The mildew and algae on this vinyl siding can be removed quickly with a solution of oxygen bleach. (Tim Carter / May 24, 2013)

DEAR TIM: My primary home and a camp I own in the woods both are covered with siding. One is wood, the other is vinyl siding, and both are dirty. In the past few years, I've been stunned to discover mildew and algae growing on the vinyl siding. I thought vinyl siding was supposed to be maintenance-free; that's why I purchased it. What's going on? Should I just drag out my pressure washer and get to work, or is there an alternative method to clean siding on houses? --Patrick O., Fryeburg, Maine

DEAR PATRICK: Each week I receive emails from homeowners just like you. They share your astonishment about having to clean their vinyl siding. Many homeowners are not too happy, as the salesmen's claims about no maintenance seem to be as hollow as an old log.

I've seen hundreds of printed ads and heard countless radio commercials with these maintenance-free statements when it comes to decking, siding, railings, fencing and so forth. As you now know, it's just not true. Certain products do require reduced maintenance, but none are maintenance free.

You're probably wondering how mildew and algae can survive on plastic or vinyl siding. The mildew and algae are feeding on sugars, dust, dirt or other things that are attached to the siding. Many people are unaware that trees, both evergreen and deciduous, often broadcast ultrafine aerosols of sugars at different times of years. Park your car under certain trees and you'll discover thousands of tiny droplets of sap or sugar on the painted finish and glass. This is yummy food for mildew and algae!

When it comes to wood siding, the mildew and algae are possibly feasting on the actual stains and sealers you may have used to preserve the wood. Many clear and semitransparent wood sealers and stains are made with alkyd or oil resins. These natural oils are also delicious food for mildew and algae. Some of the sealers and stains contain chemicals designed to prevent mildew and algae growth, but these chemicals can break down when exposed to sunlight and repeated exposure to rainwater.

I know that you may love your pressure washer because it's a cool tool, but it can wreak havoc with houses if used improperly. As with Spider-Man, so it is with pressure washers: With great power comes great responsibility.

The water that's ejected from the tip of the pressure washer wand can be driven into cracks and crevices where water is not supposed to go. The intense water stream can and will erode the lighter-colored spring wood in your wood siding, causing it to look older than it actually is.







