I built a completely pressure treated deck five years ago and stained with
Sikkens. It's on the north side of the house and now is very dirty---some
black spots (mold, I guess) on the rails, etc.
What's the best way to clean this without damaging the wood or stain (the
stain is holding up very well). I've been told pressure washing is too tough
and a no-no with pressure treated. TSP? Some of those deck
I washed mine with a strong clorox solution to get rid of the mold (I just
used a mop, and rinsed with a garden hose), and then re-stained it. The
clorox takes off the black stuff (mildew) quite well. However, it's a pain
to clean the railings (I imagine it's a pain with a pressure washer too).
The household bleach (1 cup in a gallon of warm water with a little
detergent or TSP added) will kill the mold. The detergent helps
spread the solution and loosen the dirt. It is easier to apply it
using a garden sprayer. If needed you could use a SOFT brush. Leave
the solution on for 5 minutes then rinse off. If the mold has been on
there for some time, a second cleaning may be needed.
I didn't want chemicals slopping over the plants under my deck, and there
was too much area to put drop cloths, (besides, it would take forever to
scrub 1500sf)so I used an electric pressure washer.
Okay, there were a few bits of minor damage, but overall it worked well. I
think the damaged areas probably needed to be cleaned out anyhow.
I first checked a number of Stain Mfg's sites; some say no pressure washers,
others say none over 1300psi.
north exposure, you probably have alot of mold, your stain may look good
but you need to restain after you clean, If you dilute your bleach much
you may have to redo it. I am in full shade and bleach full strength on
wood and concrete. Power wash will not hurt wood, use a wider tip
I called Zinsser about Jomax. They do not recommend it for unpainted
surfaces or where the finish is worn through. They recommended Wolman
instead. Wolman is another Zinsser label. See www.Wolman.com. I believe the
difference is oxalic acid. I have used neither product.
I've pressure washed PT wood decks with no trouble. Rather than buy
deckwash, I mix my own combo of 2 scoops laundry detergent in a 5 gallon
bucket with about 1/2 a bottle of bleach. Spray it on softly and let it
soak 15 mins, then blast if off board by board. It looks brand new. And
yes, let it dry thoroughly before sealing.
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