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How to Prep Walls for Painting

Updated: Feb. 27, 2023

Fix any wall before you paint to get a super-smooth finish

Black man painting wall of homeJGI/Tom Grill/Gettty Images
We show you how to fix common wall flaws and make them perfectly smooth before you paint. You'll save the $200 expense of hiring a pro.

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Highlight hidden wall flaws

Highlight wall flaws

Use a strong light to highlight hard-to-see flaws. The shadows cast by small bumps and dents are easy to spot.

The first step to preparing walls for painting is to find and mark any flaws. Minor wall flaws are often hard to spot—until the afternoon sun hits them and makes them embarrassingly obvious. Find and mark any imperfections in the walls. Start by turning off all the lights in the room and closing the curtains. Then hold a trouble light next to the wall and move it across the surface (a process called “raking”).

Wherever the light highlights a problem, even a small one, stick a piece of tape next to it so you can easily find it when you come through with spackling or joint compound. Tape works better than circling the problems with a pencil or pen (which can bleed through the paint).

Video: How to Prep and Paint a Room

We’ll show you how to go about preparing your walls for painting in just one morning – including all that messy clean-up. Your results will rival any painting job done by a pro.

Fix nail pops on walls forever

Pull popped nails

Drive a screw nearby. Then pry out the protruding nail, protecting the wall with a putty knife.

Seasonal expansion and contraction of studs can push nails out of the drywall. You can’t just resink the nail and apply joint compound over the top—the nail will pop back out. To permanently fix a popped nail, drive a drywall screw about 2 in. above or below the popped nail. Use a 1-1/4-in. screw (screws hold better than nails). A longer screw isn’t better—it’s actually more likely to pop out than a shorter one.

Now pull out the nail, holding a wide putty knife under your pry bar to protect the wall. Tap the empty nail hole with the putty knife handle to knock protruding drywall fragments into the wall (or you won’t get a smooth coat of filler on the wall). Finally, cover the screw head and fill the nail hole with three coats of joint compound.

Seal torn paper

Seal tears before applying compound

Prime torn paper edges, sand and then apply joint compound to smooth and hide the flaw.

One important part of preparing the walls for painting is sealing torn paper. The back of a chair, a flying video game remote or an aggressive kid with a toy truck can tear the drywall paper face. A coat of paint or joint compound over torn paper will create a fuzzy texture. For a smooth finish, seal the torn paper.

Start by cutting away any loose paper. Then seal the exposed drywall with a stain-blocking primer. This keeps the drywall from absorbing moisture from the soon-to-be-applied joint compound. Wait for the primer to dry, then sand the exposed drywall edges to remove paper nubs. Cover the gouge with a thin layer of joint compound, feathering it out along the wall. If necessary, apply a second coat, feathering it as well, then wait for it to dry and sand it smooth.

I’m Tip: After applying joint compound, be sure to cover it with primer before painting to prevent “flashing.” Flashing occurs when joint compound absorbs the paint, dulling the finish.

Tape and fill damaged corners

Photo 1: Reshape bent metal corner bead

Shape the corner bead with a hammer until it’s flush with the walls. Don’t worry about making drywall cracks along the corner worse.

Photo 2: Apply tape and compound

Cover the crack with mesh tape, then cover the tape and the corner bead with joint compound. Fill in one side, let it dry, then fill in the other side.

Metal corner bead dents easily, causing cracks in the wall. Fortunately, the fix is relatively simple too. Use a hammer to knock the bead back into shape with several light taps instead of hard blows (Photo 1). Use a level to make sure the bead doesn’t stick out past the finished walls or you won’t get a clean corner (bury the bead in the wall a little if needed). Round any sharp edges on the bead with a file.

When you hit the bead with a hammer, you probably sent cracks up and down the corner, especially if the bead wasn’t taped. Don’t worry; this is part of preparing your walls for painting. Place mesh tape over the cracks, then apply joint compound over the tape and corner bead on one side only (Photo 2). Work on one side at a time—the first side needs to be hard so you can square the other side. Once the first side is dry, apply joint compound to the second side. Then recoat the corner, let it dry and sand it smooth.

Cut around glue spots

Cut out old glue strips

Score the paper with a utility knife, then strip off the old glue.

Mirrors and paneling are sometimes installed with an adhesive backing to help hold them in place. But when you take them down, the glue sticks to the drywall. Don’t try to pull it off—you’ll tear the drywall face, making rips across the wall. Instead, cut around the glue with a utility knife, cutting through the drywall face.

