Just another small sign of Natures' ongoing attempt to reclaim our humble abodes and adapt them to her needs.  This naturally occurring fungi finds the damp shady areas of the house, under eaves and gutters, along the bottom edges of clapboards and shaded gables. It appears as black, gray or greenish dirt spreading out from it's concentration in the crevices and horizontal corners of the house.

The good news is that mildew is easily removed with a solution of household chlorine bleach and water. Mix about a cup of bleach to a gallon of water. A stronger solution may be needed for stubborn areas. A garden sprayer works great to apply the solution. Spray the solution from the bottom up to avoid streaking. Scrubbing should not be required, the mildew should just disappear back into Nature. After the mildew is gone rinse the area with a water hose.

The short answer is not much, but there are some measures that you can take to retard and delay mildew's reoccurrence.

Do not use oil (Alkyd) based paints or stains on the exterior of your house. The oil base is food for mildew. Acrylic exterior paint or stain is a better choice.

Have additional mildew retardant added to the paint before application. Most exterior paints have a fungicide ingredient, however, you can request that additional fungicide be added at the paint store ( for an additional fee of course).

What is mildew
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Simple Control Maintenance 
Keep the exterior paint clean. A good power washing
every few years is a good idea. Remember that if mildew is allowed to remain for extended periods it will begin to erode the paint film and cause premature failure of the paint. It can also present health risks for those with respiratory sensitivity.

Simple control maintenance will help keep your house looking great and less inviting for hungry fungi.
Do not mix chlorine bleach with anything but water and NEVER mix bleach with ammonia. Always use common sense and caution when using, mixing or spraying chlorine bleach.

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