How To Clean Walls Before Painting

If you’ve ever painted a room before, you know that quality tools and time are essential to a great paint job, but before you begin painting, there’s a very important step: cleaning. 

Many people skip this step and head straight for the paint rollers; however, painting over the dust and grime on your walls can cause major headaches later. Clumps of dust trapped in paint globs, mold, mildew, and blistering paint will require you to completely start the project from scratch or even require professional repairs. 

Don’t put extra costs on painting when you don’t have to. Our advice is to skip the hassle of a do-over and take the trouble of washing the walls before painting.

Table of Contents

• How to prep a room before painting
• Which walls need cleaning before painting
• Cleaning with TSP before painting
• Cleaning walls with smoke stains
• Cleaning walls with mold and mildew

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How to Clean Walls Before Painting

Before we get into the nitty-gritty of washing the walls, there are a few steps before we reach the cleaning and painting. Doing the prep work on the front end ensures the project runs smoothly and efficiently.

Here’s how to prep a room before painting:

• Remove or cover furniture and the flooring with a drop cloth to prevent paint spills and drops.
• Remove everything from the walls, including photos, small nails, light switches, and outlet covers. Store all these items in a singular, safe place to easily find them later.
• Patch nail holes and imperfections ahead of time and allow the putty time to dry. After you’ve patched, sand down the areas to be sure the filler is completely flush with the wall. Any rough or raised spots will show through the new paint.

Once all patching and sanding are done, it’s time to clean the walls. Rooms exposed to smoke, grease, and other products that leave behind a residue will need the most attention. Other rooms may need a quick dusting with a Swiffer Dry Cloth along the walls.

Which walls need cleaning before painting?

If you are painting a low-traffic room, like a living room or home office, your walls may not need a deep cleaning as a kitchen or bathroom may. However, if you’ve patched or sanded anywhere in any room, we highly recommend wiping the walls with mild soap and water to remove dust particles.

• Kitchen Walls – With the steam, food splatters, spills, and splashes, your kitchen walls have a fair amount of grime. This room requires heavy-duty cleaning with a TSP mixture or a similar product.
• Bathroom Walls – Sticky residue from hairspray, perfumes, and other products tend to collect along your walls, leaving behind a film of gunk. 
• Bedroom and Living Room Walls – Because these rooms have the least amount of activity, they don’t need quite as much cleaning action. A light wipe-down with mild soap and water will suffice. Be sure to remove any dust and cobwebs, too!

Cleaning walls with TSP before painting

For heavy-duty cleaning, we recommend using a product called TSP (Trisodium phosphate), a chemical cleaning compound great at cutting through years of grime and dust to prepare a nice clean surface for painting the adhere to.

TSP can also be used to clean out dried, used paintbrushes, degrease metal parts, or scrub a grimy floor or bathtubs – so it is a handy cleaning agent to keep around!

Keep in mind that TSP should never be mixed with any other cleaning agents, especially bleach.

Combine the TSP and hot water in a bowl or bucket, and use a rag or sponge to wipe down the walls, trim, and baseboards. Be sure to ring the rag out well so there’s not too much liquid running down your walls.

After cleaning, rinse the areas using a clean rag and water.

Since this is a very potent chemical, be sure to wear gloves when cleaning with TSP.

If TSP is banned in your state, substitutes are available. But at the very least, clean the walls well with a wet rag before painting to remove dust.

Cleaning walls with smoke stains

Smoke stains discolor paint and leave behind a foul odor that paint cannot cover up. Smoke odors seep into the walls and require heavy-duty cleaning. 

For smoke-free walls, use a mixture of baking soda and water. The mixture removes smoke stains and neutralizes the odors.

We also recommend using a high-quality primer, like this, before painting if your walls have any smoke stains.

Cleaning walls with mold and mildew

Paint can hide a lot of things, but mold and mildew aren’t one of them. You should never, ever paint over mold and mildew. These two bacteria will continue to grow and spread underneath the paint and peek through the layers. 

Mold is a scary word when it comes to homes. Here’s what you need to know. A little bit of mold on a wall or in the corner of the shower is fine. It’s an easy fix to clean.

To get rid of mold and mildew, mix three parts water and one part bleach and apply with a rag or sponge. Then, rinse thoroughly with a clean, damp cloth.

Note: If the area that contains mold exceeds more than 10 square feet or so, it’s best to call in a mold removal specialist because it may be evidence of a larger issue in your home (like a bathtub leak).

Most importantly, no matter what cleaning method you use to wash your walls before painting, allow the walls to dry thoroughly before painting. Otherwise, the paint may blister and peel.

Before you paint your next room, don’t forget to clean the walls before painting using one of the methods we explained in this article:

• Mild soap and water for standard walls with a little bit of dust
• TSP for cleaning dirty walls (like a kitchen or bathroom)
• Baking soda and water combination for cleaning smoke stains (also don’t forget to prime first!)
• Bleach and water combination for cleaning up mold and mildew

Making sure your walls are clear of dust, oils, and grim is an important step and will ensure that your paint adheres and is long-lasting!

How to Clean Walls Before Painting

Active Time: 30 minutes

Total Time: 30 minutes

Difficulty: Easy

Estimated Cost: $20

Knowing how to clean walls before painting is vital for your end result. Washing your walls before that first coat of paint is time-consuming, but it will prevent cosmetic issues, paint blemishes or chipping, and even health issues down the road. Here’s how you should wash your walls before you begin painting.

Print

Materials

• TSP (Trisodium phosphate)
• Gloves
• Cleaning bucket
• Cleaning rag or sponge

Instructions

Heavy Duty Cleaning

1. For heavy-duty cleaning, combine TSP and hot water in a bowl or bucket.
2. Wipe down walls, baseboards, and trim. Ring out rag or sponge so there isn't a lot of water running down the wall.
3. Allow are to dry completely before painting to avoid blistering or peeling of your new paint.

Cleaning Smoke Stained Walls

1. To clean smoke stained walls, use a mixture of baking soda and water. The mixture will remove smoke stains and neutralize orders.
2. Wipe down walls, baseboards, and trim. Allow to dry completely before painting.

Cleaning Mold and Mildew

1. To remove mold and mildew, use a mixture of three parts water and one part bleach.
2. Apply with a sponge or rag.
3. Then rinse thoroughly with a clean damp cloth.

Recommended Products

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  Sunnyside 64216 TSP Tri-Sodium Phosphate All Purpose Cleaner, 1-Pound