Q: My redwood deck is about 2 years old and needs a good cleaning. Which product would you recommend to clean a redwood deck and what sealant should I use? I like a clear, natural finish.

A: You’re right at the outside edge there. If a redwood deck gets a fair amount of sun, it should be cleaned and resealed at least every second year. If it’s mainly shaded and you haven’t developed mildew, you can get by with doing it every three years. Cleaning and sealing should be viewed as a regular maintenance program and will prolong the life of the deck as well as maintain its look.

Although we’ve addressed this subject many times, a quick refresher course is in order.

For longevity and aesthetics, apply a preservative to outdoor wood. It can either be semitransparent stain or clear preservative. While stain will change the color of the wood, a clear preservative will darken and enrich its natural color. An example is redwood, which is a light red, almost pinkish color in its freshly milled state but turns to a deep red rose when treated with most preservatives.

Many companies make sealants and stains for outdoor wood. Some of the better-known brands are Cabot, TWP, Defy and Armstrong. For a clear finish, our favorite has always been DuckBack’s Superdeck, a sealer that offers protection from the sun’s ultraviolet (UV) rays. But we recommend you do your own research by going to deckstainhelp.com and clicking on "product reviews."

Frequency of sealing depends on exposure to weather and use. A maintenance program consists of cleaning the deck, removing any mildew, and applying a new coat of preservative.

Although we continue to believe that the best way to clean a deck is with a pressure washer, a stiff-bristle brush and plenty of elbow grease will do the job, especially if cleaning is done regularly. Think about going to the dentist to have your teeth cleaned. The job is a lot easier and less painful if it’s done at regular intervals.

A pressure washer sends out a pressurized fan of water that makes short work of surface dirt, mold and mildew. These machines are available at rental centers and can be purchased at home centers. If you get along well with your neighbors, consider getting two or three of them to chip in on buying one and then sharing it.

We recommend using a pressure washer that can produce a stream of water of at least 1,500 pounds per square inch (psi). Be sure to keep the wand moving so you don’t blast softer wood away from the surface and leave a rippled effect on the deck. Deck cleaners formulated for use with pressure washers are available where the machines are rented or sold.

If you go the brush route, use a stiff-bristle brush and deck cleaner mixed in a bucket of water in the proportions the manufacturer recommends. Use a brush attached to a broom handle to save wear and tear on the back and knees.

In shaded, moist areas, mildew can be a problem. Wash with a weak bleach solution — 1/4 cup of bleach to a gallon of water — to kill the fungus before pressure washing or scrubbing.

Once cleaning is completed, thoroughly rinse the deck with clear water and allow the deck to dry for several days. Then brush, roll or spray a coat of UV protective water-repellent sealer or stain. We found some excellent "how to" videos on the Superdeck website.

So, to sum up:

  • Pressure wash your deck rather than sanding it.
  • Clean and treat your deck with a preservative every two years.
  • Remove any mildew by pressure washing thoroughly.
  • Use a pressure washer with at least 1,500 psi.
  • Use the fan setting on the nozzle and keep it moving to prevent a ripple effect.
  • Use a chemical deck cleaner for really bad decks.
  • Apply sealer or stain.
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