Can You Put a Metal Roof Over Cedar Shake?

Can you install metal roofing over cedar shakes?

No. Metal roofing should not be installed over cedar shakes or cedar shingles, and Interlock requires a full tear-off of any cedar roof. This is one of the cases where an overlay is simply not an option. The only roofing that may stay under an Interlock roof is a single layer of asphalt shingles, and only if an inspection finds it suitable. Cedar, natural slate and concrete tile always come off. That can surprise owners, because cedar roofs often look solid from the ground. But a cedar roof that is ready for replacement usually has split, cupped or missing pieces, soft spots and moss, and it may be laid over spaced boards rather than a continuous deck. None of that makes a sound base for a new roof, and covering it would hide problems that only get worse.

Why can't metal go over cedar?

Metal cannot go over cedar because cedar is uneven, compressible and holds moisture. Shakes in particular are thick and irregular, so a new roof laid on top would sit on high and low spots and could not be fastened evenly. Moisture is the bigger worry. Old cedar absorbs water and dries slowly, especially on shaded north slopes and under trees, which are common across New England. Sealed under a new roof, that wet wood would keep rotting, along with the deck below it. Fasteners would also have to pass through decaying wood to reach the deck, weakening their hold. And covering cedar means no one sees the deck, so rot, insect damage or old leak stains stay hidden. Tear-off is the only way to know what the roof is really sitting on.

What happens to the deck after cedar is removed?

Once the cedar is off, the crew inspects the deck and fixes whatever it needs before any new roofing goes on. Many older cedar roofs were laid on spaced boards, sometimes called skip sheathing, which let the wood breathe. Where the deck is spaced boards, it is usually covered with new sheathing to create a solid, continuous surface for underlayment and the metal roof. Rotted or broken boards are replaced either way. This is also the point to deal with attic ventilation. Older cedar roofs ventilated partly through the gaps in the wood; once the roof is solid, the attic needs proper intake and exhaust. That matters for moisture and for ice dams, which come from heat loss and poor ventilation rather than the roofing. We walk through these findings with you, including any extra work, before it is done.

How do you keep the cedar look with a metal roof?

You keep the cedar look by choosing a metal profile made to resemble wood. Interlock makes two: Cedar Shingle, which reproduces the flatter, sawn shingle look, and Shake, which reproduces the thicker, split, rustic texture of hand-split shakes. Our New England job book shows 102 Cedar Shingle and 15 Shake profile roofs, so they are a smaller share than Slate here, but they suit Capes, coastal cottages and farmhouses where wood has always been the look. Color makes a big difference. Colonial Brown and Tudor Brown give a fresh-wood or weathered-brown appearance, and Deep Charcoal can read like cedar that has grayed with age. Look at samples outdoors beside your siding. If your home is in a historic district, check with your local historic district commission before choosing a substitute for wood.

What do you gain by replacing cedar with metal?

Replacing cedar with aluminum mainly removes the upkeep and the vulnerabilities of wood. Cedar needs periodic cleaning and treatment, collects moss and debris in damp shade, and eventually splits, cups and rots. An aluminum roof does not rot or absorb water, does not rust in coastal salt air, and handles freeze–thaw cycles without cracking. It weighs roughly 0.4 to 0.7 lb per square foot. Fire performance is also different. Interlock roofs are Class A Fire Rated Available, as a complete assembly, which wood roofs generally cannot match without special treatment. Insurance is a separate question: ask your own insurer how a roof change affects your policy. The Guardian Lifetime Limited Material Warranty covers the material and finish for the original purchaser while they own the home, transferable once; workmanship is excluded.

What should you ask before hiring for a cedar tear-off?

Ask how the contractor will handle the deck, the debris and the ventilation, because those are where cedar jobs go right or wrong. A good answer covers how they check for spaced boards, what they do about rot, and how they vent the attic once the roof is solid. Check registration too. Massachusetts requires home improvement contractors to register under M.G.L. c. 142A for work on owner-occupied homes. Connecticut registers home improvement contractors through the Department of Consumer Protection, and Rhode Island through its Contractors' Registration and Licensing Board. New Hampshire and Maine have no state roofing license, so ask for insurance certificates and references. Condo owners in Massachusetts should get approval from their trustees or board first, since roofs are usually common area under Chapter 183A condominium documents.

Step by step

1. Have the roof, deck and attic inspected.
2. Choose a Cedar Shingle, Shake or other profile and color from outdoor samples.
3. Check with your historic district commission or condo board if either applies.
4. Remove all cedar, old underlayment and flashings.
5. Repair the deck, sheathing solid over spaced boards where needed.
6. Install underlayment, ice barrier, flashings, trim and the metal roof.
7. Review the finished roof and cleanup with the crew lead.

Common questions