ADU Rules in Hingham, MA
Yes. Hingham allows ADUs by-right up to 900 sq ft. Hingham has permitted ADUs since 2018. The friction is not zoning. It is coastal flood-zone rules, historic-district design review, septic capacity, and Hingham's local design standards.
Call BuildX: (781) 627-7000
Hingham allows ADUs by-right
Section V-K · amended April 28-29, 2025 Annual Town MeetingHingham did not just adopt an ADU bylaw. It updated one it has had on the books since 2018. At the April 28-29, 2025 Annual Town Meeting, Hingham amended Section V-K of the Zoning By-Law [Bylaw §V-K] to comply with the Massachusetts Affordable Homes Act [MGL 40A], removing the older special-permit and owner-occupancy requirements [ATM Amendment]. The amendment was approved and the Attorney General's Office signed off. Detached, attached, and interior-conversion ADUs are allowed by-right with a building permit, up to 900 sq ft or half the gross floor area of the main house, whichever is smaller.
Can I build an ADU in Hingham, MA?
Yes. Hingham allows detached, attached, and interior-conversion ADUs by-right with a building permit under Section V-K of the Zoning By-Law [Bylaw §V-K], up to 900 sq ft or half the gross floor area of the main house, whichever is smaller. No special permit is required for a compliant project. Hingham requires a minimum 30-day rental term, so short-term rentals are not permitted.
Show full bylaw history, citation, and state preemption note
Hingham's ADU rules live in Section V-K of the Zoning By-Law, pages 136 to 138 of the 2025 clean copy [Bylaw §V-K]. The history matters, because it tells you this is a town that knows how to permit an ADU:
- 2018: Original Section V-K adopted. Attached ADUs only.
- 2023: Amended to allow detached ADUs as well.
- April 28-29, 2025: Amended at Annual Town Meeting to comply with the Affordable Homes Act. Removed the special-permit requirement and the owner-occupancy requirement. Kept the 30-day minimum rental restriction.
Between 2018 and 2024, Hingham permitted roughly 17 attached family and caregiver ADUs, about three per year [Town ADU page]. The April 2025 amendment was a refinement of a working bylaw, not a launch.
One narrow state preemption note. Hingham's pre-2025 bylaw required owner-occupancy. Massachusetts state law (760 CMR 71.00) [760 CMR 71] preempts owner-occupancy requirements for protected-use ADUs, and the April 2025 amendment removed that requirement to align with state law. In practice, you may rent the principal dwelling and live in the ADU, or live in the principal dwelling and rent the ADU. Some older online sources still reference the outdated owner-occupancy rule. Confirm Hingham's current administrative posture with the Building Department at (781) 741-1420 before signing a lease.
For most homeowners, the practical answer is straightforward. A Hingham ADU at or under 900 sq ft, on a single-family lot in a residential district, is a by-right project. You do not need a special permit and you do not need a public hearing for a compliant project. You file one building permit with the Hingham Building Department.
Where Hingham ADU projects actually take work is in the design standards and the overlay reviews: the architectural style-continuity requirement, the detached-ADU placement rules, coastal flood compliance on waterfront parcels, Hingham Historic Districts Commission review in the historic districts, Title 5 capacity on septic-served parcels, and Conservation Commission filings inside the wetland buffer. A clean package is what moves a Hingham ADU quickly.
Garage conversion ADU
A common variation of either the detached or attached ADU paths, depending on the garage configuration. Hingham's bylaw does not treat garage conversion as a separate ADU category; it is classified based on whether the converted structure is attached to the principal dwelling.
- If the garage is attached to the house: Treated as an attached ADU, subject to the architectural style-continuity standard
- If the garage is detached from the house: Treated as a detached ADU, subject to the placement rules (minimum 10 ft from the main house, rear or set back from the front plane)
- Best for: Properties with a structurally sound existing garage; ability to reuse foundation, walls, roof; faster than ground-up construction
- Watch for: Foundation adequacy, insulation upgrades, entrance and stairway location restrictions, separate-entrance and bathroom plumbing additions, parking compensation if original spaces are lost, and design review if the parcel is in a historic district
Hingham ADU Rules at a Glance
The six things most homeowners ask first. Tap "View all rule details" for the complete data set.
View all Hingham rule details (15+ data points)
- ADU types allowed: Detached, attached, interior conversion
- Approval: By-right with a building permit. No special permit, no public hearing for a compliant project.
- Bylaw section: Section V-K (Accessory Dwelling Units), pages 136 to 138 of the 2025 clean copy
- Most recent amendment: April 28-29, 2025 Annual Town Meeting [Bylaw]
- Max size: 900 sq ft or 50% of the main house gross floor area, whichever is smaller
- Owner-occupancy: Not required. Pre-2025 local requirement removed to align with 760 CMR 71.00
- Short-term rental: Prohibited. Minimum 30-day rental term (local restriction allowed by state law)
- Same ownership: Main house and ADU must be owned by the same person. The ADU cannot be sold separately.
- Architectural continuity: Attached ADUs must maintain the architectural style of the main house to the extent possible
- Detached placement: Minimum 10 ft from the main house; located to the rear, or to the side at minimum 10 ft setback from the front plane of the main house
- Entrance and stairway: Restrictions apply on the location of ADU entrances and stairways to second-floor ADUs
- Parking: No additional parking within 0.5 miles of an MBTA stop (state law); one additional off-street space outside 0.5 miles
- Setbacks and dimensions: Per district under Section V-K and the zoning schedules. Confirm exact values with the Hingham Planning Department.
