How to Prep Interior Walls for Painting, Step by Step

Ask any experienced painter what makes a paint job look professional and the answer is almost always prep. Paint doesn't hide much. It shows the holes, cracks, and bumps underneath, sometimes more clearly than before. The good news is that prep isn't complicated. It mostly takes patience.

This guide walks through how to prep interior walls from start to finish. The steps apply to most drywall in most homes. If you live somewhere humid, like the Tampa Bay area, a few extra details around moisture and mildew make a big difference too.

What you'll need

You don't need a lot of special equipment. A typical prep kit includes:

• Drop cloths and plastic sheeting
• A screwdriver for switch plates and outlet covers
• A work light or bright flashlight
• A bucket, sponges, and a mild cleaner
• Spackle for small holes, and joint compound or a patch kit for larger ones
• Putty knives in a couple of sizes
• Sanding sponges or sandpaper in medium and fine grits
• A tack cloth or damp microfiber cloth
• Paintable caulk and a caulk gun
• Primer, including a stain-blocking primer if you have stains
• Painter's tape
• A dust mask and safety glasses

Before you start: two safety checks

Lead paint. If your home was built before 1978, older layers of paint may contain lead. Sanding or scraping lead paint creates hazardous dust. Test first with a lead test kit or a professional test. If lead is present, follow lead-safe work practices or hire a company that holds EPA lead-safe certification.

Moisture and mildew. If you see mildew spots, peeling paint, or soft drywall, look for the cause before you paint. In Florida homes, that's often a bathroom without enough ventilation, an AC condensate line leak, or a roof leak. Painting over an active moisture problem won't fix it.

Step 1: Clear and protect the room

Move furniture to the center of the room and cover it with plastic or drop cloths. Lay drop cloths along every wall. Take down wall art, mirrors, curtains, and blinds. Remove switch plates and outlet covers and keep the screws with each cover.

Clearing the room properly makes every later step faster and cleaner.

Step 2: Inspect in raking light

Hold a work light or flashlight close to the wall and shine it along the surface at a low angle. This "raking light" makes every dent, hole, crack, and bump easy to see. It's the same effect afternoon sun has on your walls, and Florida homes get a lot of that.

Mark each problem with a small piece of painter's tape so you don't miss anything.

Step 3: Clean the walls

Paint sticks best to a clean, dull surface. Dust walls and baseboards with a dry cloth or vacuum brush, then wipe them down with a mild cleaner and water. Rinse with clean water and let the walls dry completely.

Kitchens tend to have grease near the stove. Bathrooms may have soap film or mildew. Hallways and light switches collect fingerprints. Spend a little extra time on those spots. For mildew, use a cleaner made for it and follow the label directions.

Step 4: Patch holes and dents

For small nail holes and dings, press spackle in with a putty knife and scrape it flush. For larger holes, use joint compound or a patch kit. Apply thin layers, let each dry, and build up gradually rather than filling in one thick pass, which can crack or shrink.

If you find popped nails or screws, drive them back in or add a new screw nearby, then fill over them.

Textured walls are harder to patch invisibly. Small repairs can often be blended with a light touch, but larger patches on knockdown or orange-peel texture may take practice or a pro. Our guide to hiring for drywall repair covers what that work involves.

Step 5: Sand and remove dust

Once patches are completely dry, sand them smooth and flush with the surrounding wall. Run your hand over the area; you should feel no ridge. Lightly scuff any glossy surfaces, like old semi-gloss paint, so the new paint can grip.

Then remove the dust. Wipe walls with a tack cloth or a damp microfiber cloth. Dust left behind will show up as grit in your finish.

Step 6: Caulk gaps

Look for gaps between baseboards and walls, around door and window trim, and at inside corners where hairline cracks sometimes appear. Run a thin bead of paintable caulk, smooth it with a damp finger or caulk tool, and wipe away the excess. Let it dry as directed on the tube before painting.

Caulking is one of the small steps that makes a room look finished.

Step 7: Spot-prime

Primer helps paint cover evenly and bond well. Spot-prime every patch and any bare drywall. Patches that aren't primed can show through as dull spots, sometimes called "flashing."

Use a stain-blocking primer on water marks, marker, crayon, or smoke stains. Otherwise they can bleed through several coats of paint.

Consider priming the whole wall when you're making a big color change, painting over glossy paint, or painting new drywall.

Step 8: Tape and do a final check

Apply painter's tape along baseboards, door and window trim, and the ceiling line if you're not painting the ceiling. Press the edge down firmly with a putty knife or your fingernail to keep paint from seeping under.

Then do one last pass with your raking light. Touch up anything you missed. When the walls are clean, smooth, primed, and taped, you're ready to paint.

A note on humidity

In humid climates, drying times on the label can stretch. Joint compound, caulk, and primer may need longer than expected, especially on muggy days. Running the AC and a fan helps. Don't rush to the next step until each one is fully dry.

Prep or hire?

Prep is where most of the time on a paint job goes, whether you do it yourself or hire someone. If you'd rather hand it off, our interior painter hiring guide explains what good prep should look like in an estimate. When you're ready, you can request a free estimate from a local painter listed on CityPaintPros. For more projects, visit the DIY hub.