How To Sand Walls For Painting (A Comprehensive Guide)

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If you are considering painting a room, there are several steps that you must take before you begin painting. It is important to clean, sand, and prime each wall before you ever dip your brush into the paint.

One of the most important first steps is sanding the walls. This article will explain the importance of this process and give tips on exactly how to do it.

The Importance of Sanding Walls Before Painting

Sanding walls is suggested for most walls and is especially suggested for walls that have spackle, bumps, flaws, or old coats of paint or primer. Painting your walls smoothes the surface, which helps the paint stick and makes the final product more aesthetically pleasing.

How Do You Smooth Out a Bumpy Wall?

Smoothing out a bumpy wall is most effectively done through sanding. We will explain how to choose your sandpaper, clean the wall, and smooth it.

Common walls that require sanding are plaster, textured, concrete, and previously painted walls. This is because these materials are often bumpy or uneven and paint does not stick well.

How To Sand Walls Before Painting: A Professionals Guide

1. Choosing The Right Sandpaper

Discuss the best types of sandpaper to use when sanding walls. Are different types better for different stages? (such as for sanding in between coats of paint).

Explain the most important specs to look at when buying sandpaper, such as the size, the grit, etc.

In order to ensure that you properly smooth out any bumps, flaws, or small dents in a wall, it is important to use the appropriate sandpaper. Sandpaper comes in different sizes and grits, which determines how coarse the paper is.

There are several levels of grits, and knowing which to choose when sanding a wall is an important part of the process. Sandpaper that you can find at the hardware store usually ranges from 60 - 80 grit, 100 - 150 grit, and 180 - 220 grit. The higher the grit, the finer the action. The coarsest sandpaper is best for removing previous finishes.

When smoothing out drywall, we recommend a medium-grit sandpaper that won’t clog. Grits 100 and below are too coarse and will scratch or ruin the drywall. These scratches will be visible under paint, so we recommend using grits between 120 and 150.

When sanding walls that have been previously painted with water-based paint, we recommend a finer grit sandpaper. Consider using a grit between 180 and 220. For walls that have been previously painted with oil-based paint, we suggest a medium grit sandpaper. Somewhere between 100 and 150 grit is the ideal range for this project.

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2. Preparing & Sanding The Walls

  • Step 1: Clean the Wall
    It is best to wash the wall with a sponge and warm water to remove any dirt and debris. Start from the top and work your way down the wall. Ring the sponge to make sure the sponge is damp, not wet.
  • Sanding wet walls is not recommended. Washing before sanding eliminates any film or debris that might cause the paint to flake later.
  • Step 2: Gather the Appropriate Tools
    Make sure you have your sanding tool, sandpaper, and any other equipment you are using handy. Wear a double-strap dust mask to keep dust out of your mouth and goggles to keep dust out of your eyes.
  • We suggest a hat or scarf to cover your head to keep dust out of your hair as well. For more information about tools and sandpaper, please refer to the sections above.
  • Step 3: Sand the Wall
    Identify the areas that need sanding. Use a light to find any bumps, flaws, or minor dents that you would like to smooth out, and using your sanding tool, go over these spots until smooth.
  • There is no need to apply excessive amounts of pressure when sanding. Use a light touch to go over problem spots so you do not leave scratches or unwanted marks.
  • Step 4: Apply Primer and Sand Again
    Apply one layer of primer to the entire wall. Once the primer is dried, repeat step 3 in order to get rid of any fuzz or debris left by the primer applicator. You can sand between coats of paint if you would like. 
  • This step is not necessary but can help get rid of fuzz or debris left by the paintbrush and can level any imperfections left by a spray can. There are also unique differences between brushes and spray cans which you should be aware of.

3. How to Clean Walls After Sanding

Sanding creates a large amount of dust, which can cause bumps and imperfections if painted over. To avoid this, clean the wall after you sand this.

Wet a small towel or cloth and ring it out so that it is slightly damp. Working your way from top to bottom, gently wipe the wall to get rid of any dust that sanding caused. Make sure the wall is completely dry before applying primer or paint.

What Happens If You Don’t Sand Walls Before Painting?

Sanding walls before painting them avoids many problems. First and foremost, walls that are not sanded do not hold paint well. Paint can chip easier and often lasts only several years.

It avoids ugly bumps and raised spots on the wall and makes for a more uniform look. Additionally, brushes that apply primer often leave fibers, and sanding is the most effective way to eliminate these fibers for a clean wall and look.

How To Sand Walls For Painting

Different Types of Sanding Tools & Equipment

There are plenty of tools on the market that exist to help you sand your walls. From belt sanders to drywall sanders, we will cover the most common and most effective tools so you can best choose which one works the best for your project.

  • Belt Sander
    A portable belt sander is best for flattening or smoothing wood surfaces. They are the most common sanding tool on the market, and professionals use them to sand large wooden surfaces.
  • Orbital Sander
    Orbital sanders get the job done quickly and efficiently. Their motion is higher per minute than the other popular tools on the market, and they are easy to handle. Orbital sanders are best for finishing large surfaces.
  • Drywall Sander
    Drywall sanders are attached to a long pole, which makes them great for sanding tall walls. They also contain a dust collector, which catches dust while you sand and are the only tool on the market that has this capability. These tools are especially good at removing excess drywall.
  • Hand Sander
    Hand sanders are an affordable sanding tool but are not often used by professionals. They are best at smoothing round edges and fixing smaller portions of drywall. Because they are smaller than the other common sanding tools, they are not the best choice for large areas that need sanding.
  • Sanding Sponge
    Sanding sponges are handheld and meant for hard-to-reach spots and creases in the wall. These are not intended to sand entire walls. Use a sanding sponge to smooth out corners on any wall.

Sanding Walls Before Painting FAQs

Do professional painters clean walls before painting?

Yes. Professionals absolutely clean walls before painting. It is necessary to get any film, dirt, or debris off a wall because anything left will get caught under the paint and can cause bumps or imperfections.

Do professional painters sand walls?

Yes. Professional painters sand walls before painting because it leaves a smoother, more aesthetically pleasing and professional look.

How do you sand inside without making a mess?

Some sanding tools have automatic dust catchers, and there are tools on the market that vacuum the dust as you go. These options tend to be pricier, and we suggest that no matter what option you choose, you wear a mask, goggles, and head covering.

Conclusion

Sanding is an important part of the painting process that should not be ignored. Creating flat, even surfaces before painting a wall ensures a professional look and helps the paint stick long term.

Take a tip from the pros and make sure to properly prepare your walls before painting them. This may take extra time, but it is more than worth the effort if you want clean, smooth-looking walls and paint that doesn’t chip after a few years!