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What is the mysterious green substance on my deck, what is causing it, and how can I remove it?

Asked by Deniz Kılıççı
5 months ago
Last Updated: June 13, 2024

What’s up with this green stuff on my deck? Do you know what causes it and how I can clean it off?

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محمد مرادی

Bleach can be used to get rid of fungus.

Violeta Adamović

Each year, spray bleach on the deck, pressure wash it, and then seal it. This area is likely the north side of the house, so get into the habit of doing this regularly!

Liana da Paz

To get rid of mildew, pressure wash it away and do this every year. You can also apply a bleach solution to prevent it from coming back. Be careful not to spray the bleach onto plants as it will kill them.

آوین جعفری

I accidentally spilled bleach on my deck and now it doesn’t absorb stain properly. There is a special type of wood cleaner that can help without causing streaks.

Nicolas Addy

Sure thing! Here’s the rephrased text in a conversational tone: , right?

Gladys Holt

That green stuff on your deck? A bleach mixture can take care of it, just be careful not to make it too potent or you might notice some color changes on the wood.

Gladys Holt

‘t use a pressure washer on the wood. It can cause discoloration and damage if not used properly, and then you’ll have to refinish the whole deck to fix it.

Alexsandra Costa

You can find a spray called “mold and mildew release” at Home Depot.

Gladys Holt

I’m not sure about that, I’ve never personally given it a try.

Terrance Wheeler

Use an outdoor cleaner along with a pressure washer

Emilie Madsen

It seems like someone celebrated St. Patrick’s day a bit too enthusiastically on your deck after drinking green beer.

Andrés Pastor

Looks like there’s algae on your deck, maybe consider giving it a power wash.

Darsh Babu

Try using Ez House Wash – simply attach it to your hose and give everything a good rinse. It’s great for mildew.

Onur Köylüoğlu

Oxiclean does the job just like bleach but without the strong chemical odor.

Rasmus Maki

When dealing with dirt, a power washer is the way to go.

Sienna Evans

To address the moisture issue, start by pressure washing the deck and letting it dry completely before applying a coat of stain. It’s important to seal the wood to prevent further absorption of moisture.

Alyssia Charles

Check the cleaning solutions label. If it contains sodium hypochlorite, it’s basically just bleach but priced higher.

Sara Murto

‘s Tri sodium phosphate is even more effective and can be found at Lowe’s, Home Depot, Menards, or any paint store. Be sure to follow the instructions carefully to avoid harming plants and risking burns! It surpasses bleach in performance

Nadia Khalil

Is also effective when used in the washing machine to launder clothes

Sara Murto

No way that paint is coming off, haha

Adele Brandvik

Dang, I could really use a Soylent Green gif right about now.

Mason Roy
Sara Murto

If you’re dealing with mildew, most deck washes can help keep it under control. Tri-sodium phosphate is especially effective. Make sure to wash the entire deck, including the underside, before staining if you want to add color and seal it. Keep in mind that if you use Thompson’s Water Seal, this will need to be done annually.

Arnold Ross

The wood is soaking up water and expanding due to the presence of algae. To fix this, try using wet and forget, then rinse with a hose, allow it to air dry, and finally apply a coat of stain.

Benita Börner

Mildew growth

Michael Collins

Just spray some bleach on it. By the next day, it should be dead and turn black. Then just pressure wash it away.

Fábia Castro

Just plain algae… bleach can get rid of it. Then, just rinse it off with water.

Aada Lehtonen

You should use a power wash.

Aditya Hiremath

To get rid of moss or fungi, a power wash will do the trick.

Akash Singh

Power wash to eliminate mold.

Gertrude Austin

Definitely not mold, that’s for sure.

Mikel Daniels

Is definitely not mold. 🫠

Akash Singh

I think it’s due to the moisture not being able to dry properly. Personally, I’d go with power washing.

