We use a solution of about 30% cheap household bleach, a little orange detergent, and spray it on with a garden pump sprayer. You let the solution sit or, reapply. Most manufacturers recommend adding Jo Max.

You can broom the detergent, with bleach, with the grain of the decking and reapply for harder dirt.

We usually do this in early spring on an over cast day or in the evening as the sun is going down. It takes a while between the brooming and reapplying the solution.

After working the whole deck over for about an hour, or more depending on the size of the deck, you rinse with a heavy stream of a garden hose.

If you have wood, once every two years you should apply semi transparent stain.

The problem with pressure washing is it can raise the grain on wood. Some times pressure washing can expose the fibers of the synthetic. In any case the problem here is the black mildew.

You can bleach it out or use Hydrogen Peroxide.

It takes time for the bleaching to work so adding bleach to pressure washing does nothing for the mildew. After applying the bleach solution it takes at least thirty minutes to work.

Bleach dissipates pretty quickly and turns into a salt water. Thats why reapplying can be beneficial.

How’s the deck cleaning/renovation going this Spring? I agree. The composite decks are really paying for themselves pretty quickly.

Jaspar,

Pressure cleaning should be done according to the manufacturer’s recommendation. Unfortunately, for me, the suggestions are “light” in nature and just are not practical.

I used a 20 HP Honda 3500 PSI system on mine. The Xtendex held up very nicely. But again, it is up to the homeowner on how much is too much. I hope your deck turns out great. Send some pics when you are done.

Ardell,

I put copyright in there because I’ve run into a case or two where my photos’s miraculously showed up on other websites (blogs).

Deck rot has become a huge issue in inspections, particularly since the market turned. Cantilevered decks with rot should not be treated lightly, as the deck support runs into the home (1/3 out 2/3 in, is the normal ratio). Rot on the upper floor deck may mean rot traveling into the home’s floor joists on the second floor.

Second floor wood decks off the bedroom (that are not posted to the ground) are usually cantilevered off the master bedroom floor joists.

My wife and I plan to build a house with a Trex front porch, because Trex offers very durable white railings and deck materials.

Trex recommends “basic cleaning with a composite deck cleaner or a combination of soap, hot water, and a soft bristle brush at the time of installation, and semi-annually (typically Spring and Fall)”.

“Trex does not recommend the use of a pressure washer. The use of a pressure washer with a greater than 1,500 PSI and/or applied closer than 10″ from the deck surface could damage the decking surface and result in a loss of warranty coverage.”

http://www.trex.com/care/cleaningguide.aspx
http://www.trex.com/technicalinfo/mold.aspx
http://www.trex.com/technicalinfo/painting.aspx

They do cost significantly more at installation, but as you are pointing out, that is definitely made up in maintenance costs down the road. I put some composite decking in at my last house, and since I know the people that bought it, I stop by and see if from time to time. Some 6 years later it still looks good, and has had almost no maintenance done to it.

I always encourage my clients to go with the more durable composite decking over standard wood whenever possible. It may sting the pocketbook at first, but it well worth it down the road!