Seven Misconceptions About Finishing Wood Decks
Here are some common misconceptions about finishing wood decks that we have encountered over the years.
- Misconception # 1 – Wood decks are maintenance free.
In the good old days cedar and redwood came mainly from old growth trees that were primarily hardwood – that part of the tree containing high levels of resins and oils which are naturally resistant to decay and insects. Construction today is from younger, second growth trees which have a higher sapwood content and are less resistant to biological enemies. In any case, all redwood and cedar is susceptible to damage from rain and sunlight. The best way to avoid this damage is to apply a protective finish before it occurs.
- Misconception # 2 – Surface preparation isn’t needed before recoating weathered decks.
Surface preparation removes stains and deposits which would otherwise be sealed in with the coatings. Also, importantly, it prepares the wood to be a sturdy anchor of the applied finish. Washing the deck with water alone or detergent and water is not enough. This will not remove mildew, algae, and grayed weathered wood. The best way to prepare a weathered deck for recoating is by using a commercial deck brightener/restorer and pressure washing. This removes not only dirt but mildew, algae and gray UV-damaged wood.
- Misconception # 3 – Bleach is great for cleaning decks.
When used on decks, bleach-based products can do more harm the good. Not only are they ineffective in removing dirt, surface deposit, gray and UV-damaged fibers – they can leave the deck with a whitish’ unnatural tone due to the bleaching out of components in the wood. Treatment with hypochlorite-based products can also result in premature graying of the wood.
- Misconception # 4 – New wood should be allowed to weather or season for several months before finishing.
Recent research by the U.S.D.A. Forest Products Laboratory has shown that exposing unprotected wood to weathering for even a few weeks can cause surface damage which can result in premature failure of subsequently applied coatings. New decks should be protected as soon as possible after construction. The quickest way to protect new wood is with the application of a water repellent finish.
- Misconception # 5 – All finishes are pretty much alike.
There are more deck coatings on the market today than ever before. There are, however, important differences in the type and quality of deck finishes of which the educated consumer needs to be aware. The higher quality water repellent formulas will contain a mildewcide to protect the coating from surface mildew growth. These finishes are designed to keep new wood looking new and to help restore the new look to grayed wood. They often contain amounts of pigments and oils to impart a natural tone to the wood and help protect against UV damage. The higher quality finish in addition to containing UV blockers, are formulated to contain water repellents and EPA-registered wood preservatives. The wood preservative ingredients will help fight mildew and decay.
- Misconception # 6 – Paints and solid color stains offer the best protection to wood decks.
Paints and solid color stains are generally not suitable for horizontal substrates subject to the weather, such as exposed deck and porches. The film-forming properties of these paint and coatings work against them in these situations. Penetrating semitransparent stains and water repellents finishes, on the other hand, do not generally peel or blister as they age. They fade and erode off the surfaces as they weather, making recoating a much easier task. Wood is a dynamic substrate. Since these penetrating semi-transparent stains do not form discreet films, they are better able to move and breathe with the wood during the weathering cycles.
- Misconception # 7 – When it comes to coating, more is better.
A major source of problems and complaints for all wood deck finishes is over application. As noted above, most deck finishes are designed to penetrate into the wood rather than form a film on top. Over-application of water repellents can result in a surface which is waxy and slippery. Over-application of stains can result in a sticky surface. For most deck finishes, one coat is usually sufficient.