The ins and outs of cleaning a deck or patio

Your deck and patio may need attention now that the harsh winter is over, and the last thing you want to do is cause them even more harm. Unfortunately many homeowners damage their wood decks and patios by using the wrong cleaning products and cleaning methods.

STEP 1: Consider discarding all information stored in your brain about how you've cleaned wood decks, docks and outdoor patios in the past. Most of the information that's been published is not correct.

Chlorine bleach, and cleaners that contains sodium hypochlorite (chlorine bleach), are very harmful to wood, vegetation and aquatic life. Do not use chlorine bleach to clean anything outdoors.

STEP 2: Pressure washers are extremely harmful to wood surfaces and masonry that don't meet the severe weathering standard. High-pressure water streams readily erode the soft,

lighter-colored spring wood grain you see in lumber, leaving your wood deck looking like a 50-year-old fishing pier.

STEP 3: Consider using a powdered oxygen bleach that mixes with water to clean your deck or patio. Oxygen bleach mixes with water to create trillions of oxygen ions that deep clean mold, mildew, algae, and oxidized deck sealers. There are a number of products on the market that are available at hardware stores.

STEP 4: After mixing the powdered oxygen bleach with water and making sure it's dissolved, apply it liberally to the deck or patio with a hand-pump garden sprayer. It's best to apply it to a dry surface so the solution soaks in.

STEP 5: Work in the shade or early part of the day if possible to minimize evaporation. If the solution soaks in or starts to dry, add more solution. You want the surface to appear as if it's just been rained on. Allow solution to soak for at least 15 minutes.

STEP 6: After 15 minutes, use a scrub brush on a pole to agitate the surface of the wood or patio. The longer you allow the oxygen bleach to soak, the less you have to scrub. Work in small areas of about 50 square feet at a time. It's best to have a helper who is applying the oxygen bleach solution in advance of the person scrubbing.

STEP 7: Rinse the cleaned surface with plenty of clear water immediately after scrubbing. The oxygen bleach runoff will not harm plants. Allow the deck or patio to dry.

STEP 8: If you intend to apply a fresh coat of sealer, use a semitransparent one that's got medium color pigments and is made with synthetic resins.

Clear deck sealers will allow the wood to turn gray within months. Sealers that contain natural oils are food for mildew, mold and algae. Some of these have chemicals in them to slow the growth, but sunlight and water can remove these chemicals, allowing your deck to turn black or green in no time.

SUMMARY Realize that high-pressure water streams are very destructive. If the water stream is powerful enough to clean off mold, mildew, algae, etc., it's more than enough power to remove the wood fibers from the light-colored spring wood in your deck and dock.

Get Tim Carter's free weekly newsletter -- tool reviews, new product reviews, home-improvement tips and much more -- delivered via email. Go to askthebuilder.com to sign up.