Before you paint, clean the surface to get an idea of how your project will shape up. For paint to perform well, it has to stay on the surface. Paint can’t adhere if the surface isn’t clean.
Clean the Surface
Cleaning a wood surface can be as simple as using a detergent and warm water with a long-handled stiff-bristle brush. Work in sections from top to bottom. Thoroughly rinse off the soap residue. Don’t soak the wood, because some wood may warp.
As each area is finished, rinse the surface and do a test swipe with your hand. If there is still dirt or a chalky residue, wash and rinse again.
If the project is large or the surface is particularly dirty, consider using a power washer, but be careful. While power washers can quickly rid large surfaces of dirt, they must be used with caution. Follow operating instructions to prevent injury and to avoid damaging or saturating the wood or shattering nearby glass.
If mildew—a brown, black, gray or spotty fungus—is present, a solution of household bleach and water may be needed. Brush the solution on, let it work for about 15 minutes, and rinse it off. If using a power washer, use the ingredients specified by the manufacturer.
Wood needs sufficient drying time. Paint will fail if it is applied to saturated wood. One sunny day will usually dry a wood surface. If the wood is saturated, it may take several windy or sunny days before painting can begin.
Examine the Project
Determine the steps needed by first examining the project. Check for signs of problem deterioration – bubbling, cracking, or peeling. The source of the problem needs to be investigated and corrected.
If the previous coat of paint is in good condition, allow the wood to dry. Consider sanding the old paint if the previous surface was glossy. Sanding to a lightly dulled finish will help the new paint adhere better. Use sandpaper to feather the edges of the old coat of paint. Brush or wipe away any dust from sanding.
If there are any areas where the paint is gone and the wood is exposed, treat the wood with a water-repellent preservative and allow it to dry thoroughly before priming.
If the exam reveals more serious paint problems, the old paint needs to be removed and the cause of the problem investigated. A paint job fails for several reasons, according to the U.S. Cooperative Extension Service. Outside moisture or inside water vapor moving through the house walls may have penetrated the wood, causing blistering and peeling.
Oil-base paints subjected to the heat of the sun within a few hours of being applied may have blistered. Peeling and cracking paint usually means there was too much time between a primer coat and the top coat. Cross-grain cracking typically happens when too many coats of paint have been applied.
Removing problem paint gets complicated if the old paint contains lead. Lead paint is more likely to be found in homes built before 1978. If there is a chance that this paint-stripping project involves lead paint, call the National Lead Information Center or contact a local paint retailer about how to safely strip and dispose of lead paint.
After the cause of the paint problems has been corrected, it’s time to remove the old paint. Several options are available. Scraping with putty knives or scrapers or sanding by hand are the most common. Other options include power washing, wet sandblasting, orbital sanders, stripping with chemicals, and using electrically heated paint removers. Each carries its precautions.
Power washing and wet sandblasting can dig holes in the wood surface. Orbital sanders require a dust-collection vacuum. Chemical strippers can be fast-working but are hazardous to the user and the environment. Heated removers can easily ignite surrounding materials. Peel-away strippers work well but are slower and may require a neutralizer to remove any residue.
Wood Surface Repair
After the surface has been cleaned and the damaged paint removed, check the condition of the exterior wood. Damaged areas need to be fixed or replaced. Decayed wood that is soft or spongy will never hold paint and should be replaced. For small holes or cracks, paint with a spot primer and then fill with a liquid wood, water putty, or acrylic caulk labeled for exterior use. For larger areas of deterioration, it’s better to replace than repair.
Before painting, dust all surfaces, use painters tape to protect adjacent areas where paint is not wanted, and use drop cloths to cover any plants or shrubs.
Credit: Renovate Your World