A fresh coat of paint can completely transform a room—but learning how to prep walls for painting will make your paint job look showroom-new for years to come. Before breaking out the roller and brushes, get ready to clean your walls and sand away imperfections. This guide will walk you through wall preparation for painting to get that perfect finish.
Why Should I Prep Walls Before Painting?
You might want to skip the extra step, but wall prep is essential for a smooth, long-lasting paint finish. Paint won’t properly adhere to a dirty, unprimed surface, which welcomes unsightly cracks, bubbles, and chips. Beyond that, wall prep fixes surface imperfections like nail holes, dents, and deep scratches, so you’re getting more than just a fresh coat of paint—you’re getting a space that looks brand new.
Before You Start Prepping Walls for Paint
Mildew and Flood Damage
Painting won’t solve a mold or mildew problem. In fact, painting makes it much more difficult to remove because mildew can grow right through a fresh new coat. In other words, if you don’t get rid of mildew during the wall prep stage, you’ll need to repaint sooner than later.
Luckily, a bleach-based mold and mildew cleaner should do the trick. Let the cleaner sit for a few minutes to penetrate the mildew, then scrub it away with a scrub brush.
“After an area is cleaned, I recommend priming the area with an oil-based primer to
ensure the affected area is sealed,” says Nick May, Angi Expert Review Board member. “You can use Kilz or another oil-based primer sealer for this step.”
Lead Paint Safety
Wall prep is a fairly straightforward process, but it can be a little messy. Sanding produces dust—and if you’re sanding down lead paint, take precautions for lead paint safety. Luckily, this is generally only an issue in homes built before 1980. In that case, you might want to hire a local lead testing company just to be sure.
Either way, wear a dust mask and safety goggles at a minimum. Move furniture out of the room or cover it with plastic sheeting, and always tape up vents to prevent dust from spreading throughout your home. Having your vacuum handy can help you clean up dust as it piles up.
Clean the Walls
Paint won’t adhere well to a dirty surface. You’ll need to get rid of dust, dirt, and grime—which could include tackling sticky kitchen grease or removing cigarette smoke residue. Fortunately, washing your walls doesn’t take much sweat equity. All you need is some warm water and a scrubby sponge.
If walls are particularly dirty, you can ramp it up a notch with an all-purpose cleaner or degreaser that’s safe to use on painted walls. Don’t forget to clean the trim and moldings thoroughly. If you’re having trouble reaching or plan to paint your ceiling, attach your sponge to a telescoping handle for extra length.
How to clean walls before painting depends on how you use the room. Kitchens need a little more elbow grease to eliminate the literal grease from cooking. You may have to clean some mildew or mold in the bathroom that you won’t typically find in other rooms. This informs the type of products you should use to clean the walls. You may want to use:
Degreaser for kitchen walls
Mold and mildew remover for bathrooms and other moist areas
All-purpose cleaner for general cleaning
“The average bedroom takes one to two hours to prepare, and a family or living room will take slightly longer, likely two to four hours,” says May. “Not all walls need to be sanded or cleaned, but many kitchen walls do. If you live in the western half of the U.S., most walls have significant texture (orange peel or knockdown) and require little to no surface prep. All rooms require covering of floors or furniture.”
Always choose high-quality primer and paint for rooms that experience temperature fluctuations. To get a perfect finish, plan your project based on the weather. For example, if you don’t have air conditioning, avoid painting on a hot and humid day, or the paint could bubble.
Sand It Out
Photo: Thomas Barwick / DigitalVision / Getty Images
After you’ve washed your walls thoroughly, the next step for painting your walls and trim is to give them a good sanding with 80- to 120-grit sandpaper. However, sanding your walls is only necessary if you repaired significant drywall damage or your walls were previously painted with a semi-gloss paint. If you have textured walls, sanding is typically not needed. The other reason for sanding is if the previous paint had a lot of contaminants, resulting in bumps.
The goal is to get rid of any chips, knicks, divots, and deformations that might have accumulated on your walls in high-traffic, high-use, or high-humidity environments. Primer also adheres better to a textured surface.
Before you get your sanding on, it’s a good idea to cover doorways, HVAC registers, sinks, and fixtures with plastic sheeting. The last thing you want is to spoil your brand-new paint job with sinks and heating grates clogged with dust.
Fill In Marks on Your Walls
Sanding isn’t always enough to get the smooth surface you need for a pro-quality finish. Pictures, decorations, and shelving can leave deep holes and divots in your walls. Luckily, with some DIY drywall repair tips, you can fill in these stubborn imperfections with some spackling paste.
Apply the paste per the manufacturer’s instructions. Once the spackle is dry, give your wall a light sanding with 220-grit sandpaper. Anything heavier is likely to leave streaks. Use circular motions to get the perfect canvas for your paint.
Tape It Up
Before you prime or paint, you need to cover the areas you don’t want to paint. Make sure to give all your surfaces a final wipe-down with a damp cloth to remove any residue or debris from cleaning and sanding your walls. Then, cover outlets, trim, floor, and any other surface you don’t want primed and painted with plastic sheeting and painter’s tape.
Choose the best tape for your wall surfaces and for the length of time the tape will be left on. “Use a low-tack tape for any previously painted surface. Use a delicate
tape for any recently painted surface or surface that could peal up (like wallpaper or
paper-coated cabinet),” May says. “Only use masking tape on carpets or other surfaces that require more adhesion and cannot be damaged.”
Once you’ve cleaned and sanded your walls, there’s one last step you need to take before getting your color groove on. You guessed it: primer. Paint primer is important if you have drywall or you’re painting in a humid area prone to stains (think: kitchens, bathrooms, or laundry rooms).
First, drywall is naturally porous, and primer helps stop bleed-through and uneven coverage and coloration. Second, humid environments are prone to bubbling, peeling, and cracks. You’ll need the paint to adhere as much as possible.
DIY vs. Hiring a Pro
It’s probably obvious by now that painting your walls is a little more involved than just slapping on some color. Most homeowners can roll up their sleeves and do the job with a little elbow grease. Depending on the finish and color, it could take some trial and error—but it’s definitely doable. If you’re doubtful or want to spend your weekends enjoying your space rather than painting it, contact an interior painter near you to freshen up your walls.
Frequently Asked Questions
You need to wash your walls before painting. Washing walls is a crucial part of the painting process. If you don’t wash your walls, trapped mildew can grow through the paint, essentially ruining your brand-new paint job. Your paint will also struggle to adhere to a dirty wall, so it could crack, bubble, or peel.
You can generally paint over old paint as long as the wall doesn’t need repairs and you’re using a paint that’s chemically similar (for example, latex paint over latex paint). This gets tricky depending on the shade, especially if you’re going lighter. It’s best to use a primer to cover the old color before painting.
After cleaning, you generally need to wait for one to two hours for your wall to dry before you can paint. This changes with the weather. It will take longer for your wall to dry if it's super humid. To be safe, set up some fans, and let your wall dry overnight.