Massachusetts Building Code - Roofing and Reroofing Provisions
Pick the right code path first
Massachusetts roofing work is governed by 780 CMR, the Massachusetts State Building Code. One- and two-family dwellings and townhouses follow 780 CMR 51.00, the Massachusetts Residential Code (IRC-based, Chapter R9 for roof coverings). Everything else follows 780 CMR 34.00, the IBC-based volume, Chapter 15. Massachusetts amendments printed at the front of each volume override the model text, so a purely model-code answer can be marked wrong.
Reroofing rules
- A building permit from the local building official is required before re-roofing; the permit names the licensed supervisor and the scope.
- IRC R907 limits overlay: generally no more than one new layer over an existing covering, and only where the existing covering and sheathing are sound and the assembly stays within structural and fire limits.
- Stripping to the deck triggers replacement of deteriorated sheathing and new underlayment; you cannot shingle over rotten wood or failed flashing.
- Ice-barrier underlayment at the eaves (R905.1.2) applies across most of Massachusetts because of the winter climate.
Worked example
A 1920 two-family with two existing shingle layers and soft sheathing at the eave. Code path: 780 CMR 51.00. Two layers already exist, so a third is not permitted - full tear-off. Deteriorated sheathing is replaced, ice-and-water membrane runs from the eave to 24 inches inside the interior wall line, then new underlayment and shingles per the manufacturer's listing.
Traps
Assuming IBC Chapter 15 applies to a duplex; skipping the permit because the job is only shingles; and arguing that because the old roof had no ice barrier the new one does not need it.