Installation, Care, and Maintenance of Wood Shake and Shingle Siding tells the homeowner how to finish cedar siding. Solid-color stains (also called solid-body stains or opaque stains) are available in oil- and latex-based formulations.They give more protection against UV radiation than semitransparent stains. However, solid-color stains do not penetrate wood; they form a film just as paints do. To get good service life, they need to have sufficient film thickness to avoid failing by flaking and peeling. Prior to application, it is best to prime shakes or shingles with a stain-blocking primer prior to applying a solid-color stain to avoid extractives bleed. These stains perform best on textured or rough surfaces, but should not be used on a weathered surface.
Paint is a film-forming opaque finish and provides the best surface protection against water and weathering. Good quality stain-blocking primers applied to all surfaces prior to installation offer the best protection against discoloration by water-soluble extractives. (See discussion of back priming in Factory Finishing section.) Top coat with good quality acrylic latex-based paint. As with solid-color stains, paints will not adhere to weathered surfaces.
Caution: The use of transparent film-forming finishes such as urethane varnish, lacquer, conventional varnish, and shellac are not recommended for exterior use. Ultraviolet (UV) radiation can penetrate these types of finishes and degrade the wood. The finish will become brittle, then develop cracks and peel from the surface. Paint manufacturers continue to improve the UV radiation resistance of these products. It may be possible to get 2 to 3 years of good performance with finishes formulated with some of these new products, particularly on structures having moderate protection from sunlight (single-story structures having wide roof overhangs and/or shaded by trees).