How to Clean Decks and Remove Stains and Discolorations

Lumber doesn't fare well unprotected. The sun's ultraviolet rays are always on the attack, breaking down lignin, the polymer in wood that gives it rigidity. Rain and sun swell and dry wood, eventually causing it to crack and split. Moisture promotes the growth of mold and mildew. Dirt lodges between wood fibers and sticks to treatments ( coatings) you may apply.

Difficulty: Moderately Easy

Instructions

1. Before applying a treatment to a new deck, be sure that its moisture level is stabilized (usually about a month after installation). Older decks must be cleaned of mildew and dirt first. Clean and treat older decks at least once every three years. To determine if small black spots are mildew, drop full strength household bleach on one; if it disappears after a minute or two, its mildew. To eliminate mildew on a larger area, use 2 to 3 ounces of TSP household liquid bleach or a phosphate-free substitute mixed with a gallon of water. Use a stiff brush to scrub the area, and rinse it after 15 minutes.

2. For routine cleaning of decks to remove dirt and mildew ( or on new decks, to remove mill residue), wash with oxygen-based bleach from the paint store, applied with a pump sprayer.

3. For redwood and cedar, use oxalic acid deck cleaner rather than bleach to remove graying and stains. Follow the instructions and cautions on the label. After cleaning, allow the deck to dry for 72 hours, then treat the deck.

4. Deck-treatment products may be solvent or water based, and some are applied in a two-step process; a base coat followed by a top coat within a year. There are several main categories of deck-treatment products.

5. To Remove Stained & Discolorations on a Deck:
   
   Scrub immediately with a detergent that contains a degreasing agent.Set-in stains may require a light hand-sanding with a very fine sandpaper. The sanded area will stand out at first but will weather to match the surrounding wood. Commercial deck cleaning agents and powders or liquid concentrates from a home center or hardware store have a base of chlorine bleach, non-chlorine bleach, or oxalic acid and may include detergent. Bleach based products eliminate mildew and graying. Acid based products eliminate graying and some stains.Some products may darken woods such as redwood and cedar,so be certain to test any material in an inconspicuous place.

[justforkids]

on 10/8/2009 Great info and easy steps

[kda2007]

on 9/18/2009 Thanks - I have deck that needs some help.