Can moss buildup cause my roof to leak?

Heavy moss can cause water to back up the roof enough to run over the top of the shingles. The buildup should be removed. Moss retains soil and moisture that could harm the wood over time.

My cedar shake roof is surrounded by tall fir trees and the needles accumulate in the spaces between the shakes. Should I have these cleaned out periodically?

Yes, it is a good idea to have a professional clean the debris off your roof. Cedar needs to breathe, and therefore any accumulation of needles, branches, leaves and dirt will affect its lifespan.

What can I do to prevent moss buildup on my cedar roof?

Zinc or copper strips nailed at the ridge cap can be used to control moss for a limited number of courses. Reaction between rain and the zinc or copper forms a mild solution that is carried down sections of the roof for two or three feet. The optional use of these strips can be eliminated if you are using Certi-Last® products. Complete care and maintenance recommendations are available in the CSSB's Care & Maintenance Brochure.

Can I clean my roof with Bleach and Water?

Please refer to page 10 of  the USDA Forest Products Laboratory document for recommendations on cleaning solutions. 

How do I remove mold, moss or lichen from my cedar roof?

Please refer to the USDA Forest Products Laboratory documents below for recommendations on cleaning and maintenance solutions.

What will zinc or copper napthanate do to my roof?

A zinc or copper napthanate, in solution form, works to preserve your cedar roof and to retard future surface growth. Consult your local professional, competent contractor in your area.

Do I need a license to power wash and treat roofs?

You should check with your State's Contractor's Licensing Board to find out if what you are doing requires a license.

Can you recommend a good cedar roof preservative?

The CSSB does not recommend brand names. The CSSB does, however, recommend if using a topical treatment that it offers a MSDS (Material Safety Data Sheet that lists product ingredients and safety precautions), is labeled as a cedar roof treatment product, is a water repellent, UV inhibitor, and/or EPA registered wood preservative, and has a manufacturer's performance guarantee. Do not use a topical treatment that: makes outrageous claims (such as a 10 year effectiveness), makes fire-retardant claims, is a sealant, waterproofer or plasticizer, or contains unfortified linseed oil, diesel fuel or crank case oil.

Do I need to powerwash my cedar roof?

Powerwashing, done correctly, is one of the options available in the care and maintenance process. When done incorrectly, however, powerwashing can seriously damage a cedar roof. Check the CSSB's Care & Maintenance Brochure for care and maintenance guidelines.

Should I seal my cedar roof to keep out moisture?

No. Never seal your cedar roof. Sealing the roof will lock in moisture that would otherwise naturally evaporate during normal weather conditions. Cedar needs to breathe and thus a water repellant type product, rather than a water proofer is the best route to follow. See the CSSB's Care & Maintenance Brochure for complete topical treatment product guidelines available from the CSSB.

Can I use paraffin oil on my roof?

Yes, if it is a component of a proper cedar roof maintenance product. Check the CSSB's Care & Maintenance Brochure for guidelines. Paraffin is sometimes used as a carrier for active ingredients and will usually weather away within six months.