Cedar Shake vs Composite Roofing in Minnesota

The word composite means two different things, and which one you mean changes the whole comparison. Cedar service life, what shortens it, what a Class 4 rating actually measures, the Minnesota discount rule most contractors get wrong, and the code detail that bites under a cedar roof.

Before you can compare cedar shake against composite, you have to settle what composite means, because the roofing industry uses it for two completely different products. Some manufacturers use it for ordinary asphalt shingles. Others use it as the category name for polymer shake that imitates cedar. So “cedar shake vs composite roof” is either a question about wood against asphalt, or a question about real cedar against a synthetic copy of it, and those are not remotely the same decision. Here is how to tell which one you are actually asking, and what separates the materials once you know.

Why nobody agrees on what “composite” means

This is not you being confused. The term has no settled definition, and the trade bodies decline to give it one.

The National Roofing Contractors Association’s glossary of roofing terms has no entry for “composition” at all, and its only “composite” entries are for insulation board and geocomposite, neither of which is a shingle. The Asphalt Roofing Manufacturers Association uses the word in the material science sense, describing asphalt shingles as “complex composite products made by combining materials with significantly different properties.”

Manufacturers then pull it in opposite directions. CertainTeed treats all three words as the same thing: “Asphalt shingles are also known as composition shingles (or composite shingles). These are general terms for the same thing.” DaVinci Roofscapes, meanwhile, uses composite as its own product category name for polymer shake and slate.

So both readings are legitimate. If a salesperson uses the word without explaining which one they mean, ask. The clearest way to frame it is by what the product is made of. Wood, asphalt, or polymer.

How long does a cedar roof last in Minnesota?

The Cedar Shake and Shingle Bureau puts average service life at approximately 30 to 40 years, depending on grade, installation quality, climate, exposure and maintenance. The USDA Forest Service’s Forest Products Laboratory reached a consistent figure independently, reporting that properly installed and maintained wood shakes and shingles “should last more than 30 years.”

Grade matters more than most homeowners realize, and the labels are specific. Certi-Split handsplit and resawn shakes have a rough split face and a sawn back, with Premium Grade meaning 100 percent edge grain, clear heartwood and no defects. Certi-Sawn tapersawn shakes are sawn both faces and thicker than a shingle. Certigrade shingles are sawn both sides, and here the Bureau is blunt: “there is no such thing as a Premium Grade shingle.” No. 1 is the top shingle grade. The Certi-label inspection mark is what ties a bundle to that grading system, backed by unannounced mill inspections.

Ask which grade you are being quoted. The gap between Premium edge-grain heartwood and a lower grade with flat grain and sapwood is most of the difference between the top and bottom of that 30 to 40 year range.

What shortens a cedar roof faster than the weather does

Almost everything that takes years off a cedar roof is a decision somebody made rather than weather it could not survive, and most of those decisions happen at installation or during well-meant maintenance. The short list is grain, ventilation and what gets put on the wood.

Flat-grain shakes shrink and swell roughly twice as much as vertical or edge grain, so they warp and split sooner. Sapwood content instead of all heartwood cuts decay resistance. Spray foam applied against the underside is a known problem: the Bureau’s position is that it “tends to create an air barrier and a non-ventilated base. This can lead to premature deterioration.” Moss and trapped debris hold moisture against the wood. Walking on the butt ends cracks them. Felt interlayment run too far down a course traps water against the shake, a failure the trade calls rot felting.

Then there is the mistake homeowners make with the best intentions. Do not seal a cedar roof. The Bureau states it directly: “Sealing the roof will lock in moisture that would otherwise naturally evaporate. Cedar needs to breathe.” The correct product is a water-repellent preservative, not a waterproofer. Improper power washing does its own damage, and the USDA is equally direct that loss of fiber “drastically decreases the life expectancy of the roof.” The Bureau also warns against spray-on topical fire retardants, which do not work, and against anything containing linseed oil, diesel or crankcase oil.

A cedar roof is a maintained roof. If nobody is going to clear the debris, control the moss and refinish it periodically, it will not reach the top of its range, and that is a fair reason to choose a different material rather than a reason to buy a cheaper cedar.

What a Class 4 impact rating actually measures

A Class 4 rating means the product survived a defined laboratory impact without opening up on its underside, and nothing more than that. It matters in a hail market like this one, and it is routinely described as more than it is.

UL 2218 drops steel balls of four diameters: Class 1 at 1.25 inches, Class 2 at 1.50, Class 3 at 1.75, and Class 4 at 2.00 inches, released from the height needed to match the kinetic energy a hailstone of that size would carry in a thunderstorm. Class 4 is confirmed at a 20 foot drop.

The part worth knowing is what counts as failing. Per the Insurance Institute for Business and Home Safety’s summary of the test, “Any evidence of opening, tearing, fracturing, cracking, or rupturing on the back of the shingle is recorded as a test failure. Crushed or dislodged granules, dents, or openings visible only on the top of the shingle, are not considered failures.” The test does not care about cosmetic damage. A Class 4 product can be visibly marked by hail and still be doing exactly what it was rated to do.

