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remove stubborn mold from wood deck after power washing it

After power washing my deck,  there is green mold that remains in areas.  It is light in color but it is visible.  I power wash my deck once every year but only apply stain n waterproof it  approx every 3-4 yrs.  This is the first year  that mold was not removed by the power washer ... My question is , May I stain over the mold and if so what are the chances of it bleeding thru and being visible if any, or could you direct me on how and what to use to remove it before staining ?

 Thank You !

 Denise Dippery 
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Posted 2015-08-16T01:50:46+0000  by Nesi Nesi
The green stuff is probably algae not mold and there are any number of commercial products on the market to clean decks.  Another option is to just use ordinary bleach.  Mix a 3/4 of cup of ordinary household bleach in a gallon of water and add a teaspoon or two of laundry detergent.  The laundry detergent isn't so much for cleaning as it a surfactant, keeping things wet and moving around.  Keep the surface wet for at least ten minutes and have at it with a scrub brush on a stick.  Then rinse well.  I've heard you can also use oxygen bleach (e.g., OxyClean) but I can't tell you how much to use.

Chlorine beach will have an effect on the color of your deck, so you may have to stain again.
Posted 2015-08-16T09:33:18+0000  by Adam444
Absolutely do not stain over mold, Nesi!

Mold or mildew creates blooms as it grows and these nuisance growths with unseat your stain and discolor the surface.

You need to remove it completely before applying stain.

Behr All-In-One Wood Cleaner contains diluted oxalic acid.

Not only will it kill the mold and mildew, but it will remove the discoloration from the surface of your deck.

Apply a generous amount of this cleaner to the surface using either a pump sprayer or a scrub brush.

Allow the product to work for about ten-minutes and then thoroughly rinse with fresh water from a hose.

Apply another coat to stubborn areas and scrub with a stiff bristle brush.

Rinse thoroughly with a hose after ten-minutes.


The only mistake you can make with this product is allowing it to dry on your deck.

It is common for stubborn stains to require more than one treatment.

If the stains are deeply embedded, don't overlook sanding the surface to remove the discoloration before applying stain.
Posted 2015-12-01T22:10:17+0000  by Pat_HD_ATL
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