Moldy Deck - Re-staining / Waterproofing Questions


Old 04-15-16, 10:14 PM
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Moldy Deck - Re-staining / Waterproofing Questions

Hey all,

I'm new to these forums, and am an intermediate skill level do-it-yourselfer.

I have a relatively new deck, but it's been getting moldy/covered in algae after every winter. Last year I scrubbed the deck so hard with a brush the stain came off in spots. It needs to be re-stained and waterproofed. I was considering using a deck cleaner and then removing the stain after but that seems like a waste a time.

First question is should I sand the old stain off (with belt sander) or use liquid stain stripper on it, taking off the mold/algae during this process. If liquid stripper is the option to do which stripper is the best?

Second question for re-staining is there a stain that is also waterproof or am I going to have to re-stain and waterproof/polyurethane etc after.

Just trying to get the deck looking brand new again and waterproofed for the rain/snow. Any help/tips/advice would be greatly appreciated!!

Thanks in advance for your help!

Last edited by movieguy2828; 04-16-16 at 12:14 AM.
Old 04-16-16, 04:35 AM
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Welcome to the forums!

The old stain doesn't always need to be removed in order to recoat but a lot depends on the stain that was used and what you intend to use. Pics could be helpful -

My SOP for cleaning a deck prior to staining is; wet the deck and spray a bleach/water solution on with a pump up garden sprayer, let set but not dry and then rinse with a pressure washer. I'll retreat and/or scrub any problem areas.

I generally mix the bleach/water 50/50 never stronger! Too strong of a bleach solution will destroy wood fibers Sometimes I'll add TSP to the mix, especially if the stain is degraded or there is grime other than mold/mildew. I rarely use commercially prepared deck cleaners or stain strippers. I like an old broom for scrubbing so my old worn back doesn't have to bend over A water hose can be used in place of a pressure washer.

All deck stains have waterproofing properties. Generally the better quality stains last longer than their cheaper counterpart. You never want to apply poly on a deck! The only sanding I do on a deck is on the handrail and/or to fix where someone got too aggressive with a pressure washer. No need for a belt sander. Nail heads will eat up sandpaper in short order.
Old 04-17-16, 10:40 AM
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I clean a deck just about like Mark does, except I don't own a pressure washer so I scrub the deck with a stiff brush after I spray on the bleach solution and then I rinse with the hose.

Deck stain is also sealer, the whole point of it is to waterproof your deck but some decks need it reapplied more often than others just like some products need to be reapplied more than others.
Old 04-17-16, 07:16 PM
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Thanks all for the tips!

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