Western red cedar that has been finished with paints or solid-colour stains is best refinished with the same type of finish originally applied. These finishes are sometimes used interchangeably but old latex coatings should always be refinished with latex coatings and never with oil-based coatings. Old oil-based finishes can be refinished with latex finishes only when the old oil-based finish has been properly cleaned and a primer coat applied first. Remember, that proper surface preparation and cleaning before refinishing are essential for optimal performance of the new finish coat or coats.
To refinish the old surface, first scrape away all loose, cracked or peeling finish. Sand the bare wood and any remaining finish to “feather” the edges smooth with the bare wood. Mildew must be killed and removed before western red cedar is refinished, or the mildew will grow thru the new paint coat or solid-colour stain. Removal can be done with a commercial mildew remover or mix oxygen bleach crystals, such as Oxiclean, with warm water and spray on affected area. Let the chemicals work for about 20 minutes and agitate with a bristle brush, then rinse with a garden hose. Allow the washed surface to dry thoroughly before recoating and apply primer paint to areas of bare wood. After the primer has dried, apply one or two topcoats of paint or solid-colour stain. Two topcoats are always better over bare wood that has been primed.
Weathered water-repellant preservative finishes should be cleaned with a non-ferrous bristle brush to remove loose fibres and dirt. If the surface is soiled, it may be scrubbed with a mild soap solution. If mildew is present, it should be killed with an oxygen bleach solution. After that, the surface should be thoroughly rinsed and allowed to dry completely before refinishing. Important: Do not use ferrous wire brushes for surface preparation.
Caution: Never mix bleach with detergents containing Ammonia, as the fumes can be harmful.