It is a good practice, to clean your deck once a year, in the spring, to remove dirt, mildew and other forms of discoloration. Yearly cleaning will ensure that the deck looks nice as well as prolonging the life of the protective coating. Scrubbing your deck with warm soapy water will remove dirt, but diluted household (oxygen based) bleach will be required to remove mildew, as mentioned above. Most coating companies also manufacture deck cleaning products to complement the deck finishes they manufacture. These products called cleaners, brighteners or restorers remove different forms of discoloration without stripping the finish from the Western Red Cedar. Most of these cleaners can remove dirt and discoloration caused by mildew and algae from the surface of cedar, but they vary in their ability to remove iron and tannin stains and weathered (grey) wood from the surface of the deck. Some of these deck cleaners may actually remove wood from the weathered cedar surface and therefore you should take care when using them. Power washers can seriously damage cedar deck surfaces and, as mentioned above, this type of cleaning is NOT recommended for cedar decks or any other cedar product.
Deck surfaces should be refinished when the Western Red Cedar starts to lose its color.
The new finish needs to penetrate into the wood. Finishing too soon leads to inadequate absorption; finishing too late means the coating may have been applied to weathered wood, which reduces the performance of finishes. The first step in refinishing a Western Red Cedar deck is to clean it (as above). After the deck surface has been cleaned and rinsed down it should be allowed to dry. The moisture content of the wood should be below 20%.
Refinishing the deck with semi-transparent stain or transparent stains and water-repellents is relatively easy as the finish can simply be reapplied using a brush, pad or roller, as above. The stain will easily penetrate some areas of the deck surface which have become more porous after weathering. In other areas, there may be a tendency for the finish to sit on the surface of the wood. Try to prevent this occurrence by removing the excess finish with a brush. If you apply too much stain when refinishing your deck, the stain will form a film on the surface and will behave like a paint requiring more extensive maintenance (stripping of the finish) in the future.
It is difficult to maintain the original natural look of Western Red Cedar exposed to the weather over a prolonged period of time. The more natural and transparent the finish, the more difficult it may be to retain the original color of the wood. Eventually you may decide to completely strip the weathered finish from the surface of your deck and start from scratch. In this situation, you can use a heavy duty cleaner/stripper that will remove the stain from the wood as well as discolored and weathered fibers. However, you should be aware that it is quite difficult to completely restore the cedar to its original appearance. Commercially available stain-strippers will remove oil-based stains and acrylic stains from finished Western Red Cedar. Most are supplied as ready-to-use liquids. After use, residual cleaner or stripper should be thoroughly rinsed from the wood surface and the wood should be allowed to dry before any other coating is applied.