Preparing Interior Surfaces For Paint

Preparing your interior walls correctly in my opinion is the most important part of a painting project. If the walls are not prepped right, the final paint job will look amateurish.

Prepare interior walls, ceilings, and woodwork by washing them with a solution of TSP and water. Then patch all cracks and holes. Do not paint wallpaper with an oil-based paint. If the paper adheres well and is smooth, a latex primer and paint will probably cover it satisfactorily. If not, scrape off the wallpaper or rent a steamer to soak it off.

When covering an enamel-paint surface, add some tooth for the new paint. Sometimes TSP will degloss the enamel sufficiently. Otherwise, roughen it by sanding with medium-grit paper, using a circular motion. Used an oil-based primer and either an oil-based or latex top coat.

If layers of paint obscure details in the woodwork, you may want to strip the paint. Complete stripping is desirable if you refinish the wood with clear sealers; partial stripping will be adequate if you cover the trim with new paint. If you are lucky, you will be able to strip the wood with scrappers and sandpaper. If not, you will have to use a chemical paint remover, following the instructions on the can. You will need lots of newspapers, rags, steel wool, and ventilation.

If you can find new molding with a pattern similar to the painted molding, replacing the trim may be easier than stripping. Finish by removing all light fixtures, electrical cover plates, doorknobs, and other hardware.

Patching deep cracks. It is tempting to patch plaster walls and ceilings with a superficial coat of patching compound. Don't -- the cracks will almost certainly open up again. To do the job properly, widen the cracks as well as making them deeper.

Using a pointed object, such as a can opener or crack-opening tool, remove enough plaster to make a V-groove approximately 1/4-inch deep. Protect your eyes with goggles and blow out all dust and debris.

Moisten the cracks with a plant sprayer and apply patching compound with a putty knife. Use a wide blade for multiple cracks. Most compounds will shrink slightly when they dry, so you will have to apply a second coat. Sand as necessary.

Patching hairline cracks. Where multiple hairline cracks have developed, (especially on ceilings), a fiberglass mesh will save you from having to open the cracks. Spread a thin coat of compound over each crack then imbed the mesh into it. Cover it with a final layer of compound. Feather the compound at the edges so it blends into the surrounding area. Mix in some sand or texture the patch to match the rest of the ceiling.

Patching holes. Remove all loose plaster, being careful not to separate sound plaster from the lathe. Wet the lathe and apply a coat of plaster or patching compound about 1/8-inch below the finish surface. Score the wet patch with a nail. After the first coat dries, apply a final coat of compound. Feather the edges, and stipple this last coat with a brush so that it matches the surrounding area.