How to Prepare Concrete Surfaces for Painting

Check your surface for water issues first. Get any leaks or seepage problems fixed before you start. Paint will never dry on damp cement. If the floor has gotten soaking wet, let it dry out for up to a month before painting. A dehumidifier will help and so will fans or blowers. Rushing this process will ensure a ton of work later on, so make sure the surface is really dry.

Clean your concrete surface thoroughly. Sweep or vacuum well, then inspect the surface for stains. If there's grease or oil, cat litter will absorb damp grease or oily residue. Sprinkle the litter, let it sit for an hour and sweep it up.

Clean any remaining grease and oil with a cleaner designed for use on concrete. Several brands are available in any home improvement store. One common cleaning ingredient is tri-sodium phosphate, also known as TSP. Be sure to follow all label instructions.

Check your clean surface for irregularities. Patch any cracks and smooth out the surface. Sand any bumps or unevenness down flat. If you need to patch anywhere, follow the instructions about drying times carefully. Don't proceed until the floor is completely dry.

Roughen up the surface you want to paint with a wire brush or a hand sander with 80 grit sandpaper. A light sanding will do, but make sure to sand the entire surface. Sweep and damp mop.

Paint the floor with a primer. Use a primer made for stain blocking. You will probably need two coats to do a thorough job. Let this also dry completely. You floor is now prepped for painting.