Cedar Roof Cleaning Seattle

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Cedar Roof Cleaning Seattle

Why cedar shakes turn grey

When wood is exposed to the effects of sunlight and moisture, its surface begins to change. This change is commonly called weathering. The initial change from reddish brown to silvery gray is the result of the ultraviolet rays from sun exposure.This usually happens within the first year of installation. Eventually the roof will take on a darker gray color. This indicates that your roof is being colonized by micro fungi. PWNG specializes in cedar shingle roof cleaning in Seattle

Should I oil my roof?

Originally your cedar shingle had only 3% of its weight as oil.[1] The effects of oiling a roof are temporary. UV rays break down the oils applied to cedar shakes in most instances within 3 years. Maintaining the oil on your roof should be a tri-yearly occurrence. The oils allow natural contraction and expansion that the cedar shake experiences, due to changes in weather such as:

  • Rain
  • Snow
  • UV exposure

These stresses to the wood cause micro-cracks. As an example, a butchers block , needs to be dried and should never be put away wet. When it is left out wet and the heat in the home is turned up or it is near a stove, it warps and cups like in the picture below. The warping is caused by:

  • Expansion
  • Contraction
  • Lack of Oil

Every butchers block made of wood, instructs the buyer on oiling with mineral oil.  The exact procedure should be applied to cedar shakes.

How to keep the appearance up

You can periodically clean your cedar roof in Seattle with a power washer. The top grey layer of exposed cedar is removed and you’re left with a fresh new layer. This should only be done for maintenance. On average ¼-3/16 inch of cedar is removed per cleaning. When deciding to apply stains and oils, keep in mind that, the sun will break down any coating or stain applied, eventually. In summary, cedars appearance if left outside in any sunlight: is grey. This is its natural color and there is no product on the market today, which can withstand 365 days of rain and sun a year.

Why you should very rarely power wash your roof

Losing 1/5 of your roofs life in one cleaning, should only be done in extreme circumstances .When excessive moss and fungi have been left untreated on your roofing, it is time to power wash. You should go in knowing that you are power washing to remove debris and moss that’s accumulated. Yes your roof will look great. This is only temporary though. There is no way short of trapping your entire roof off; to prevent the weathering caused by UV exposure. We are there to remove debris and moss and apply a moss control agent. This should be done at most once every 5-7 years.

Moss Control

Our process for cedar roof cleaning in Seattle is to use a safe organic compound known as Potassium Salts of Fatty Acids.[2]Mixed with some simple household detergent to make it stick, this chemical blend naturally kills all moss spores.

Periodic Maintenance

PWNG can’t stress enough that cedar shake roof restoration in Seattle is a maintenance issue .Applying our chemical blend once a year is fairly inexpensive, under $400 in most instances. The local average of replacing a shake roof is. between $350-550 a square [10×10 feet] .Budgeting this as a yearly maintenance cost is a lot less expensive then replacing your entire roof


[1] Oregon State University Extension Service (Publication EC1271)

[2] http://npic.orst.edu/factsheets/psfagen.pdf