Scrape off the glue with a putty knife. You’ll still tear the paper, but the tears will be confined to the outline you cut in the drywall. Use 120-grit sandpaper on small areas of glue that won’t scrape off. Then, fill gouges that you made in the wall with joint compound.

Fill holes three times

Fill holes

Next, fill holes with filler or drywall compound. Allow to dry, then refill. Avoid overfilling to minimize sanding.

Fill small holes and indents (less than 1/8 in.) with spackling compound. For larger holes, use joint compound instead.

Apply either compound with a putty knife, spreading it thin on the wall. You’ll apply two more coats (the compounds shrink as they dry), so don’t worry if the hole isn’t filled perfectly the first time. Let each coat of compound dry (read the directions; some dry in just two hours).

Don’t believe spackling labels that say you don’t have to sand—you do. You’ll have to sand between coats if there’s any excess compound. After the final coat, use fine-grit sandpaper.

Cut out wall cracks

Photo 1: Cut out loose material

Cut a V-shaped groove in the crack, removing everything that’s loose, even if it means cutting all the way through to the back of the drywall.

Photo 2: Apply tape and compound

Fill the groove with joint compound, cover it with mesh tape, then cover it with more compound.

When homes settle, drywall cracks sometimes shoot out above or below windows and above doors. You can’t just cover or fill the cracks with joint compound—they’ll come back. Instead, fix the cracks with joint compound and mesh tape. Mesh tape gives you less buildup than paper tape and is plenty strong. Protect the window or door trim with masking tape before starting the fix.

To fill the crack, use a utility knife to cut a V-shaped groove along its entire length (Photo 1). Fill the groove with joint compound, let it dry, then sand it flush with the wall. Place mesh tape over the crack (Photo 2). Apply joint compound over the tape and feather it out 2 to 4 in. on each side of the tape. Let the compound dry, then apply a second and third coat, feathering it out 8 to 10 in. from the tape with a 10-in. taping blade.

Fix holes fast with an aluminum patch

Set the patch and apply compound

Cut the aluminum patch oversize, apply it and cover it with at least two coats of drywall compound.

The old method of repairing large holes was to cut out a square in the drywall, attach wood backing and then screw on a new patch of drywall. Aluminum patches (at home centers) are a faster, easier solution of how to repair large drywall holes. They make preparing the walls for painting a breeze. Cut the patch so it covers the hole by at least 1 in. on each side, then place it over the hole. One side is sticky to adhere to the wall. Cover the patch with joint compound. Let it dry overnight, then recoat.

Block stains with special primer

Prime wall marks

Cover wall marks that you can’t clean off with a special stain blocking primer.

Don’t expect regular primer or paint to cover marker or crayon marks; they’ll bleed through even several coats of paint. The same goes for water stains. So, part of preparing the walls for painting is cleaning them off.

First try to wash off the marker or crayon with a Mr. Clean Magic Eraser (at home centers) dipped in warm water. If that doesn’t work, cover the marks with stainblocking primer (KILZ and B-I-N are two brands). Apply the primer with a roller so the texture will match the rest of the wall. Buy a cheap disposable roller and then throw it away when you’re done.

Replace lifting tape

Photo 1: Cut away loose tape

Cut away loose tape with a utility knife. Be aggressive and cut past where the tape has lifted away from the wall.

Photo 2: Add new tape

Place a strip of tape in joint compound a few inches past and directly over the patch. Apply joint compound over the top of the tape.

Tape will lift off the wall if there isn’t enough joint compound underneath to adhere it to the drywall. You’ll have to cut away the loose tape and replace it. Start by cutting through the paint and joint compound to remove every piece of loose tape. Go beyond the cracked area.

Peel away the tape until you see the underlying drywall (Photo 1). Then fill the hole with joint compound and wait for it to harden. Embed mesh or paper tape in joint compound over the hole (Photo 2). Extend the tape a few inches past the hole on each side. Once it’s dry, apply a second coat and feather it to blend the patch with the wall.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Hammer
  • Mud pan
  • Pry bar
  • Taping knife
  • Utility knife
In addition, you’ll need a trouble light.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • Aluminum drywall patch
  • Drywall compound
  • Drywall mesh tape
  • Drywall paper tape
  • Sanding sponge
  • Sandpaper
  • Stain-blocking primer