How to Seal a Cedar Shake Roof

Cedar shingles have been used as a roofing material for hundreds of years. One reason for this is that cedar wood contains natural preservatives that keep the wood slightly pliable and water-resistant for many years. However, what many homeowners seem to think is that once it's installed, their cedar roof needs no maintenance, and unfortunately this simply isn't true. Sunlight and rain bleach and wash out the natural preservatives in the wood, and water enters the cells of the wood and causes it to swell, then dry and shrink. Cracks develop. Mold and fungus begin to grow. In short, your cedar roof needs lots of care to keep its appearance and its usefulness. But beware --- cleaning and sealing a cedar roof is dirty and dangerous work. It is easy to slip and fall, especially if your roof already has lots of slippery fungus or mold. If you are unsure whether you're up to the task, hire a professional who carries sufficient insurance to do the job for you.

Power washer
TSP
Bleach
Semitransparent cedar sealer
Sprayer

Instructions

- 1
  Wet the roof thoroughly before attempting to clean it. It is important that the cells of the wood be expanded and filled with moisture before you attempt the cleaning process --- the first step in sealing the roof. Wash the roof with a power sprayer set no higher than 1,200 psi, and do not get the tip closer than 12 inches to the shingles, or they could become damaged. Also, it is imperative that you work from the topmost part of the roof and wash downward. Never attempt to wash "upward" on the roof, or water will be forced under the shingles, and the possibility of damage to the roof is greatly increased. Use extreme caution, as the roof could become slippery, increasing the risk of falls.
- 2
  Clean the roof with a combination of TSP and bleach. Add 1 cup of TSP cleaner and 1 cup of bleach to the power washer, and clean your roof when it is still wet. Again, work from the top of the roof downward, do not use more than 1,200 psi of pressure and do not put the tip of your wand closer than 12 inches to the shingles to prevent damage. Wet all of the boards with the TSP/bleach solution, taking care not to slip and fall. Allow the roof to dry completely before proceeding. This could take two to three days.
- 3
  Seal the dry roof with a semitransparent sealer designed specifically for cedar shingles. Follow all the manufacturer's instructions completely, and use the type of sprayer that the manufacturer recommends for applying its product. Start at the top of the roof, and spray the sealer on every exposed part of the wood. Spray in light coats until the cells of the wood are filled. Do not apply so much sealer that it begins to drip and run down your roof. Do not apply sealer if rain is expected or possible within 24 hours. Allow the sealer to dry completely.

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