Preventing Mold and Mildew on the Outside of a House

Spraying mold and mildew remover on the outside of a green house.
Spraying Wet & Forget mold and mildew remover on a house.

If you live in a warm, humid climate, mold and mildew will often form on the exterior siding and trim of your home. It’s important to clean the outside of your house regularly to remove any mold or mildew and to clean it thoroughly before painting.

Make sure the paint you use on the outside of your home contains a mildewcide. If it doesn’t, have a mildewcide additive added to the paint at the home center or paint store.

If the mold and mildew return, apply an outdoor mold remover, like Wet & Forget, to your siding and trim to keep the outside of your house mold and mildew free for up to one year.

Watch this video to find out more.

Further Information

Danny Lipford: When a house has just been painted, people want to keep that new finished look, so they often ask how to keep the mold and mildew away. It really starts before you paint.

The mold and mildew have to be cleared away before new paint is applied. Then the paint itself should contain a mildewcide. Many brands make it part of their formula, or it can be mixed in as an additive at the paint counter.

Even with these precautions, the mold and mildew will eventually return. At the first sign of new growth, apply a mold remover, like the one from Wet & Forget. It’s non-caustic, non-acidic, and contains no bleach, so it won’t damage your new paint.

You simply apply it to a dry surface and let it go to work. No scrubbing, rinsing, or pressure washing necessary. It works with the rain and the wind to gently remove mold, mildew, and algae over time.

And while the cleaning is gentle, it’s also thorough, so it lasts up to a year or more. Then simply reapply it to keep your house looking like you just painted it.


  1. Danny, et. al:

    How would I remove a streak of mold from stucco ?


    Great info on site and radio –

  2. Hello. I will like to know if you can help us. My son purchased a home in Houston and we are having a pretty bad time since everthing is falling apart. One of the biggest issue is that water is zipping in the concrete floor slab. I fixed the brick outside from top to bottom and water stopped for a little while…then again we found the slab wet.
    In one of the bedrooms i cleaned the entire slab by had, removed the paint and dirt…applied the sealer for concrete but the problem still there and most of all white powder and the smell.
    We also have some mold on the vents of the air conditioning and those need to be changed. I have a quote for 1500 and that is pretty high for our current income which is very very tight.
    Where do i find out how to remove and change the ducts of the air conditioning on the attic. .. a step by step will help since we are planing to do that.
    Second any thoughts in the water issue…how do we stopped.
    The house has brick all around and there are the “holes” for water getting out but I suspect that is the problem.
    We need to remove the sheetrock and change the insulation…
    any ideas in how to waterproof the interior of the walls before putting the new insulation and sheetrock.
    We live in Houston where is very humid and hot plus rains a lot…plus we do not have air conditioning due to the mold on the ducts…
    Please help me and my son to figure out how to conquer the house. We are originally from Sacramento and we do not have too much experience dealing with Houston’s weather.
    Thank you so much.
    I appreciate you and your work.

  3. To the homeowner with the water and mold problems.

    You need to find an honest contractor to diagnose your problems. What you wrote just does not fit any facts I have ever heard of. By water “zipping” I assume there is water on the surface of the slab. This water is flowing from somewhere and no amount of waterproofing of walls will stop it. Make sure the ground outside is well below the level of the floor inside the house, then make sure that water does not accumulate around the house when it rains. Besides the obvious question of drainage, thare too many undefined factors to consider before anyone could give you reliable advice.

    Did this house actually flood in one of Houston’s recent flooding events? If so, the flooded sheetrock and insulation will have to go, and new sheetrock and insulation nstalled.

  4. I have streaks of black on my stuco. Do you think painting it with the rhino shield paint will stop the black streaks? Please reply I need help

  5. I’m about to make an offer on a house with vinyl siding- the siding is covered with mildew, yet none of the nearby vinyl siding houses seem to have the same problem. Could there be something wrong with this siding, perhaps a problem under the siding.?


    Charlie B

  6. Black moldy substance on outside of house behind A/C and at crawl space entrance, with no gutters I’m thinking about buying. Natural wood siding. Would installing gutters remedy this?

  7. The Mildew is usually from lack of direct sunlight. It will always come back even if you power wash it. It will be there the following year. I do recommend getting a cheap power washer as they work well enough to get it off. It comes off easily with the power washer:)

  8. The partly stuccoed outside chimney has what was described as water stains (from the chimney?) and dirty, perhaps mold. What can be done to do whatever is necessary to bring the chimney back to its original condition

  9. I have a recurring mold/mildew issue on the siding on the north side of my house. It gets zero sunlight so I pressure wash every year and it returns. Was wondering if I could provide artificial sunlight to that side of my house to prevent it from coming back. Would installing exterior lighting set to shine on that side of my house replace the benefits of the sun in preventing mold/mildew growth? If so, is there as special type of bulb (UV, IR)?

  10. Hello. I live in Virginia and have a pine wood siding house, and I have a time with it for 19 yrs. I have stained with all kinds of stains and have literally sanded the whole house down twice with a palm sander. The reason of stripping it down is it keeps getting this little black freckels starting on it and it ends up spreading across the whole entire board on top of the stain. What I don’t understand is I’m on top of a hill,wind constantly blows, no trees, even gets on the boards that are under the porch where no water gets to it. Is it mold ??? Or what? Thank you!

  11. I am a painter by trade, so I know how to properly prep a house for painting. But I am stumped! My house is moldy on the south and east sides, where it has sun all day. It’s pine clapboard and was grounded to new wood, painted during a dry spell, optimum temperature, using Ben Moore exterior paint. What gives?


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