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How to Prep Walls for Painting

Updated on July 17, 2012

Preparing Walls for Painting

If there is one thing most people hate about house painting, it's the preparation. If you want your newly painted walls to look flawless, wall preparation should be about 80% of the job and the remaining 20% for painting. Holes in drywall, stains and other defects are pretty easy to fix and make a huge difference in appearance after repainting everything.

Remove Furniture

The more working space, the better. Move furniture to the middle of the room, so there's enough space to work on the walls. Throw a big sheet of plastic over the furniture for protection against sanding dust and paint. You can also use old bed sheets that you don't plan on using anymore, or a clean plastic tarp.

Plug In A Halogen Work Light

If you really want to fix every single defect on the wall, a halogen work light is best. The bright lighting makes it easier to spot holes, grooves and bumps in need of repair. A work light usually comes on a stand, big or small, but you can buy a smaller hand-held light. Walk around the room and circle wall repairs with a pencil. Do not use a pen.

Scrape the Wall

I like to do any necessary scraping before I mix up any joint compound for patching. That way the walls are 100% ready to be patched with joint compound and it will be easier to fill every hole and crevice before the compound dries in the pan. Use a taping knife to scrape, or a 5-in-1 tool.

Scrape torn drywall so the edges aren't loose or sticking above the surface. You can also peel off loose pieces with your fingers. Remove wall nails and screws that won't be reused after painting the room. Scrape over the nail and screw holes to level the surface. For drywall paper protruding from wall holes, tap the holes with the butt of the scraper to knock the paper below the surface.

Nail pop bumps should also be scraped off and repaired properly. Most people tighten the existing drywall screw and fill the hole, but eventually, it will loosen and pop out again. The best way to fix it for good is to completely remove the loose drywall screw and drill in a new screw right next to the old one. Then fill both holes when you patch the walls.

Sand the Wall

Wear a respirator before sanding. A dust mask is fine too, but a respirator is better. Sanding dust is really bad for your lungs. Most paints contain silica particles which can cause serious respiratory problems, such as Silicosis.

Beware of Lead Paint

If your home was built before 1978, DO NOT sand or scrape the walls - there could be lead paint underneath. Instead, buy a lead tester kit at the paint store and test the walls for lead before doing any work. If the walls do contain lead, it is highly recommended that you either consult a lead certified paint contractor, removal expert or simply paint over the walls without doing any sanding or scraping.

To sand walls, use a sanding head. It screws onto the end of a painting pole (extension pole). Attach a sheet of sandpaper to the sanding head and sand the walls from top to bottom to remove bumps and any roller hairs stuck in the existing paint finish. For really glossy walls, use coarse sandpaper, such as 80-grit to dull and de-gloss the surface for the new paint. Sanding the walls not only makes the surface smooth, but allows the new paint to stick better.

Prime Walls for Painting

If there are water stains, crayon marks, traces of mildew, nicotine stains or torn drywall, you will need to use a good primer sealer to block stains and prevent wall bubbling from ruining the new paint finish later. I highly recommend an oil-based primer for blocking tough stains and sealing drywall. Kilz is the best. It reeks, but it's one of the best.

Torn Drywall

If you see brown paper where the drywall is torn, it absolutely needs to be primed. Do not paint or even patch over the brown torn paper without priming it first. The water in the joint compound, as well as the water in latex paint, will make the brown paper bubble and peel, ruining your newly painted wall.

If there's only a couple small areas with torn drywall, buy a spray can of oil-based (alkyd) Kilz and spray it. If the entire wall is a torn up mess then you'll probably need to buy at least 1 gallon and roll out the entire wall to completely seal it. Wear a respirator and open the windows. After the primer dries, sand it and begin patching with joint compound.

Repair Walls with Joint Compound

The best joint compound is SheetRock that comes in a bag. The powder is a little messy when mixing it, but it doesn't shrink like wall spackle does and it dries fast so you can start sanding and painting sooner. Mix the compound in a mud pan.

Nail and Screw Holes

Fill the nail and screw holes, but for small holes like this, use a putty knife. For bigger and deeper holes, it may be necessary to apply a second coat of compound to level the surface nicely.

Big Cracks

If those big cracks on your walls keep coming back after you fill them in, you need to do a little more work to fix the problem once and for all. The best way to repair big cracks is to place fiber glass drywall tape over the crack and patch it with joint compound.

First, lightly gouge the entire length of the crack and scrape off any loose paint chips around the edges. Next, fill the crack with compound, allow it to dry and place a piece of fiber glass drywall tape directly over the crack. Apply 2-3 coats of joint compound over the tape, sand the patch and paint. The crack won't come back anymore.

Clean the Walls

After all that sanding and scraping, the walls are going to be filthy with dust and debris. Wipe the walls with either a tack cloth, or a damp rag, to remove the dust. Vacuum the dust on the floor so it doesn't end up in your lungs or on the freshly painted walls during clean up.

This article was written by Matt Goetz, owner and founder of Advantage Painting Services in Crystal Lake, IL. Our company provides interior and exterior house painting services in Mchenry County. For more information, check out our About Us page.


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    • Matt G. profile image

      Matt G. 5 years ago

      Thank you.

    • profile image

      Ed 5 years ago

      Clearly explained, good job.