Certificate of Occupancy in Somerville, MA: What It Is and When You Need One
A certificate of occupancy in Somerville MA: what it is, when the City requires one, final inspections, open permits, and how to check permit history.
Mateus MagnoLicensed Construction Supervisor · October 20, 2026 · 4 min read
A certificate of occupancy (CO) is the document the building commissioner issues after inspection saying a building, or a new part of it, can legally be used or lived in. In Somerville and the rest of Massachusetts you need one for new buildings, new units and changes of use. Most ordinary renovations end with a final inspection and sign-off instead.
A certificate of occupancy in Somerville, MA is the City's official OK that a building, or the new part of it, was inspected and can legally be used. You need one for new construction, a new apartment or a change of use. A kitchen or bath that doesn't change how the building is used usually ends with a final inspection instead.
I'm Mateus Magno, a licensed Construction Supervisor working out of Davis Square. I close out permits with the City all the time, so here is how it really works.
What is a certificate of occupancy in Massachusetts?
The rule comes from Section 111 of the state building code. In the residential volume, 780 CMR 51.00, Section R111, it says:
- No occupancy without it: a building can't be used or occupied, and its occupancy classification can't change, until the Building Commissioner or Inspector of Buildings issues a Certificate of Occupancy and Use. A local inspector can't sign one.
- Ten days: once the inspection finds no violations, the certificate is issued within ten days. It lists the permit number, address, owner, the part of the building covered and the code edition.
- Temporary CO: part of a job can be occupied early under a temporary certificate good for up to 180 days. It can be extended in 30-day periods on written request.
- It can be revoked if it was issued in error, based on wrong information, or the building is in violation.
- Exception: no CO is needed for permit-exempt work or for alterations that don't change the occupancy.
When does Somerville require a certificate of occupancy?
Section R111.1.1 calls for a new CO when a building is changed in whole or in part, moves to a different use group or a different use, or takes on more live load or more occupants. On Somerville jobs that usually means:
- A new house or a new building on the lot.
- A new dwelling unit: a basement or attic apartment, or a backyard ADU (see my basement apartment guide).
- Turning a two-family into a three-family, or a triple-decker into condos.
- Changing a storefront or office into housing, or the reverse.
The City's Building Division fee schedule (effective 1/1/2025) prices the certificate:
| Certificate of occupancy | Somerville fee |
|---|---|
| Residential, 1–3 units | $130 |
| Condominium units | $130 per unit |
| Residential, 4+ units | $130 for the first 3 units, plus $25 per unit after 3 |
Final inspection and certificate of completion
Most renovations don't change the use. For those, R110.3.10 requires a final inspection once the permitted work is complete and before anyone occupies the space. Under R111.1.2, the building official may then issue a Certificate of Completion saying the work matches the permit and no more inspections are needed.
Keep in mind that the electrical, plumbing and gas permits each have their own final inspection. A job isn't really closed until every one of them is signed off.
You may also see "certificate of inspection" in City paperwork. That's a recurring safety inspection for certain building types. Somerville's fee schedule lists them for restaurants, assembly spaces, fire escapes, and multifamily (Use Group R-2) buildings on a five-year cycle.
Who gets the certificate of occupancy?
The Building Commissioner or Inspector of Buildings issues it, and the owner's name and address go on the certificate. The permit holder (usually your contractor) has to call for each inspection under R110.5. Ask for a copy of the CO or certificate of completion and keep it with your deed.
Don't confuse it with the smoke and CO alarm certificate you need from the fire department when you sell. The state Department of Fire Services guide covers that one, and it's a separate inspection.
Open permits that block a sale
An "open" permit is one that was issued but never got its final sign-off. Under R105.5, a permit becomes invalid if work doesn't start within 180 days, or stops for 180 days. Either way the record still sits in the City's system.
In my experience, buyers' attorneys and lenders do look for open permits, and the seller ends up rushing to close them before the sale. If the contractor is gone, a new licensed pro may have to take over the permit, and the inspector may want to see work that's already covered up.
How to check a Somerville property's permit history before buying
- Search the City's records. Somerville handles building permits through its CitizenServe portal.
- Use the open data. The Applications for Permits and Licenses dataset covers over 90,000 applications since 2014, with status and location. The City notes that where it disagrees with the public CitizenServe viewer, the viewer wins. (I used it for my analysis of Somerville's 7,174 recent permits.)
- Ask ISD. For pre-2014 records or a copy of a CO, contact the ISD Building Division at 1 Franey Road, (617) 625-6600 ext. 5600, [email protected].
- Compare the records to the house. A finished basement, a third kitchen or a new bath with no permit on file is a question for the seller.
Need a hand?
Whether you're buying, selling or closing out an old job, I can walk the property, check the permit trail and tell you what it will take. Book a free walkthrough and you'll usually have a written line-item budget within 48 hours.
Frequently asked questions
What is a certificate of occupancy?
It's the document a building commissioner issues after inspection saying a building, or a new part of it, can legally be used or occupied. In Massachusetts the rule is Section 111 of the state building code (780 CMR).
Who issues the certificate of occupancy in Somerville MA?
The Building Commissioner or Inspector of Buildings at Somerville's Inspectional Services Department issues it. The owner's name and address go on the certificate, and the permit holder requests the inspections.
Do I need a certificate of occupancy for a renovation in Massachusetts?
Not usually. The code doesn't require a CO for alterations that don't change the occupancy. A renovation instead gets a final inspection and may get a Certificate of Completion. New units and changes of use do need a CO.
How much is a certificate of occupancy in Somerville?
The City's fee schedule effective January 1, 2025 lists $130 for residential buildings with 1–3 units and $130 per condominium unit. Buildings with 4 or more units pay $130 for the first three units plus $25 for each unit after that.
Mateus Magno is the founder of Magno & Co — a licensed Massachusetts Construction Supervisor (CS-123658), registered Home Improvement Contractor (HIC #220484) and certified Lead-Safe Renovator Supervisor who has renovated and managed over $3 million in projects across Greater Boston.
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