Permit
A permit from Cambridge
The residential code’s permit-exempt list (R105.2) has no roofing line. The application to Cambridge’s building department carries the contractor’s HIC number (R105.3).
Roof Replacement in Cambridge, MA
Half of the 54,840 homes in Cambridge were built before 1950. The rules below decide how much of the old roof has to come off and what goes under the new one.
New Roofing Costs connects homeowners with independent local roofing contractors. We do not perform roofing work.
Call (833) 781-1806 Replacement and new roofs only · homeowners
This number connects homeowners who are planning a new roof or a full roof replacement with independent local roofing contractors. It is not for leak repairs or patch jobs. The call must come from the homeowner who decides on the roof. Calls may be recorded.
The rules for a reroof in Cambridge
Layers
One old layer can stay; two cannot
A new roof may go over one existing layer; with two or more, or over slate, clay or cement tile, everything comes off to the deck (IRC R908.3.1.1). 68% of Cambridge’s homes were built before 1980, so count the layers before comparing quotes.
Source: IRC 2021, Chapter 9 (Pennsylvania edition, UpCodes); 780 CMR 51.00, Chapter 9 amendments
Ice barrier
Required statewide
There is no local exception: the state table says “yes.” Membrane or doubled underlayment, eave to 24 inches inside the wall line (IRC R905.1.2), is a line on every quote here.
Source: 780 CMR 51.00, Chapter 3 amendments (Tables R301.2(1) and R301.2(2)); IRC 2021, Chapter 9 (Pennsylvania edition, UpCodes)
Wind and snow
120 mph design wind, 40 psf ground snow
Cambridge’s code design values are a 120 mph ultimate design wind speed and a 40 psf ground snow load (30 psf minimum flat-roof snow load). At that wind speed the code calls for asphalt shingles labeled ASTM D7158 Class G or H (Table R905.2.4.1).
Source: 780 CMR 51.00, Chapter 3 amendments (Tables R301.2(1) and R301.2(2)); IRC 2021, Chapter 9 (Pennsylvania edition, UpCodes) (780 CMR 51.00, Table R301.2(2))
Rules as read on October 24, 2026. Everything else the state requires: roof replacement in Massachusetts.
Homes and roofs in Cambridge
Owners live in 16,547 of Cambridge’s occupied homes, or 34%. By year built, 47% before 1940, 54% before 1960, 68% before 1980; 20% went up in 2000 or later. (ACS 2020–2024.)
By building type: 10% detached houses, 7% attached single-family houses (rowhouses, twins and townhouses), 29% buildings of two to four units.
On a house built before 1940, ask what the deck is (boards or plywood) and whether slate sits under the later layers: slate can’t be roofed over.
Of the 54 Middlesex County municipalities on this site, Cambridge has the 21st largest share of homes built before 1980: 68%, against a county range of 29% to 87%.
ZIP codes: 02138 · 02139 · 02140 · 02141 · 02142
Cambridge and the towns around it
| Place | Median built | Before 1980 | Owners | Row, twin | Hail days |
|---|---|---|---|---|---|
| Cambridge | 1950 | 68% | 34% | 7% | 13 |
| Somerville | 1938 | 80% | 34% | 4% | 12 |
| Watertown | 1947 | 78% | 48% | 10% | 11 |
| Medford | 1942 | 76% | 54% | 7% | 10 |
| Belmont | 1938 | 87% | 65% | 6% | 11 |
| Arlington | 1945 | 86% | 62% | 7% | 9 |
Median built: median year the homes were built. Before 1980: share of homes built then. Owners: share of homes that are owner-occupied. Row, twin: share of homes that are rowhouses, twins or townhouses. Census ACS 2020–2024. Hail days: days with hail of 1 inch or larger within 10 miles, 2006–2025, NOAA Storm Prediction Center.
Storm record around Cambridge
Within 10 miles of Cambridge, hail of an inch or more was reported on 13 days between 2006 and 2025, the biggest stones 2 in on August 4, 2015. The most recent was August 23, 2020.
Severe Winter Storm and Snowstorm (DR-4379, July 2018) is the latest of 8 federal storm declarations covering Middlesex County since 2006. (OpenFEMA.)
A report says hail fell near Cambridge, not that it damaged a roof. When wind or hail damage means a new roof.
What goes on the roof next
Lifespans come from HUD’s capital-needs table, not from a brochure. More in the guides to shingles, metal, slate and flat roofs.
| Material | HUD useful life | Fits a house like | Watch for |
|---|---|---|---|
| Asphalt shingles | 20 years | Most pitched roofs; 10% of homes here are detached | Class G or H at 120 mph design wind (IRC Table R905.2.4.1) |
| Metal (standing seam, panels) | 50 years | Simple roofs with long, unbroken slopes | Standing seam that carries its own loads can skip the tear-off (R908.3.1) |
| Slate | 75 years | Older houses; 47% here predate 1940 | Can’t be roofed over; check the framing for the weight |
| Flat roof: EPDM or TPO | 15 years | Porches, additions, low-slope rears | Coating is not a replacement |
Checking a contractor in Massachusetts
Two numbers to ask for in Cambridge: the HIC registration (M.G.L. c. 142A, for owner-occupied homes of one to four units) and the construction supervisor license (CSL) with the roof covering specialty.
The price side is in what a new roof costs in Massachusetts; the paperwork side in checking a roofing contractor.
Questions about a new roof in Cambridge
Does a roof replacement in Cambridge need a permit?
A permit from Cambridge. The residential code’s permit-exempt list (R105.2) has no roofing line. The application to Cambridge’s building department carries the contractor’s HIC number (R105.3).
Can a new roof go over the old one in Cambridge?
A new roof may go over one existing layer; with two or more, or over slate, clay or cement tile, everything comes off to the deck (IRC R908.3.1.1). 68% of Cambridge’s homes were built before 1980, so count the layers before comparing quotes.
How old are the houses in Cambridge?
By the Census Bureau’s American Community Survey (2020–2024), the median home in Cambridge was built in 1950, 68% of homes were built before 1980, 34% are owner-occupied.
How many hail days has Cambridge had?
Hail of 1 inch or larger was reported on 13 days within 10 miles of Cambridge from 2006 through 2025 (NOAA Storm Prediction Center). A report means hail fell nearby, not that a roof was damaged.
How do I check a roofing contractor in Cambridge?
Two numbers to ask for in Cambridge: the HIC registration (M.G.L. c. 142A, for owner-occupied homes of one to four units) and the construction supervisor license (CSL) with the roof covering specialty.
What they will ask on the phone
- Your address or ZIP code in Cambridge
- How many stories the house has, and whether it is detached or attached
- The roof you have today, shingle, metal, slate, tile or flat, and its rough age
- The number of layers, if anyone has counted
- Your timing for a complete replacement
- Any historic-district or HOA rules on the house in Cambridge
- That you own the home and decide on the roof
The full list: before you call.