On 11 Sep 2007 07:11:47 GMT, wrote Re Cedar shake
roof treatments?:

I was talking to a roofer about what to do with our ~25 year old cedar
shake roof and one option he offered was a "restoration" consisting of
pressure washing the existing shakes, replacing all damaged shakes and
felt, and spray-on treatment with a derivative of guanidine phosphate,
which is supposed to be UV protective, and decay and fire retardant.
They offer a 12 year warranty on the treatment.

Are these chemical treatments effective for older roofs? The quoted
price seemed potentially attractive compared to a new shake roof, but
not exactly cheap ($6K for 2700 sq ft). Maybe most of the value of
the "restoration" comes from the repair work?

A neighbor down the road had something like this done several years
ago. I don't know if it's the same treatment as you are considering.
The neighbor said the treatment lasted about two years. When he tried
to contact the roofer, the roofer had gone out of business.

I would replace the shake with something else.