Wood Shakes vs. Wood Shingles: Cedar Roofing Pros, Cons, and Fire Ratings

Cedar shakes are split and rough-faced, cedar shingles are sawn and smooth, but the fire rating decides a cedar roof before looks do. The Cedar Shake and Shingle Bureau’s fire-retardant Certi-Guard labels show Class B or Class C, so if your building department, HOA or insurer requires Class A, those labels alone do not meet the rule. Keep three things apart: the treatment label on the bundle, the fire class of a tested roof assembly, which can depend on what goes beneath the cedar, and the class your jurisdiction or insurer requires; the fire section below shows how to get each in writing.

The case for cedar is the look and texture of natural wood. The case against it is what that wood asks of you: fire labels that, for the bureau’s treated products, read Class B or Class C, and upkeep to keep the roof dry, clear of debris and watched for runoff, all covered below. Once fire rules allow cedar, the choice turns on the grade label, the roof’s pitch, and whether you can keep a wood roof dry and clear. If the fire rules rule cedar out, the roofing materials comparison lays out what else fits your house.

Shakes, Shingles, and the Grade Label on the Bundle

Shakes and shingles come from the same wood and differ in how they are made and how they look on the roof. A split shake has an irregular, textured face; a sawn shingle is thinner and more uniform, which gives a tighter, finer pattern. Either one sheds water by overlap and needs a pitch steep enough to drain.

Grade matters more than the shake-or-shingle label, and it is printed on the bundle. The Cedar Shake and Shingle Bureau’s Certigrade shingle grades are:

Those are the bureau’s grades for sawn shingles. For shakes, ask the supplier for the bundle’s grade label and the CSSB documentation that defines that grade, and write the grade into the contract.

The pitch floor applies to both products. Seattle’s adopted 2021 Residential Code, Chapter 9 sets 3:12 as the minimum slope for wood shingles and for wood shakes. Seattle’s text is the 2021 International Residential Code with city amendments, and your town may enforce a different edition, so confirm the slope with your building department.

Fire Ratings: What Treated Cedar Can and Can’t Reach

Roof fire classes describe how a covering resists fire from outside. UL’s roof ratings summary defines Class A coverings as effective against severe fire test exposures, Class B against moderate and Class C against light, under UL 790, the parallel of ASTM E108 (E108-25 was the active edition as of 2026).

Cedar’s documented fire classes come through treatment. The bureau describes Certi-Guard products as pressure-impregnated with fire-retardant polymers, with a red label for Class B and a blue label for Class C. Three label traps follow from that:

1. Blue means two things. A No. 1 Blue Label marks the top grade. A blue Certi-Guard label marks Class C fire treatment. A premium-grade bundle is not a fire-rated bundle unless it also carries the Certi-Guard label.
2. Preservative is not fire-retardant. Certi-Last is preservative-treated against decay and, per the bureau, not fire-rated.
3. The class belongs to the tested product. A bundle with no fire-retardant label has no fire class you can document. Treat it as unrated until a listing shows otherwise.

If someone offers a Class A cedar assembly, ask for the written listing that names the exact product and roof assembly tested. A verbal “it’s Class A with the right underlayment” is not a document you can hand to a building inspector or insurer.

The bureau also says the treatment is meant “to provide permanent fire protection.” That is the industry’s own description, so ask the supplier for the listing document and any conditions attached to it, such as cleaning methods or coatings that should not be applied over the treated wood. A rated roof keeps its rating through repairs only if the replacement pieces carry the same grade and the same fire-treatment label; ask the repair contractor to show you the labels on the replacement bundle before work starts, and keep a photo of them with your roof records.

Fire treatment narrows the gap; it does not close it. Class B and Class C ratings mean the covering passed less severe test exposures than Class A, which matters most where wind-driven embers are the threat.

Is Cedar Allowed on Your House?

Four parties can rule cedar out, and each answers separately. Ask all four in writing which fire class, if any, they require, then match the answer to the label on the bundle.