IBHS is also candid that UL 2218 does not predict real hail performance well. It runs a separate protocol using lab-manufactured hailstones with Good and Excellent style ratings rather than pass or fail, and states that protocol “is not intended for insurance claims or legal claims handling, product warranties, or legal standards.” Treat an impact class as a durability specification, not as a promise about how a hail claim will go.

Does Minnesota give you an insurance discount for an impact-resistant roof?

Not for the reason most people are told, and this is worth getting right before it influences your material choice.

Minnesota does have a statutory discount. Minnesota Statutes section 65A.298, enacted in 2023, requires insurers to provide a premium discount or rate reduction to an owner who builds, locates or retrofits a property meeting Fortified program standards including a hail supplement, as administered by IBHS. The owner submits an IBHS-issued FORTIFIED certificate and the insurer files actuarially justified rates.

What the statute does not do is grant a discount for simply installing a Class 4 shingle. The mandate attaches to a whole-roof FORTIFIED designation, not to a product class, and the FORTIFIED hail supplement itself calls for shingles rated Good or Excellent on the IBHS hail ratings rather than Class 4 as such. A separate state program, the Strengthen Minnesota Homes Act, funds retrofits through the Department of Commerce.

If a contractor tells you a Class 4 shingle triggers a Minnesota discount, they are describing something the statute does not say. Your carrier may still offer a voluntary discount, which is a fine reason to ask them. It is not a legal entitlement.

The Minnesota code detail that decides a cedar job

Minnesota adopts the 2018 IRC and makes no state-specific amendments to the wood shake or wood shingle sections, so the national text governs, and one line of it bites hard here.

For wood shingles and wood shakes, the code requires solid sheathing in areas where the average daily temperature in January is 25°F or less, across that portion of the roof requiring an ice barrier. The Minneapolis and St. Paul January normal mean temperature is 15.6°F per NOAA’s 1991 to 2020 normals. Solid sheathing under the ice barrier zone is therefore a code requirement on a cedar roof in this market, not a preference, and traditional spaced sheathing alone will not satisfy it at the eaves. The ice barrier itself has to run at least 24 inches inside the exterior wall line, or 36 inches measured along the slope on pitches of 8:12 and steeper.

Now the tension. The Bureau is emphatic that you must not cover the entire deck with non-permeable underlayment, because cedar has to dry from beneath. Self-adhered eave protection belongs at eaves and valleys only. So the assembly has to satisfy a code-required ice barrier at the eaves and full back-ventilation everywhere else, at the same time. Attic ventilation runs 1:150 net free area to attic area as the general rule, or 1:300 for a properly balanced intake and exhaust system, and 1:150 becomes the minimum if any barrier sits above the deck.

This is the real reason cedar jobs go wrong in Minnesota, and it has nothing to do with the wood. Ask any contractor quoting cedar to tell you exactly how they are handling the eave detail and the ventilation. If you want the wider picture of what happens above your ceiling, we covered it in attic ventilation and insulation for Minnesota roofs.

Fire ratings are not what people assume either

Untreated cedar shakes and shingles carry no fire class rating at all. Class A, B or C comes only from pressure-impregnated fire-retardant treatment, applied by a full-cell vacuum-pressure process under the code. The Bureau notes that Class B treated product is used within a specific assembly to produce a Class A system.

Asphalt is rated under ASTM E108 or UL 790, and the same caveat applies from the other direction. ARMA points out that Class A is an assembly rating dependent on underlayment and installation, not an intrinsic property of the shingle, and that where shingles are not installed consistently with those requirements “the installed roof system’s fire resistance may be unknown.” Both materials, then, are rated as systems. A number on a wrapper is not a rating on your house.

What about cost?

There is no honest published figure to give you. The Cedar Shake and Shingle Bureau publishes no cost figures and says so explicitly on antitrust grounds, and ARMA publishes none either. No authoritative cost-per-square range exists from any manufacturer, trade body or standards body for any of these three materials.

What can be said is what drives the number. Cedar is labor-intensive and grade-sensitive, and in this climate it usually requires deck work to meet the sheathing rule above. Synthetic shake sits in its own bracket and avoids the maintenance cycle entirely. Asphalt is the volume product and carries the widest range within itself. Get real quotes for your own roof and insist that each one states the grade or product line, the sheathing scope and the ventilation work, because two cedar quotes that look far apart are often quoting different jobs.

Choosing between them

If you want the look of cedar and you will maintain it, real cedar earns its place, provided the deck and ventilation are built correctly. If you want the look without the maintenance cycle, synthetic shake is the honest answer to that want. If what you actually care about is a durable roof at a sensible price in a hail-prone metro, asphalt is not the compromise choice people assume it is, and a high impact class is available there too.

We have a separate guide on cedar shake roofing, natural vs synthetic, which goes deeper on that particular fork if it is the one you are facing.

The step that comes before any of this is finding out what your existing deck, eaves and ventilation will support, since on a cedar roof the assembly underneath decides the outcome more than the wood does. If you are weighing a roof replacement anywhere from Ham Lake and Blaine out across the north metro, have someone get into the attic and onto the roof and tell you what is actually there first. Our inspections are free, and a fair number of them end with us telling people their roof has years left in it.