Dealing With Moss, Mold, and Mildew

Spring is in full bloom throughout thePacific Northwest, but not everything green is in the garden. As the rains subside, we see green concrete everywhere – walkways, driveways, and patios. Looking closely at the house, we’re even likely to see the telltale sign of moss on the roof and mildew on our siding. This time of year, the most frequent request I get is to pressure wash something. But, thanks to modern chemistry, getting rid of moss, mildew, and slime molds isn’t nearly as tough a job as it once was and many times I don’t even need the pressure washer.

There are several really good products available at all the big box stores, department stores, and most hardware stores. In fact, Lilly-Miller introduced a new moss remover designed just for concrete last year. The product I’ve been using very successfully for several years is 30 Seconds Outdoor Cleaner and I guess I’m reluctant to change just because it is so darned effective. In many cases, all I need to do is spray it on the concrete or siding, agitate it with a stiff bristle brush, and rinse it off with a hose. And, it’s effective at killing slime molds and mildew as well as the moss. The same company has just released a new product which promises to be as effective, but with even less work. It’s called Spray & Walk Away. Mix the concentrate in a 5 to 1 ratio with water, spray it using a garden sprayer, and Mother Nature will wash away all the black and green yuk over time. This is also the only product I know of that will deal effectively with lichen. Best part of all, both of these products are manufactured right here in Troutdale, Oregon.

Occasionally, I do have to break out the pressure washer to deal with really tough jobs. It’s important to remember, though, that just washing moss, mold, and mildew from the surface is usually not enough. The “roots” are still embedded and remain alive in any porous surface like concrete or roofing materials. They will continue to grow and do damage, unless a chemical is used to kill them before using the pressure washer.

While the power of high pressure water can really speed up the cleaning process, it’s important to remember it can also do extensive damage very quickly. It will cut through vinyl and cedar siding along with composition roofing materials like a sharp knife. Be sure to use a wide enough tip angle (usually 25 or 40 degree) to disperse the water while still getting the surface clean.

As a final note, when it comes to removing the “green” of springtime, remember to always wear personal protective clothing and equipment. Read and follow all the warning labels on any chemicals and always wear close-toed shoes along with eye and hearing protection when using the pressure washer.


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