Seattle Sun Newspaper - Vol. 8, Issue 6, June 2004

Copyright 2004 Seattle Sun. Please feel free to use the article below in your research. Be sure to cite the Seattle Sun as your source.

AROUND THE HOME:

Beware of roof cleaners with pressure washers

By MATT MAURY

About this time each summer we begin to see folks attempting to clean their roofs with pressure washers. After all, when you put together a mild winter, a lot of rain, some of shady trees, and any old roof, there is an excellent breeding ground for moss. And, there is little worse for a roof than leaving moss unchecked.

Yet taking the wrong actions can create new problems leaks!

Perhaps you've noticed that, at this time of year, there is an outbreak of people with pressure washers offering to clean moss and debris off roofs. Of course, anybody can rent or buy a washer, with no training required to operate it, then, print up a few business cards and be in the roof cleaning business. Generally, these cleaners are long gone by the time the leaks occur in the rains of the following winter.

So, what's a homeowner to do about the moss, tree needles and debris?

First, a person should understand the structure of a roof. It is made up of three elements: sheathing (the wooden base); felt (the water-resistant paper), and the visible roofing material wood, asphalt composition, tile, slate, metal.

The exposed part of the roof is punished by the elements throughout the year. After the winter rain and snow, there is the baking in the summer sun.

These cycles of weather, year after year, lead to a breakdown of the structural components of the roofing, particularly in wooden & asphalt composition shingle and wooden shake roofs.

These weak areas, especially at the edges of individual shakes and shingles, are where moss starts to grow. Then, when high power pressure washing is done, the already weaken areas are further damaged by the pricking jet of water.

Often when the water is aimed directly at the roof, at a 90-degree angle, the roofing material is punctured, as is the underlying layer of felt.

When skip sheathing (alternating boards and open spaces) is the base layer of the roof, which is usually the case under wooden roofs so they can "breathe," this can create a small holes through the roof, which will leak directly into the attic during the next heavy rain..

Armed with information about the age and make-up of a home's roof, the homeowner can make effectively evaluate the options available for controlling the moss:

· Option A: Spray Moss Killer on the Roof. Many of the firms that perform seasonal tree and shrub spraying also offer sprays of moss killer that are effective, as well as done in a manner to not harm any surrounding vegetation. The dead moss will eventually blow away.

· Option B: Follow-up Option A with sweeping or air blowing the dead moss off the roof. While the spray service will not do this, there are a few companies that specialize in this method of moss removal.

· Option C: Pressure wash the roof. Because this is an effective, efficient way to clean decks, patios and driveways, people assume that is a good way to clean roofs. It should be done only at a very low pressure setting and only at an angle of not more than 30 degrees above the roof's plain. This will minimize the potential damage to the roof. Before doing this, check to make sure that it will not void your roofing material's warranty.

· Option D: Do nothing. When the roof is older, especially over 20 years, it might be wiser to do nothing, wait until leaks develop, and then put on a new roof. Often on an older roof, more damage will be done by walking on it than will be done by allowing the moss to continue to grow.

If this is going to be a summer project this year, consider these things also. If you know the manufacturer of your roofing material, consult that company for advice. When hiring someone to do any work, make sure the person or firm has a business license and liability insurance. If the firm does roof repairs, it should have a contractor's license. It is always preferable to hire people who have been in business for at least two years. If there is a problem, there is a better chance that they will be around to help solve it.

And, for any homeowner venturing onto the roof, be careful! It's slippery up there!

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Matt Maury is president of the Home Owners Club of Seattle. His column is intended to help homeowners better understand the complexities of owning and maintaining their residences.

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