Yes especially with cedar. You might try this first.

I use a heavy duty scrub brush with a long handle, similar but smaller than
a push broom. Mix half a cup of dish washer detergent and a 2 cups of
bleach into a bucket of water. Spread over the deck, wait 15-20 minutes
then rinse/brush off.


"Scott" wrote in message
...
We have a large cedar deck that's two years old. The clear stain only
lasted
a year and a half before greying. This spring, I want to have the deck
power-
washed, and then I'll stain it with a Sikkens stain with some pigment. My
wife has a Polish friend who owns a power washer. He says he'll clean it
for
free. The contractor who built the deck said you have to be careful when
power-
washing. If you use too much pressure, you'll lift the grain of the wood
and
damage it. That's why I'm planning to ask a professional to do it. Is
there
a danger to asking an amateur to do it instead?

Thanks!
Scott