Home>Discussions>EXTERIORS>Newly stained composite siding, some spots with black mildew!?
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Newly stained composite siding, some spots with black mildew!?

I just spent a lot of money to have my house re-stained and there are certain spots of my house where mildew is showing on top of the stain?  How is this possible, how can it be corrected?



Re: Newly stained composite siding, some spots with black...


The reality is that if the conditins are right, i.e. cooldamp, little sun, mildew will return. Most quality stains and paints already have a mildeciode in them. There are mildecides that also can be added. How effective they are, I am not sure, but they can't hurt.

The most important thing is to kill the existing mildew before application of the new paint/stain. Hopefully your contractor did so. During my contracting days, the whole house got routinely washed down with bleach and detergent and then thoroughly rinsed.

A house can be washed to remove new mildew, but it is more involved to avoid causing streaking or discoloration. Generally, wet the siding down first, then  spray the siding starting with the bleach/detergent mixtre starting from the ground and working ujpwrds. Keep the siding wet with the solution for about 5 minutes and then rinse from the top down. To avoid damaging landscaping, rinse down the plants thoroughly before starting, and then when finished with the bleaching. What bleach goes into the ground does not hurt the plants, it is what gets on the leaves and is allowed to dry there!

There are a couple products that inhibit mildew return, "Wet and Forget" and "Concrobium" are two that come to mind. these are spraed on and allowed to dry on the durface, leaving a residue that inhibits re-growth of mildew. Both can be used right over the mildew and will eventually cause it to disappear. Of course, you can do a bleach pre-wash to get rid of the black staining sooner.

Re: Newly stained composite siding, some spots with black...

Thanks for the help!

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