How to Prevent Mold on a Deck 4.6/5 (14)

by Deck Stain Help

Updated February 2020

Preventing Mildew on a Deck

Mold growth is a common problem that can arise during the deck staining process. Today we talk about what causes your deck to turn black from mold and how to prevent it. If you have encountered mold during your deck staining project, we want to hear from you. Feel free to leave a comment below with pictures of your deck stain projects.


How to Prevent Mold on a Deck from returning.

One of the biggest enemies of a deck is mildew and mold. With moisture being ever so present outdoors, the mold is bound to find its way onto your deck. Typically, mold will begin to appear on the more shaded sides of a deck. Anywhere there is less sun means there is more moisture present making conditions ideal for mold growth.

Once mold infiltrates a surface it only continues to spread if conditions are favorable. Mold can get under wood stains and sealers and cause them to fail prematurely. Mold will also rot and decay wood if it is neglected and jeopardize the integrity of the deck and decrease its longevity.

To remove mold from a deck, clean the surface with a deck cleaner containing sodium percarbonate or a mix of bleach and water. We are not fans of bleach on wood but sometimes this is best to help get rid of the mold. If you use bleach, mix at a ratio of 1 part bleach to 5 parts water.  Use a stiff brush or pressure washer to clean away the mold, dirt, grime, and graying. After cleaning a wood deck, the surface should be recoated with a protective deck stain. Composite decks can also be protected with the proper sealer.

To prevent mold from reoccurring you can use a product called Wet and Forget. This product can prevent mold, mildew, lichen, and algae from appearing. For maintenance even if mold is not present, spray Wet and Forget onto the deck’s surface and let it do the work for you. No scrubbing, rinsing, or pressure washing involved. This is a non-caustic product that contains no bleach or acidic material. It can be used on almost any type of wood or composite decking.

Apply Wet and Forget to your deck surfaces every 6-12 months as a mold preventative. Even if no mold is present, Wet and Forget will kill and prevent unseen mold spores from growing. It is safe to spray on top of most wood stains and sealers. Wind and rain will continue working with the Wet and Forget product overtime to keep mold away. Use as needed to prevent mold on a deck and to keep all your exterior wood surfaces clean and mold free.

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Mike
Mike

Can I use Wet and Forget on cedar deck before standing.

Mike
Mike

I ment staining. Had mold in or under new stain.Striped and sanded.still small amount left.

Terry
Terry

Very informative website! I have a cedar deck in great shape but time for it’s restaining this summer here in suburb of Chicago. I use a brand called Rymar Extreme Westher semi transparent wood sealer stain from Wisconsin.
Question:
Can I use the Wet n Forget this August to let it work over the fall/winter season and then power wash lightly/re stain next year 2020?

Bonnie
Bonnie

Can we use sealer over wet and forget on a deck?

Mark
Mark

Should I put a layer of Poly on the deck after I put on the Stain

JIm Leonard
JIm Leonard

I built a new redwood deck last year and sealed it with transparent cedar from Armstrong Clark. Over the winter the entire deck was over run with mold (north facing deck with very little sun in the winter). I just pressure washed the entire deck with water only and it removed all of the visible mold. What should I do now before repeating the staining process? Is there any stain that prevents mold over the wet winter months?

Sandy
Sandy

We have a five month old deck that is showing signs of mold. We used the treated pine and were told to wait a year before treating. I’m concerned as we have a lot of money invested. Just not sure what to do we have had so many different opinions.

Christine Lux
Christine Lux

We have a covered front porch that we started refinishing a year ago, but we only got half way finished, so we covered it up to prevent it from getting wet (while well covered rain does blow in when it’s windy). The wood is maple, and just like a wooden floor inside the house. We just lifted the cover off, ready to complete the job, and discover some signs of black mold in between the floor boards in a few places, as our covering job was not completely successful. The wood, though, is still structurally sound. We thought we would give it a sanding with our hand-held belt sander, then seal and varnish it as we did the other side. That way we will address the cause of the mold. Do you think that will be enough? We are hesitant to apply anything else, as we already have to blend it in with the finished side. I don’t want anything that would bleach it, because it gets sun and it would continue to bleach, and then we would have spots where it is lighter than the rest of the floor. (we already have a problem, because we used a product on part of the floor that we couldn’t get all out. It was a treatment that we layed down then covered with paper. By DuPont. We used the remover and sanded it down several times with professional sander, but could not remove it, so if you have any ideas about that, that would be an extra bonus)

Sheila
Sheila

After the winter snow disappeared our cedar deck which we have left natural has a greyish film on it. It reminds me of a wet tissue that has dried in the sun. Is this Mold or mildew? We have wet it and swept it but it remains in difficult areas. Can you explain what happened and is there something we need to do in the future?

Robert
Robert

Pressure wash it with a bleach free deck leaner then use a clear wood sealer on it. Ask at a ‘good’ diy store that knows about it.

Marybeth
Marybeth

We made the mistake of hiring an inexperienced person who pressure washed our 6 month old deck and started staining the next day. This was 3 years ago. We have had constant black mold issues on our deck. It does face the east and some woods, so only gets the am sun. We have had it professionally pressure washed twice and restrained twice. We started using wet and forget and it has helped, but lots of mold in places. My husband is ready to tear it down and pay for composit. I cannot believe there is not a product out there that is capable of sealing wood? Any suggestions are welcome!

Gmacin
Gmacin

Our deck is on the North side, so in the shade almost all day plus our dryer vent is directly under it. Thus we have lots of green mold growing on it. Will the Wet and Forget work on this?

berin
berin

Wet and forget..

Vee
Vee

Do not use bleach on any cellulose material with mold infestation. It causes a reaction with the mold, releasing mycotoxins into the air. This can make a person VERY ill, especially if they are part of the 25% of the population that has no natural protection against mold toxicity.
Instead, use a combination of washing soda (soda ash) and real TSP (trisodium phosphate) in water. Spray with a garden sprayer, let it set for a few minutes, and hose off. Scrub with a brush if the mold is deep. In the case of mold remediation in a basement or home, you would leave it on (no rinse) and let it dry. This kills the mold and it will not return.

Judy
Judy

What is the best protective deck sealer. We get Moldova every summer.

Josh
Josh

Does it prevent mold permanently?

And does that mean once you use wet and forget you never have to re-Stain your wood deck again?

wanda Mangus
wanda Mangus

Our deck is 1 foot above a carport with a metal roof. What do you recommend I use without damaging metal roof?

ron
ron

serching for composite deck sealer,need help