Weymouth · Norfolk County

Can you build an ADU in Weymouth?

Weymouth adopted its ADU ordinance on 3 February 2025, one day after the state law took effect. It permits ADUs as of right, but runs site plan review and design review with a public hearing on every one, which makes it the slowest of the towns documented here.

What the state guarantees you

Since 2 February 2025 this applies in every Massachusetts community. A town may be more generous than this. It may not be less.

Rule	What it means
Allowed by right	One ADU in single-family zoning districts, statewideNo special permit and no public hearing for a protected-use ADU
Maximum size	900 sq ft, or 50% of the principal dwelling, whichever is smallerA town may allow larger. It cannot allow smaller
Owner occupancy	A town cannot require itSo you may rent both units, or live in the ADU and rent out the house
Parking	One space at most, and none at all within half a mile of transitA town cannot ask for more than this
Short-term rental	The state leaves this to each townAll six towns documented here ban it, and two of them ban it for the main house too
In force since	2 February 2025Any conflicting local zoning became unenforceable that day

What Weymouth adds on top

Rule	In Weymouth
Where allowed	As of right anywhere a single-family use is allowed
Maximum size	900 sq ft
Inside an existing structure	Limited to one third of that dwelling's gross floor area
Public hearing	Required. Site plan review and design review on every ADU
Hearing timing	Held within 30 days of the application
Decision timing	Within 45 days of the hearing
Parking	None required if any part of the lot is within a half mile of a transit station
Short-term rental	Prohibited, for the ADU and the principal dwelling
Lot division	The ADU and the house must stay on one lot

Two things here catch people out. The one-third rule for a conversion inside the existing house is tighter than the 50% most people have read about, so a basement or attic conversion is capped lower than a new detached build. And the short-term rental ban reaches the principal dwelling too, not just the ADU, so building one takes your own house off Airbnb as well. Budget around eleven weeks from filing to decision if both clocks run their full length.

Questions people ask

Does Weymouth require a public hearing for an ADU?

Yes. Although an ADU is permitted as of right, Weymouth requires site plan review and design review with a public hearing on every application. The hearing is held within 30 days of the application and a decision follows within 45 days of the hearing.

How big can a Weymouth ADU be?

Up to 900 square feet. An ADU created inside an existing dwelling is further limited to one third of that dwelling's gross floor area.

Can I short-term rent my house if I build an ADU in Weymouth?

No. The prohibition covers both the ADU and the principal single-family dwelling.