Cedar Shingle Discoloration
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Natural Water-soluable Extracts
One characteristic of Western Red Cedar is the presence of water-soluble color extractives, which may "bleed" out onto the surface and discolor white or light-colored paints. This is neither a fault of the wood or paint formulation, but rather an indication of the presence of moisture in the wall. This moisture may come through the surface of the paint if the film has fractured; or it may enter through cracks, apertures or other defects in the construction; or it may arise within the building and be carried through the walls.
No change in type of paint, or similar approach will be successful in dealing with the problem unless the source of the moisture is located and cut off. Insufficient ventilation of some homes is the major problem, as substantial quantities of moisture are produced and retained by improper venting of vapor-producing appliances, inadequately louvered attics and crawl spaces, poorly installed insulation and vapor barriers.
Initial Waiting Period
If a small amount of bleeding occurs during the first year, it is worthwhile waiting through this "shakedown" period because these surface deposits usually either weather away or can be washed off by using soap and water, or a stronger detergent if needed.
Latex Paint Surfactants
Surfactants leaching from latex paint is often confused with cedar extractives. Surfactants are water-soluble ingredients in paint that can come to the surface and will have a brown, blotchy appearance. These paint components appear when cold or humid conditions occur before the paint has fully cured. The surfactants can typically be washed off the surface and should not affect the performance of the paint.
Mildew which appears as dark patchy areas is often mistaken for staining or bleed through. See our information page Cedar Shingles and Mildew for a simple test to identify mildew. If it is present, mildew should be treated at once.