Cedar is a popular material for shingles and siding because natural oils in its heartwood (the dark red wood at the center of the tree) make it resistant to the weather and hungry insects. Even unpainted, cedar will last for years. Painting cedar, however, calls for some preparation.
Some sections of old, unpainted shingles and siding may look darker than others. This discoloration is most likely caused by a combination of excessive tannins leeching from the wood and mildew growth. You'll have to remove the mildew and prime the wood with a stain-blocking primer. You can prime and paint new shingles as soon as you have installed them, but since weathering can quickly alter the paintability of wood, if you don't get to the job within two weeks, you'll have to recondition the wood fibers. Powerwashing old shingles is not recommended. Weathering makes them soft, and it's almost impossible to avoid gouging them and to properly dry the water forced under them.
What You Need
- Large sponge
- Garden hose
- 4-inch brush
- Old paintbrush
- Stiff scrub brush
- Household bleach
- Stain-blocking primer
- Acrylic exterior paint
How to Paint Old Shingles
Step 1: Clean Shingles
Survey the entire area of your house, especially the lower levels, where the shingles will more likely retain water. Wherever you find mildew, sponge on a 1-to-3 bleach-water mixture, scrub it, and let it soak in for 20 minutes, keeping it wet during this period.
Step 2: Rinse and Let Dry
Using a garden hose with a moderate spray, rinse off the bleaching solution thoroughly. Let the area dry completely, which can take as much as two weeks.
Step 3: Brush Surface
Recondition the entire surface to remove aged and weathered fibers in the wood. Use a stiff scrub brush, working the bristles into the overlapped edges along the bottom of each course and drawing the brush down the face of the shingle. Brush off the dust with an old 4-inch paintbrush.
Step 4: Apply Primer and Paint
Using a 4-inch brush, apply an oil-base stain-blocking primer. Work the brush into the overlapped edges and the recesses between the shingles. Let the primer dry and apply a high-quality acrylic latex house paint. If you roll either primer or paint, back brush so all surfaces are protected.
How to Paint New Shingles
Step 1: Prime Shingles
Within two weeks of their installation, prime the shingles with a stain-blocking primer. (If you wait longer than that, recondition the surface as shown in step 3 above.) Apply the primer with a 4-inch brush, starting along the overlap and painting a length of about 4 feet.
Step 2: Paint
Once you have primed a section of the overlap, paint the face of the row, working the paint in all directions and between the shingles. Smooth the application with downward vertical brush strokes and repeat the process on the next section, always working toward a wet edge.
If you choose to spray either primer or paint on your shingles, apply the coating evenly and from different angles. Work in sections of about 20 square feet and backbrush the coating immediately so it gets worked into the shingle fibers and the recesses between them.
Staining Cedar Siding
Staining cedar siding differs from application of paint and other finishes. Stains dry rapidly, and fresh stain applied over dried stain will show lap marks.
First remove any mill glaze (a hard shiny surface on one side of the siding) by sanding. If possible, stain all sides of the siding before installation. Working in tandem with a helper or working alone, stain one length of siding from end to end before moving down to the next board.