Exterior Solid Color Stains: Latex or Oil
No matter what anyone tells you, wood will not "drink up" the oils in a stain and restore life to the siding. The wood is dead. You are coating it for a good appearance, low maintenance, and a longer lasting finish.
Solid color stains, also called heavy bodied stains, are opaque finishes which come in a wide range of colors and are defined as stains. Solid color stains are made with a much higher concentration of pigment than the semi-transparent penetrating stains. As a result they tend to obscure the natural wood color and grain.
- Oil-based solid color stains tend to form a film much like paint and as a result can also peel loose from the substrate, though less than oil based paints.
- Latex-based solid color stains are also available and form a breathable film as well as oil-based solid color stains. These stains are similar to thinned paints, however tend to peel less as they are not grabbing as hard.
Solid Color Stains may be applied to a smooth or lightly textured surfaces by brush, pad, spray, or roller application, but brush application is best. These stains act much like paint. One coat of solid color stain is adequate, but two coats provide better protection and longer service. Unlike paint, lap marks may form with a solid color stain.
Latex-based stains are faster drying and therefore more likely to show lap marks than the oil-based stains. Lap marks are prevented by staining only a small number of boards or a panel at one time, maintaining a wet edge. This method prevents the front edge of the stained area from drying out before a logical stopping place is reached. Working in the shade is desirable because the drying rate is slower.
One gallon will usually cover about 250 to 400 square feet of smooth surface and from 150-200 square feet of rough surface. For long life with oil base stain on rough sawn or weathered lumber, use two coats. One coat is normally not sufficient. Avoid intermixing different brands or batches of stain. Even if they appear alike when new, they will differ with age. Always stir stains thoroughly during application. Sponges or cloths that are wet with oil base stain are particularly susceptible to spontaneous combustion. To prevent fires, bury them, immerse them in water, or seal them in an airtight container immediately after use.
Latex stain can be applied over freshly primed surfaces and surfaces where an oil-base stain has already been used and weathered. Where old surfaces are to be re-coated with latex a simple test should be conducted first. After cleaning the surface, paint a small, inconspicuous area with latex stain, and allow it to dry at least overnight. Then, to test for adhesion, firmly press one end of a "band aid" type adhesive bandage onto the painted surface. Jerk it off with a snapping action. If the tape is free of paint, it tells you that the latex paint is well bonded and that the old surface does not need priming or additional cleaning. If the new latex paint adheres to the tape, the old surface is too chalky and needs more cleaning or the use of an oil-base primer.
Textured plywood surfaces are common for exterior siding. Sanded and roughsawn plywood will develop surface checks, especially when exposed to moisture and sunlight. These checks, coupled with the flat grain pattern (wide bands of dark, dense late wood) characteristic of nearly all plywood, can lead to early paint failure. These paint failures can be minimized by the use of top quality acrylic latex stains.
Paint Versus Stain
In some cases, painting of plywood is required or desirable. Top quality acrylic latex paints are the best choice for exterior surfaces. For overlaid or MDO plywood, remove all loose paint with a stiff bristle brush and then scrub with a soft brush or sponge and water. Rub your hand against the cleaned surface to determine if any residues remain. When necessary, scrubbing with a detergent or paint cleaner will usually remove additional residues. Then rinse well and allow to dry before repainting.
If non-overlaid plywood is to be painted, follow these tips. First, brush a liberal quantity of water-repellent preservative or water repellent onto all the edges of the plywood sheets. The surface should also be treated in the same manner. The water repellent will help reduce wood's tendency to absorb moisture through the end grain and surface lathe checks.
Allow the water-repellent preservative or water repellent to dry for at least two warm days. Then, prime the plywood surface with a high-quality paint recommended for use on woods that contain extractives. The primer should be applied thick enough to obscure the wood grain pattern. Two coats of a high-quality acrylic latex house paint should be applied over the primer.
Allow at least two days but no longer than two weeks between the primer and top coat. The primer and top coat should be compatible and preferably from the same manufacturer. Always remove the mildew before refinishing. Refinishing painted plywood requires proper surface preparation if the new paint coat is to give the expected performance. First, scrape away all loose paint. Use sandpaper on any remaining paint to "feather the edges" smooth with the bare wood. Then, scrub the remaining paint with a brush or sponge and water.
Household bleach (based on sodium hypochlorite) used at the rate of 1 cup of bleach to 3 cups of water will remove mildew. Rinse the surface with clean water. Wipe the surface with your hand. If the surface is still dirty or chalky, scrub it again using a detergent or paint cleaner. Rinse the surface thoroughly with clean water, and allow it to dry before repainting. Areas of exposed wood should be treated with a water-repellent preservative or water repellent, and allowed to dry for at least two days and then primed. One or preferably two top coats should follow.
Now you can make an informed decision on whether to choose a latex or oil solid color exterior stain. Now comes the hard part, the painting!