The short version
- The Residential Code of Ohio allows no more than two layers of shingles in total.
- No overlay if the old roof is water-soaked or deteriorated.
- An overlay hides rotted decking and makes the next replacement cost more.
- A full tear-off is the only way to see and fix what's under the shingles.
How many layers of shingles are allowed in Ohio?
Two at most, and only sometimes. Residential roofs in Ohio fall under the Residential Code of Ohio. Under it, a new layer of shingles can't go over the old roof if the roof already has two or more layers, or if the existing roof is water-soaked or deteriorated. Ohio city guides summarize it simply: no more than two layers of shingles in total. If you already have two, both have to come off.
Local permit rules vary: some cities don't require a permit to re-shingle, while the City of Columbus requires one to replace a roof. See Columbus permit rules.
Why an overlay is tempting
It's faster and cheaper because nothing gets torn off or hauled away. For someone selling soon whose roof has a single layer of shingles that still lies flat and is in sound condition, that can be a reasonable choice.
The downsides
- You can't see the decking. Rotted or soft wood stays hidden under the new roof and keeps getting worse.
- Leak protection is harder to do right. The ice barrier at the eaves, new flashing and drip edge all work best installed on bare decking.
- Bumps show through. New shingles follow the shape of the old ones, and curled or cupped shingles telegraph through.
- More weight on the roof structure.
- The next roof costs more. When it's time to replace, there are two layers to tear off and dispose of.
- Warranty and insurance questions. Some manufacturer warranties and insurance policies treat overlays differently. Check before you decide.
Our approach
We do a full tear-off on every replacement. We strip the roof to the decking, replace any rotted wood, and install ice barrier, underlayment, flashing and ventilation on a clean surface. It costs more up front, and it's the only way to know what's under your roof.