DIY Network

Deck Care and Waterproofing From "Ask DIY Home Improvement" episode DADH-201

Figure A

Q: (from Cameron in Knoxville) I'm sending you pictures of my deck. It looks awful. What can I do to make it look better?

A: (from DIY woodworking and refinishing expert Bruce Johnson) From the photos (figure A), it does appear that your deck is in pretty bad shape. It looks like you've got pressure-treated lumber -- which is good -- but it doesn't look like anything's been done to it. There's mold and mildew, and possibly some rot.

Materials:

Deck wash
Wood protector
Paintbrush, roller or sprayer
Scrub brush
Garden hose
Rags

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• Here's a simple test that anyone can do to the wood on their deck to see if it's in need of help. Sprinkle a few drops of water onto the surface of the wood. If the water beads up, as seen in the section of our sample-board that's been treated with a finish (figure B), then the wood is still retaining water-resistant properties.

• If the water soaks in within about 15 seconds, as seen on the untreated portion of our sample board (figure C), then it's time to take some action. If rainwater is soaking into the wood, it causes the fibers to swell -- which accelerates the breakdown of the wood. In situations like this, some deck protection is in order.

  Figure B

  Figure C

  
  

  Figure D

• In this case, the first step will be to clean the deck's wood surfaces to clear away the layers of mold and mildew. For this, you'll need a deck wash. These products are easy to apply. They are designed to clean the surface and bleach or remove mold, mildew and other discoloration. Follow the manufacturer's directions for your product. Typically they can be applied with a brush, roller or sprayer. Apply the product liberally, allowing it to soak well into the wood.

• Once it has been applied, come back with a scrub-brush or synthetic pad use it to loosen the mold, mildew and dirt that has built up on the surface of the wood (figure D).

• After scrubbing, wash the surface using a hose and fresh water. If you want, you can wipe the surface with a clean, dry rag.

• Important: Allow the deck wash to dry for two days -- so that the bleach has time to evaporate completely -- before the next step.
  

• Once your deck has been cleaned, you can apply a wood protector finish to the bare wood. You may opt for a tinted wood protector (figure E), that adds some pigment along with the protective seal.

• Or you may choose a clear wood protector (figure F), that maintains, but accentuates, the basic natural color of the wood.

• As with the wash, you can apply the finish with a brush, roller or sprayer. The key is to apply one thin, even coat on the deck. This type of product is less effective if it is loaded too heavily onto the surface.

• A note on new decks: Wait about thirty days before applying a wood protector to a new deck. The chemicals used in pressure-treating lumber require that time to evaporate. After the wood treatment has had that much time to cure thoroughly, a finish can be appled.

  Figure E

  Figure F