Jessika Tollenaar

Reminds me of algae, not mold

Jessika Tollenaar

It seems like algae, people find it on the sides of their house. Just Power wash it off or use DAWN and warm water to scrub it away

Jessika Tollenaar

Not looking to argue haha but mold and algae are different – one is a fungus and the other is a micro plant. Either way, I’m not trying to be rude so apologies if it came across that way.

Fátima Vázquez

Hey, you’ve got it all mixed up! If you’ve got oak trees or maples in your area, that’s POLLEN! It’s green and can be easily washed off if you act quickly. I used to face the same problem every year back where I used to live because of those specific trees.

Samuel Burton

As light as it is, you could probably spray it with any bathroom cleaner and then rinse it off. I don’t think you need to resort to pressure washing just yet.

Rose Lowe

Nope, not mold. Just some tree pollen.

Sophia Campbell

Looks like algae or moss. It tends to appear in damp areas on the less sunny side. You can try a light wash with Dawn dish soap and a rag or gently pressure wash with a brush.

Julia Duran

Seems to be pollen. Just give it a few weeks and then use a pressure washer to clean it off.

Matt Lawrence

The water is just dripping off the railings… The wood is wet, just hose it down and apply some oil to protect it

Gertrude Austin

Deck cleaners can be used. Apply some of the solution and then use a stiff-bristle brush to scrub. Make sure to do a spot check first to avoid changing the color of your deck.

Wera Höller

Spray the area with bleach using a spray bottle. Watch it vanish before you even reach the steps back into your house.

Mikel Daniels

Notes that bleach can cause discoloration on wood, making it unsuitable for use unless you plan on painting over it.

Wera Höller

You missed the mark, Amy.

Ludmila Lamprecht

Using diluted bleach effectively targets problem areas by penetrating deeply. It’s essential to address issues like lack of sunlight and ventilation properly to prevent recurrence. Proper maintenance is key to preserving the longevity of your decks. I have decades-old decks and tables that still look great thanks to my expertise in this area. Unlike Thompson deck stain, which only provides temporary results akin to applying Pledge wax, my method ensures long-lasting protection against grime and mildew.

Ludmila Lamprecht

Bleach, when used correctly, washed off, dried, and applied correctly with a good product, will not damage or change the color of anything! Failure to maintain it properly will result in all of those issues. Mold and decaying leaves, pine cones, branches, grease from grills, bird droppings, and dog waste will also not look appealing… Always maintain it, or you will need to replace it frequently…

Cody Kennedy

Why don’t you work for Haarp and try to stop the rain

Terry Woods

I’m not sure, maybe those weeds over there

Olive Cooper

Seaweed

Volkan Korol

Boogers are simply a fact of life

Charles Dupuis

To get rid of mold or moss, simply use a stiff brush and cleaner. There are many cleaners available, you can use one of those or something you have at home.

Eleanor Cooper

No need to argue. There are plenty of products available to fix this issue. It’s a common problem for everyone.

Lucy Salamonsen

Avoid power washing your deck at all costs. This can harm the surface, creating pockets that trap water and dirt. Instead, opt for a deck cleaner and a garden hose to tackle algae buildup.

Alla Ohrimovich

Hey Charlie! Knowing how to properly power wash a deck can really give it a fresh new look. That green stuff you see is actually moss, as algae typically only grows underwater. And if you don’t believe me, feel free to look it up! Avoid using bleach on decks, as it can be corrosive and end up damaging the wood fibers.

Ludmila Lamprecht

Oh, moss, mold, and mildew. Just spray some diluted bleach on it. Let it sit for a couple of days. Then seal it with Australian Timber Oil stain. Repeat every few years. If you skip that, your deck will turn black, green, and super slippery like an ice rink all year long!

Olivia Mills

To start, steer clear of bleach. Mix one part blue ultra dawn with two parts water. This solution will effectively eliminate algae without causing damage to your deck or nearby plants. It’s also handy for getting rid of moss on lawns without harming the grass.

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