Signs your garage roof needs replacing
- Curling, cracked or missing shingles
- Moss, soft spots or a roof line that sags between rafters
- Water on the floor or on things stored in the garage
- Rotten fascia boards or a missing drip edge
- A garage roof that's older than the house roof
Shingles or a low-slope roof?
Many garages have a lower pitch than the house. Asphalt shingles need a slope of at least 2 in 12 under Michigan Residential Code R905.2.2. Lower-pitch shingle roofs need additional underlayment protection; ask the roofer to specify the product and application. Flatter roofs need a suitable low-slope system, such as modified bitumen, EPDM or TPO.
A good estimate says which system suits your garage's pitch and why. If the pitch is borderline, ask about both options.
An unconditioned detached garage has an exception to the ice-barrier requirement in R905.1.2. Ask which protections suit the garage rather than assuming it needs the same assembly as the house. These references use the 2015 Michigan Residential Code, listed on LARA's current code-books page, checked October 2, 2026.
How much does garage roof replacement cost?
A garage roof is smaller and usually simpler than the house, so the total is a fraction of a house roof. But some costs don't shrink with the size: setup, a dumpster or haul-away, any permit, and the roofer's minimum charge. That's why the price per square (100 square feet) is often higher on a garage than on a house.
What changes the price:
- Roof area and pitch, and whether it needs shingles or a low-slope membrane
- How many old layers come off
- Decking replacement, which is common on older garages
- Fascia, drip edge and gutters, if they're part of the job
- Access down a narrow driveway or from an alley
For comparison, see the published house roof ranges on the roof replacement cost guide, and ask for the garage as its own line item.
With the house, or on its own?
Doing the garage and the house together usually saves on setup and disposal, and the roofs match. If the house roof still has years left, replacing just the garage makes sense, especially if it's leaking onto things you store.
Decking, fascia and gutters
Older garages often have plank decking or boards that have been wet for years. Expect the roofer to check the decking once the old roofing is off, and ask how any replacement will be priced. Rotten fascia and missing drip edge are worth fixing at the same time.
Common questions
Can new shingles go over the old ones on my garage?
A single existing layer and sound decking are starting points, but the roofing system must also be suitable. Michigan Residential Code R908.3.1.1 prohibits a re-cover over two or more existing layers. Ask how the decking will be checked before considering an overlay.
Do I need a permit for a garage roof?
Ask your roofer. Permit requirements are set by the City of Royal Oak's Building Division, or by your own city if you're nearby.
Will the garage roof match the house?
If both are done together, they can use the same shingle. If only the garage is being replaced, ask the roofer how closely they can match the house, or plan the garage to match the house's next re-roof.
Can the gutters be replaced at the same time?
Many roofers can replace gutters and fascia during the same job. Ask for them as separate line items so you can see what each part costs.
How long does a garage roof take?
A typical detached garage is often done in a day, weather permitting. Rotten decking, a low-slope membrane or combining it with the house can add time.
Related guides
- Rubber roofs and flat garage roof optionsEPDM rubber against TPO, modified bitumen and built-up roofing for a low garage roof, with published costs, lifespans and the slope rules.
