Shakes or shingles: two different roofs
Both are cedar and both are sold by the square, but they are made and laid differently. Shakes are split from the block along the grain, at least on the face that shows, so they are thick, rough and uneven, and the roof casts deep shadow lines. The usual product is hand-split and resawn: split on the face, sawn flat on the back. Shingles are sawn on both faces, thinner and smoother, and laid with a shorter exposure for a flat, even look.
The difference goes beyond looks. A shake roof has gaps behind its rough faces, so it needs interlayment, which a shingle roof does not. Thickness is lifespan, too: a heavy shake has more wood to weather away than a medium one. This page prices shakes.
Grade is printed on the bundle label. The top grades are cut entirely from heartwood with vertical grain, which resists rot and stays flat as it weathers; lower grades allow flat grain and sapwood, which cup and decay sooner. The spread in the shake line is mostly grade and thickness, so a quote should name both.
The layers under and between the shakes
From the deck up, the roof goes together like this. Self-adhered membrane ($533 to $752) runs along the eaves, where ice dams back water up in cold climates. Felt covers the rest of the deck. Then every course of shakes gets an 18-inch strip of heavy felt laid across its upper part, under the joints of the course above, to turn back any water that blows through. The strip has to stop short of the butts of the next course or it wicks water. The felt line, $80 to $140, covers both the field underlayment and the interlayment.
Under all of that is the choice between spaced and solid sheathing. Traditional shake roofs went on boards with air gaps between them, so the underside of every shake dried after rain, and that drying is much of why the old roofs lasted. Solid plywood or OSB is more common now, and it is needed under the eave membrane and under some fire-rated assemblies. Over a solid deck, many installers add a ventilation mat or battens so the shakes do not sit wet against it. The estimate reuses the existing deck: new spaced boards, battens, a mat or rotten-board replacement are extra.
Question the nails on any quote. Cedar contains natural acids that eat through thin electro-galvanized coatings, and treated shakes can be harder on fasteners still, so shake makers call for stainless steel or hot-dipped galvanized nails long enough to pass through the shake and well into the deck. The estimate carries 2-inch hot-dipped ring-shank nails at $84 to $144; stainless costs more again and is the safer choice near salt air. A quote that lists plain roofing nails for shakes is a quote to ask about.
Check the fire rules before anything else
Untreated cedar burns, and in wildfire country that settles more cedar roofs than taste does. Some states and many local jurisdictions restrict wood roofs in fire-prone areas, require a Class A roof assembly, or ban wood shakes outright. Check local code with the building department before choosing cedar, and before asking anyone to price it.
Fire-retardant-treated shakes are pressure-impregnated with chemicals that slow ignition. Installed over the underlayment or cap sheet the manufacturer tested them with, the assembly can earn a Class B or Class A rating. The rating belongs to the whole assembly, not the shake, so a quote in a fire zone should name the treated product, its rating and the layers it depends on. Treated shakes cost more than the untreated shakes priced here.
Call your insurer as well. In fire-prone regions some insurers charge more for a wood roof or decline it. Where cedar is ruled out, metal is the usual choice, and some metal and composite products are pressed to look like shakes.
Living with a cedar roof
A cedar roof lives as long as it dries. Heavy shakes on a steep, sunny roof in a dry climate last decades; the same shakes under trees in a wet climate can be finished in much less, as moss and fungus hold water against the wood. Our guide to roofing materials puts wood at 25 to 40 years in a dry climate. IRC chapter 9 sets 3:12 as the minimum slope for shakes, and anything steeper sheds water faster and lasts longer.
Upkeep is regular rather than difficult: keep valleys and the gaps between shakes clear of needles and leaves, cut back overhanging branches, and replace split or missing shakes as they show up. Moss gets a cleaner made for cedar, never a pressure washer, which strips the soft surface wood. Some owners have the roof cleaned and treated with a preservative every few years, which slows weathering but cannot make up for a roof that stays damp.
Against architectural asphalt, cedar costs far more for a roof that will not reliably outlast it in a damp climate. The case for cedar is the look, the style of the house and, in some neighborhoods, what the street or a historic district expects.