Washing and Cleaning Cedar Roofs

Washing or cleaning cedar roofs is probably the most controversial aspect of maintaining cedar roofs.

Power washing can cause serious damage to cedar roofs

when done incorrectly.

Over time cedar roofs go dark. It is a natural process. Cedar roofs may also become covered in moss and lichens.

What is actually happening to your roof?
How does cleaning the roof prove value?

Cedar roofs go dark primarily due to a collection of dirt that gathers from interacting with the environment. When it is raining out the roofs get wet. The moisture sits in the pores of the wood. The wind gathers dirt from the ground, from vehicles travelling by and other sources and blows it onto the roof. Over time the roof becomes dark as the dirt builds.

What does dirt (soil) and water make? Add the occasional bit of sunshine and you have a garden.

In the soil that lands on the cedar roof, there are seeds and spores that eventually germinate. The roof now has its own private supply of moss and lichen, even sometimes trees.

Powerwashing or cleaning the roof with mildly pressurized water is the best way to clean moss and lichens from a cedar roof. Water by itself should be adequate to remove the dirt and moss.

Never use chlorine bleach, laundry or other detergents or any harsh chemicals on any roof, especially cedar. The chemicals can become embedded in the grain, even after rinsing. Once they are engrained, they will continue working for many years.

If the chemicals are used, you can count on reducing the life of your cedar roof by many years and the appearnace of the roof can be ruined.

Once powerwashing is completed, the roof must be treated soon with a roof protectant or the roof will soon need to be replaced !

The reason for this is that there is a very thin layer of natural protection on the outer surface of the shakes by design. Power washing often removes that protection and leaves the inner fibres exposed to the UV of the sun. This would be very similar to removing the out layer (the epidermis) of our own skin. The proper treatment within a reasonable time is essential.

I cannot say often enough that power washing must be performed by a person trained in performing such activities on cedar roofs. Just because a person can power wash your driveway or siding does not mean they know anything about cedar roofs.

Much of the controversy over powerwashing cedar roofs has been generated by the results of people who do not know what they are doing. Get references before you let them on your roof!

Never Never Never use chlorine bleaches or other harsh chemicals on cedar roofs!