My father received a quote for work to be done to his roof and we both are a bit skeptical of the proposal. A firm would to come and power-wash the roof of the house and garage and spray on a product called 'Timber Pro UV Natural Wood Oil and Resin. The roof has treated cedar shingles and is only 10 years old. I already read your warning in your Q&A’s about power washing and would like your opinion about spraying on a coating. Would this not just wash off with the next rain shower?
It is my opinion that you shouldn’t power wash cedar shingles or shakes nor should you apply any sealer coatings. The treated shingles on your roof do not require maintenance of this type at all. The pre-treating of cedar shingles protects the roof from fungal rot.