Surface preparation is the most important requirement for achieving maximum durability from any paint system, but the results can be quickly concealed by the first coat of paint, which means negative effects aren’t usually evident until premature paint failure occurs. Before you prepare any surface to be painted, consider the following tips:
The first step
Conduct an examination of the surface and check for peeling or faded paint, dirt, chalking, grease, cracking, knots, bare areas, mildew, rust, nail stains and structural problems. All surfaces, whether painted or unpainted, must be clean, free from shine and dry prior to finishing.
Loose and peeling paint
Remove as much loose and peeling paint as possible by scraping, wirebrushing or powerwashing the surface. Feather-sand rough edges until they blend with the bare surface.
Dirt, grease, oil and chalk
Remove these deposits by washing the surface with a detergent solution or commercial cleaner. Protected areas (such as under eaves and overhangs) need special attention because they carry invisible deposits that can promote premature peeling. After washing, thoroughly rinse the surface with clean water and allow it to dry. Powerwashing is also a fast, effective method of removing dirt, grease, oil and chalk.
Wax migration
If a stain or discoloration persists after removing dirt and/or mildew, it may be a wax migration from the siding. You can identify this problem by applying a few drops of water to a discolored area of the surface and an adjacent non-discolored area. If the water beads on the discolored area but spreads or is absorbed in the areas around the stain, a wax migration condition probably exists. In most cases, this discoloration can be removed with a hot detergent solution followed by a thorough rinsing with clean water.
Cracks, splits and open joints
Any open area from which water can enter should be caulked with a high-quality, paintable acrylic caulk. After this step, apply primer over the caulked area.
Rusty/loose nails
Replace loose nails with slightly larger, galvanized nails or screws. Reset nail heads with hardboard surfaces on all other wood surfaces. Prime nails with a corrosion-resistant primer and fill with epoxy to provide a positive fill.
Previously coated surfaces
Any surface preparation (short of removing all old coatings) may compromise the service life of a new coating system. If you have any doubt about a surface’s ability to be recoated, have a professional check the compatibility of previously painted surfaces by using a test patch with the coating.
