faster Drying
Most importantly, be careful to not over-wet the wall surface and avoid using too much dish soap in your cleaning solution.
This can ruin the walls or surrounding trim and force you to replace the water-logged drywall.
In any case, wipe down any excess water or moisture with dry rags to avoid these costly damages.
Last but not least, wait a few hours or a day for the walls to completely dry before painting. Use a vacuum to clean up excess floor dust and a fan for more air circulation to dry surfaces faster.
Washing Walls is Overkill For Most Paint Jobs
However, using a wet sponge to wash walls before painting is overkill unless you have extremely dirty walls coated with grime or oil.
In most cases, you simply use a duster to remove dust or cobwebs before applying new paint. Likewise, you can use a Mr. Clean magic eraser to easily remove scuffs and crayon marks.
After dusting, use a damp cloth or microfiber rag to clean any remaining dust, making sure to not over-wet the surface.
For oily kitchen walls, use a light degreaser in their cleaning solution to remove grease stains.
Sometimes, you might need to use an oil-based paint or primer to prevent future stains from coming through.
Having said that, scuffing walls to ensure adequate adhesion is an extra step that is often missed by homeowners who tackle DIY wall painting projects.
Next, we dive into how and why the best professional painters perform this crucial interior wall cleaning step to virtually guarantee a quality finish.
What Rooms Typically Need Walls Washed?
The dirtier and dustier your home is, the higher the chance that you’ll need to wash your walls before painting.
Likewise, if you have a ton of furniture and trinkets around the house you’ll likely need a deep cleaning of the wall surfaces before painting.
Similarly, you’ll likely want to clean your walls before painting if you have a lot of pets that shed or children.
However, if you regularly clean your house monthly or hire a cleaning service to clean every two weeks, you should be okay with skipping a full wall wash down.
In reality, certain rooms in your home may require wall cleaning and others may not.
For example, living rooms, dining rooms, office areas, and primary bedrooms typically don’t need wall washing with detergents.
On the other hand, higher-traffic spaces like bathrooms, kid’s bedrooms, mudrooms, kitchens, hallways, and entryways might need a good cleaning of the walls before painting.
Overall, most rooms don’t need a full wall scrub unless they are super dirty or grimy. That’s one of the reasons why most professional painters do not do a full wash down of walls before painting.
Do Professional Painters Wash Walls Before Painting?
In most cases, professional painters don’t wash walls with a detergent solution to avoid damaging the drywall or trim.
Instead, most professional painters lightly sand or “scuff” the walls with a pole sander using fine-grit sandpaper. Typically, using 100-grit or 150-grit sandpaper works best to prep walls for painting.
Lightly sand the walls in a circular motion using a pole sander, starting from the top and working your way down to the baseboards. Learn how much professional painting contractors charge per day on average in our new article!
Sanding walls before painting not only removes grime better than a wet sponge or soapy water but also increases paint adhesion by removing the previous paint’s sheen.
Even flat or matte paints contain a slight sheen or shininess. By all means, sanding the old paint with fine-grit sandpaper creates a better surface for any type of paint to adhere to.
After lightly scuffing the walls, painters use a damp rag with warm water to wipe down any extra dust that sanding kicks up.
Remove All Mold Before Cleaning Walls
For walls with mold, use a bleach and water solution to remove mildew stains before painting.
Indeed, mold on walls will permeate through the new coat of paint. Since latex paint doesn’t adhere to moldy surfaces well, failing to remove it will lead to blistering or peeling.
Removing these mold spots with a sponge soaked with four-part water, and one-part bleach solution will do the trick.
Again, use warm water in a bucket and change out with clean water in each room for best results.
Lastly, wear plastic gloves and goggles when cleaning with bleach. Additionally, lay down a drop cloth or plastic film to protect surrounding floors. Discover how to match paint colors and wood floors like an interior designer pro!
As with any home improvement project, safety comes first so avoid DIY-ing any painting of walls with black mold.
For black mold or very moldy wall areas, you may need to hire a mold remediation company to completely replace the drywall before painting.
Use Oil-Based Primer To Remove Heavy Stains or Smells
Before painting, use an oil-based primer like Kilz or Zinnser to cover walls with heavy stains in rooms previously occupied by smokers.
A few coats of stain-blocking oil primer will work wonders to remove smells and cover heavily stained walls.