• Building department. Wildfire-area rules and local amendments can set a minimum roof fire class. The roof is where a house is most vulnerable to wildfire, according to CAL FIRE’s home hardening guide. Ask for the requirement in writing for your address.
• HOA. Covenants can restrict material and appearance, and some set fire requirements of their own. Get written approval for the exact product, grade and treatment.
• Insurer. Ask whether a wood roof, treated or untreated, changes your eligibility, premium or wildfire terms, and keep the reply.
• Historic district review. A historic board may require wood to match the original roof, which can make cedar the required choice rather than a banned one. Our guide to historic roof repair and replacement explains how that review works.

If you live where wildfire is a real threat, the roof covering is only one piece. Vents, gutters, roof edges and debris all decide whether embers find fuel; wildfire-resistant roofing covers the whole roof.

Upkeep, Drying, and Runoff

Cedar’s life depends on how quickly it dries after each wetting. Shade, leaf litter, moss and clogged gutters hold moisture against the wood, and wood that stays damp decays and splits sooner than wood that dries.

InterNACHI’s estimated life expectancy chart lists wood roofs at 25 years, as a guideline rather than a guarantee. Upkeep and drying conditions decide where your roof lands against that number.

Wet cedar and moss are slick, and shakes split under foot traffic, so replacing pieces belongs to a crew with fall protection. Keep your own upkeep at ground level, or on a ladder set on firm, level ground at the eave and never stepped off onto the roof:

• Look from the ground with binoculars for split, cupped, curled or missing pieces, and for moss or debris piling up in valleys and behind chimneys.
• Keep gutters and the roof edge clear of debris, which helps drying and, in fire areas, removes ember fuel. CAL FIRE’s guide makes the same point about plant debris in gutters.
• Ask about airflow under the roof. Cedar dries from both faces, so ask the installer which deck and underlayment arrangement the bureau’s installation manual calls for on your roof, and confirm your attic venting with our attic ventilation guide.
• Leave cleaning and moss treatment to a pro, and never pressure-wash cedar. High pressure strips wood fibers and drives water into the roof. How cleaning methods and moss chemicals compare is covered in the roof cleaning guide.

Runoff is the other upkeep question. A 2014 Washington State Department of Ecology study, summarized in its blog on copper and zinc, found arsenic and copper in runoff from treated wood shakes. If roof water feeds a rain barrel, a vegetable bed or a nearby stream, ask the supplier what the treatment contains and route downspouts away from those spots.

Cedar, Treated Cedar, or a Different Roof?

Start with the written fire answers, because they can end the choice:

• If any of the four parties requires Class A, the Certi-Guard Class B and Class C labels do not meet it. Choose a material with a Class A listing for its tested assembly; synthetic shake is one look-alike to evaluate on its listing, not its brochure.
• If Class B is required, specify Certi-Guard red-label product in the contract and check the label on delivery.
• If no class is required but you are in a wildfire area, weigh treated cedar against Class A options anyway, since the rule sets a minimum and the threat does not follow the rule.
• If your pitch is below 3:12 on any plane, cedar is out for that plane.
• If a historic board requires wood, get its written requirement for grade, size and treatment before bidding.

When cedar is allowed and you choose it, the contract should name the grade label, the fire-treatment label if one is required, and the deck and underlayment arrangement. Check the bundle labels against that contract when the material arrives, before it goes up.

This guide is general information for U.S. homeowners, not legal, insurance, tax, or engineering advice. Codes, laws, and policy terms vary by location and change over time; confirm details with your local building department, your insurer, or a licensed professional.

Sources

• Certigrade Shingles, Cedar Shake and Shingle Bureau
• 2021 Seattle Residential Code, Chapter 9: Roof Assemblies, City of Seattle Department of Construction and Inspections
• Roof Ratings, UL
• Wildfire Home Hardening Guide, CAL FIRE
• InterNACHI’s Standard Estimated Life Expectancy Chart for Homes, International Association of Certified Home Inspectors
• Cu L8r, copper and zinc, Washington State Department of Ecology