Keeping Mold from Growing on House Siding?

April 20, 2009

Mold from Growing on House SidingEvery year we have to power wash the siding on the north side of our home. We get a green/black mold that comes back every year. Is there anything that will stop this? The problem isn't getting it off the house, the problem is that it comes back every year.


By Kath from CT


April 20, 20090 found this helpful

Hi Kath,

I searched the EPA website and couldn't find anything that specifically talked about mold on siding, but they do have a page where you can ask questions. Might be worth a try:

Good luck!

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Bronze Post Medal for All Time! 213 Posts
April 20, 20091 found this helpful

You can buy this at Home Depot, you won't be disapointed! You put it in a garden sprayer & spray it on once a year... then each time it rains, it binds with the rain to work. It's not harsh or bad for the enviorment. It's $40 for enought to cover 1000 feet. You dilute it 5 to 1.


Product info:

Here's what they say:
Our revolutionary patent-pending, "No Rinse" concentrated cleaner that removes green and black algae, mildew, fungus, and lichen stains from roofs, siding, decks, brick, stucco, and other exterior surfaces. Spray & Forget is an eco-friendly, biodegradable, non-corrosive product that does not require damaging power washing and/or brushing techniques. In fact, no rinsing is required and your landscaping will not be compromised. Also an excellent preventative.

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Bronze Feedback Medal for All Time! 147 Feedbacks
April 20, 20090 found this helpful

I had this problem. I sprayed it with bleach in a spray bottle every week till it stopped coming back,good luck.

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April 25, 20090 found this helpful

Drive around and you'll notice that happens with most buildings' north sides. Especially those that don't seem to have several hundred feet between them and the next building or fence. I've heard that out in the forest, that's how you can tell which way is north - by the fungus that grows on the north side of the trees.


I'm glad to hear about the No-Rinse. I'm going to check it out for our garage.

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April 25, 20090 found this helpful

The north side of any structure whether out in the forest or at home gets the mold, mildew and moss. The north side of anything gets the least amount of sunlight. I don't think you can prevent this as it's the sun that kills and prevents it from growing in the first place. Noella is right, that mold and mildew tells you where north is.

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April 16, 20170 found this helpful

Use amonia and water

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July 13, 20170 found this helpful

Using a anti fungal soap when cleaning the house will help with the mold growing back each year the problem with most anti fungal soaps is that they are harmful to plants so I need to be really careful when using the soap now the mold will still grow back but is will decrease the speed of the growth of the mold

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2 More Questions

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March 7, 2006

My house has some green and black mildew on the brick and siding. The house does not need painting. I am thinking of having it power washed to remove the mildew. What time of year should it be done? I live in the Southeast.

Iris from Columbia SC


By (Guest Post)
March 8, 20060 found this helpful

we have white vinyl siding on our house and we get the green mold on ours too. what we do is every spring we spray it down with clorox. My hubby uses a sprayer that you pump by hand...I think it is also used for spraying plants and trees. anyway it works great. no need to rinse or scrub or anything. We were going to get ours powerwashed , but then we heard that is could put holes in the siding if the person doing it didn't do it just right, so we just spray it every year now with the clorox. hth.



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By Carol (Guest Post)
March 9, 20060 found this helpful

I, personally, dont think power washing is all its cracked up to be... It forces water under the siding of your house or deck. (Dont forget water and wood dont mix...) The water goes in all the little invisible cracks. Also, for mold or mildew you need to use chlorine bleach... let it set and then rinse... Are you sure the green isnt moss? I have moss growing on my roof.. Moss and mildew can come together.. imho because each thrives in a wet or damp environment.. BTW, look into removing any trees, bushes, or plants that cover your house and prevent the sun from shining on the places where the mildew is growning... Best of luck...

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July 19, 20080 found this helpful

I lived in Louisiana for about 20 years. I had my house pressure washed every year or two. It thoroughly took off any mold or dirt. The house was brick with exposed wood & trim & soffits. Any areas that didn't get direct sun, often got a little mold. The pressure washing also extended the life of the paint. I researched paint & bought the Valspar product made for the South with a mildew inhibitor in it.


My paint lasted for about 16 years before it showed signs of needing to be redone in a year or two. The washer also did the carport floor & driveway. The brick house looked great after the washing & was worth the $70.00-$100.00 that it cost (last time I had it done in LA was pre-Katrina).

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By Guest (Guest Post)
August 20, 20080 found this helpful

I have used successfully a product called "INSTAGONE".
Spray on and watch stains disappear and wash off. It worked for me.

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May 12, 20160 found this helpful

yes, I am very concerned about water getting under the vinyl siding between the wood and siding. BAD! I have mold (not moss, I don't think) Peak of house is VERY high (built on a hill) Agree we power washing.


Sure would be labor intensive to climb up a ladder and do by hand. but maybe only way.

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September 5, 2014

Can I use sugarsoap on outside walls to clean green mildew off the house wall?

By Julie from New Zealand

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