Sanding walls before painting is a crucial step with any painting method but it becomes even more important if you’re using a paint sprayer. Unless you are painting a popcorn ceiling, you will want the surface underneath to be as flat and clean as possible.
Besides sanding the surface, any holes or cracks should be covered, too. For that, you have the choice between painters putty vs spackle and we recommend painters putty for a smoother surface.
Sanding Walls Before Painting
Read on for our how-to guide on sanding walls before painting so you can get pro results with your paint sprayer.
Why Is Sanding Walls Before Painting Necessary?
We have to sand a wall before starting the painting process to get the smoothest finish. It can be a time-consuming job but the final results are worth it.
Sanding a wall before painting is part of the cleaning process. It takes away any bumps and impurities which would otherwise cause an uneven painted surface, even if you are using the best paint sprayer for walls or a basic roller.
You can always tell when an uneven surface was painted because you will see darker and lighter patches on the wall. It also creates an inconsistent texture, an unintentional one, that is.
Besides a less professional finish, it is also more costly to paint an uneven wall. To make up for the uneven finish, you will have to use extra layers of paint to make up for the difference.
Paint layers are generally very thin anyway so you can imagine how many extra layers you will have to add to make the surface seem smooth. Not only is this more expensive but it is also time-consuming.
In short, it is better to spend a little extra time prepping a wall for painting instead of having to spend time and money on having to cover up the impurities later.
- Several sheets of sandpaper of different grades
- Sanding block or tool*
- Cleaning solution
- Safety goggles
- Mask or respirator
- Work gloves
- Filling knife
- Masking type
There are several sanding tools available, both manual tools and electric tools. The most basic option is a sanding block which is basically a rectangular wood block that you wrap the sandpaper around.
The advantage of using a sanding block is that you get a better grip and simply flip to another side once the used sandpaper side is used up. However, these blocks don’t sit as comfortably in your hand.
There are also sanding boards with a handle but it is more difficult to make circular motions with these tools. The fastest and least straining option is using an electric sanding tool but these cost more.
The final choice is up to personal preference. Professionals and those with large scale DIY projects will prefer an electric sanding tool because they get the job done faster but the manual tools can get you good results, too.
How to Prep a Wall by Sanding
Step 1: Prepare the room for painting by removing as much furniture as possible and covering the furniture that cannot be moved. Also, cover the floor with drop cloths and cover moldings, switches, window frames, handles and so on with masking tape.
Step 2: Dust all the surfaces to be painted with either a cloth or a long duster that lets you reach up high.
Step 3: Prepare the sugar soap solution in the bucket. Soak up some of the solutions with the sponge before using it to clean the walls.
Sugar soap is the preferred cleaning solution for prepping walls for painting because it does not leave residue. However, make sure to use the solution sparingly because you don’t want wet streaks on the wall either.
Step 4: Let the soap solution sit for a few minutes per the instructions on the package. In the meantime, wash out the used bucket and refill it with regular tap water.
Step 5: Using a new sponge, wash down the wall using plain water. Again, make sure that the sponge is only moist and not so wet that it will leave streaks on the wall.
Step 6: Let the wall dry while preparing the sanding tool. This step will differ depending on which type of tool you use.
When using a sanding block, wrap the sanding paper around the block. You will have to hold it in place with your hands (wearing gloves, of course).
Most sanding boards have a feature to attach the sanding paper, such as clips, for example. Electric sanders usually have a velcro layer to keep the sanding paper in place.
Step 7: Choose the right sandpaper for the surface and the step in the process. The differences in types of sandpaper and grit are explained below.
When prepping a wall for painting we generally recommend a softer sandpaper to avoid damaging the wall. If there are rougher patches on the wall use an 80 grit but generally, a 100 is enough for preparing a wall before painting.
You might also want to finish off the wall by sanding it again after painting. For this use a 240 grit or even higher.
Step 8: Work in circular motions when sanding the walls. This creates the smoothest surfaces and makes damage to the surface less likely.
Different Types of Sandpaper
Sandpaper is a simple material but knowing how to use it properly requires knowledge of the differences. We could write a complete guide on sandpaper explaining the different grits, materials, and purposes.
To keeps things simple, understand what grit means. Grit refers to the size of the ‘sand’ or synthetic material used to make the paper rough.
The general rule of thumb to remember is that the higher the number the larger the grains and the softer the sandpaper. There are two measurement systems with the CAMI scale being the most common in the US and the FEPA scale in Europe.
Always check whether the sandpaper is described in CAMI or FEPA before purchasing.