I would also use an oil-based primer on walls, ceilings, or trim that had any kind of mold on it previously. Learn all about when to prime walls in our primer paint guide!
Accordingly, the oil-based primer will not only kill any remaining mold spores after cleaning but also increase top coat adhesion.
Another instance where I would use oil-based primer is for walls with large drywall repairs, cracks, or holes to be patched.
After patching with putty, I would lightly sand the surface and spot-prime with an oil-based primer to help block any flashing through the new paint colors.
Cleaning Trim or Baseboards Before Painting
Baseboards, door casings, window sills, and horizontal interior trim surfaces usually get dustier than vertical walls over time. Cleaning trim surfaces before painting is incredibly important for a crisp, clean finish.
And since most interior trim is white or off-white, it will show grime and dust more if not properly cleaned.
Luckily, it’s rather easy to clean because trim surfaces are typically finished in a semi-gloss or gloss sheen. In general, the higher the paint sheen, the easier it is to clean.
Conversely, wall paints are usually a matte, satin, or eggshell finish and are harder to clean. What’s the difference between matte and satin paint?
For trim and baseboards, I typically recommend using something like a Swiffer wet duster sheet to remove grime and dirt before painting.
Also, “scuffing” or lightly sanding trim before painting is recommended because of the surface’s high sheen. Correspondingly, scuffing will allow the paint to better bond to the shiny trim surface.
Cleaning Walls Before Painting FAQs
The following are a few of the most asked wall cleaning questions we’ve gotten over the years from homeowners and professional painters.
Should I paint over wallpaper?
No, we do not recommend you paint over wallpaper. In general, wallpaper removal or installation is one of the hardest DIY home improvements you can take on.
Even if you manage to remove most of the old wallpaper, you’ll have to deal with remaining glue residue and damaged walls.
As a result, we recommend hiring a professional wallpaper specialist or painting contractor that does wallpaper for these types of projects.
What is the best thing to wash walls with before painting?
The best thing to use when washing walls is a pole sander with finer-grit sandpaper. Pole sanding your walls before painting removes stains, grease, and dirt effectively. Plus, light wall sanding increases paint adhesion and coverage.
After sanding the walls, use a damp rag to wipe away any remaining dust and wait for the surface to completely dry before painting or priming.
While you can use a damp sponge or cloth to wash the walls, this technique is often overkill and can even damage and warp your interior walls or trim. Reserve a wet wash down for extreme cases or very dirty rooms.
In this case, you can use a light detergent like Dawn dish soap combined with warm water to wash the walls with a damp sponge or rag.
Can I use TSP when cleaning interior walls?
No, you should not be using trisodium phosphate to clean interior walls unless you are a professional.
While TSP can etch shiny paint finishes and remove mold, the risk of damaging floors, tiles, or surrounding fixtures is too high. Likewise, TSP is caustic and causes health issues when used indoors without protective equipment or ventilation.
Rather, TSP is best used for exterior painting projects like removing mold from wood siding with a power washer. Find out which exterior paint colors will be trending this season.
What type of paint works best for interior walls?
Our expert painters recommend using high-quality water-based latex interior paint from either Sherwin Williams or Benjamin Moore when painting interior walls. We put these two most popular interior paint brands to the test in our latest article.
While Behr, Valspar, or PPG paints from Home Depot or Lowes hardware stores have gotten better over time, they still aren’t as good as other brands.
For higher-end finishes, Farrow and Ball could be a good choice. Just remember that their paints are more expensive and harder to work with than your average interior paint.
How To Clean Walls Without Removing Paint?
If you need to clean very dirty walls before painting, use a light detergent like dish soap mixed with warm water. You don't need a ton of soap to do the trick, just a few drops is enough.
Avoid using vinegar or de-greaser on latex painted walls as it will remove the finish and create issues when you apply a new coat of paint.
Furthermore, use a soft sponge or rag instead of a coarse sponge or wire brush.
Walls previously painted with oil-based paints are a bit more forgiving when using de-greaser but I would still avoid scrubbing too much or you risk removing the paint altogether.
Instead, lightly sand the walls with 100-grit or 150-grit sandpaper to clean the surface or remove grease stains. This is what professional painters do to achieve a silky smooth finish after the final coat of paint dries.
