Maintenance FAQ


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.

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.

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.


Are oil based products any good for the roof?

There are a variety of options available for topical treatments. Refer to the CSSB’s Care and Maintenance Brochurefor the full guidelines available from this organization. Keep in mind that the CSSB does not recommend brand names of products.

I have a cedar roof on my home and it was recommended I have the shakes oiled. Is this a good idea?

In humid areas oiling shakes does not allow them to breathe and they cannot dry out properly which could shorten their life span. The CSSB recommends you try a good fungicide/preservative. Keep in mind that no by-products, such as motor oil, should be used on cedar roofs. Hot, dry climates tend to accept oils better than moist/humid climates, simply due to the fact that oils can seal unwanted moisture into the roof. Please see the CSSB’s Care & Maintenance Brochure.


Is it OK to nail down portions of shakes which have curled or bowed for them to lie flat again?

The CSSB recommends replacing the shakes if they are curled very badly.

We are having problems with our shakes cracking and falling off. What do we do?

This could be caused by the nails or the nailing technique used at installation. Contact your local Member Contractor/Installer for assistance.

Should my contractor be walking on my roof using cleated boots/shoes? Will the tiny holes compromise the longevity of our shakes?

Small indentations made by cleats usually rebound over time.

My roof was leaking and a relatively inexperienced contractor came out and sealed up large areas with a few tubes of caulk. Is this normal?

No. Caulk is used to seal small areas, not substitute for proper repairs. Caulk will not stick to unfinished wood; it is only a temporary fix for cedar. Caulking is used successfully on finished wood and on metal flashing. Contact an Member Contractor/Installer for more help.

Is it ok to walk on my shake roof to examine it as it ages?

The CSSB does not advise homeowners to walk on their roofs themselves; if a roof survey is needed, ensure that you hire a professional contractor to do this work for you as s/he has the proper safety equipment, training, and procedures to perform this work safely.

We have preservative treated shakes on our 10 year old roof and some of them are starting to split. Is there anything we can spray on them to help them last longer?

Some splitting of the shakes over time is normal. If the roof is not leaking then the splits are not doing any damage and should be left alone. A professional can insert metal shims under any wide splits if you consider it to be necessary.

How do you repair a very small section of a cedar roof?

See the repair diagram in the CSSB’s Care & Maintenance brochure.