- Sewer status: Split. Coastal and central areas largely sewered, outlying areas septic
- Coastal flood zones: Hingham Harbor, Crow Point, Hingham Bay frontage, Weir River frontage
Why BuildX Knows Hingham ADUs
Hingham is part of BuildX's South Shore home territory. We work Hingham every month designing ADUs for your neighbors and know the coastal flood, historic-district, architectural-continuity, and septic constraints that drive your project.
We Work Hingham Every Month
Hingham is part of BuildX's South Shore home territory. We are your neighbors, not a regional contractor visiting Hingham. We work Hingham every month designing ADUs and know its parcels, overlays, sewer or septic status, and historic-district questions firsthand.
See One in Person
Walk through a real, finished BuildX ADU before you sign anything. Private showings are available by appointment.
Day 1 Property Review
Before quoting, we check zoning, sewer or septic, FEMA flood zone, wetlands, aquifer overlay, and historic district status.
BuildX on the South Shore
Hingham is part of BuildX's South Shore home territory. We work Hingham every month designing ADUs for your neighbors. We bid Hingham ADU projects regularly as part of our standard business operations. We don't have a Hingham build on the board yet. Yours could be the first.
What we've built nearby: the Williams ADU in Cohasset, which borders Hingham to the east, and the Rainis ADU in Norwell, just to the south, plus the Duggan ADU in Rockland. And across the South Shore, BuildX has an active pipeline of ADUs in two dozen towns, anchored by our flagship Plymouth portfolio, the most active ADU pipeline in the region.
Real families. Real builds. Real ADUs on the South Shore. See more BuildX ADU builds →
What Can Complicate a Hingham ADU?
Hingham is a coastal, historic, affluent town with a long ADU permit history. Your parcel's overlays and Hingham's local design standards, not the by-right bylaw, are usually what move project cost and timeline. The factors that come up most often:
Do I need septic approval for a Hingham ADU?
Likely affects you if: your parcel is in an inland or outlying Hingham neighborhood not connected to municipal sewer. Hingham has municipal sewer in some areas and private septic in others. Verify your specific parcel before you design.
Yes if your parcel is on private septic. Hingham is split: coastal and central areas such as Crow Point, the World's End vicinity, and the Hingham Square area are largely on municipal sewer, while many inland and outlying parcels are on private septic. Adding a bedroom adds wastewater design flow, so a Title 5 inspection and capacity check [Title 5] are typically required before the ADU permit is approved on a septic-served parcel.
Cost impact: $30,000 to $60,000 for a Title 5 capacity check plus possible system replacement when an older system cannot carry an additional ADU bedroom.
Confirm the exact municipal sewer boundaries for your street with the Hingham Building Department before design. We pull this on the Day 1 property review.
What flood-zone rules affect Hingham ADUs?
Likely affects you if: your parcel is along Hingham Harbor, Crow Point, Hingham Bay frontage, Weir River frontage, or any other coastal or low-lying parcel mapped in a FEMA flood zone.
Hingham has extensive coastal frontage along Hingham Harbor and Hingham Bay. Significant FEMA flood zones (Zone V and Zone A) run along Hingham Harbor, Crow Point, the Hingham Bay frontage, and the Weir River frontage. ADU projects on these parcels are different projects.
Cost premium: 15% to 25% on top of base ADU cost for elevation, breakaway walls, and engineer-stamped flood compliance.
Design requirements: FEMA-compliant elevation above base flood elevation, breakaway lower-level walls in V-zones, engineer-stamped structural design, and flood-resistant materials.
A waterfront Hingham ADU runs above standard build cost. We say that openly because it is real, and we want to set expectations on Day 1, not month 6. Engineer-stamped flood compliance is non-negotiable on the permit side.
Do historic district rules apply to Hingham ADUs?
Likely affects you if: your parcel sits inside the Hingham Square Historic District or near the Old Ship Meeting House area, or in any other parcel mapped in a Hingham Historic Districts Commission boundary.
Yes if your parcel is in a Hingham historic district. Hingham Square and the Old Ship Meeting House area are working historic districts. Old Ship Church (about 1681) is a National Historic Landmark and one of the oldest churches in continuous use in the United States. Hingham was settled in 1633.
- Local authority: Hingham Historic Districts Commission [Historic DC]
- Design review: Required for ADU projects in historic districts
- Cost premium: +10% to 15% when triggered
Detached ADUs in the historic districts face additional design review through the Hingham Historic Districts Commission. Massing, materials, fenestration, and roof form get scrutinized. The bylaw's architectural style-continuity requirement is enforced more closely in these character-heavy districts than in less historic parts of town. It adds time and cost. It is not a denial mechanism.
Do wetlands or conservation rules affect Hingham ADUs?
Likely affects you if: your lot is within 100 feet of any wetland, coastal resource area, pond, stream, or mapped wetland buffer zone. Hingham has extensive coastal and conservation frontage, so many parcels qualify.
Yes if your parcel falls within 100 feet of a wetland resource area. The Hingham Conservation Commission administers wetlands review under MGL c.131 §40 (the state Wetlands Protection Act) plus the local Hingham Wetlands Bylaw, which can extend regulatory jurisdiction beyond the state baseline. The state buffer is 100 feet from a wetland resource area.
Adding an ADU near a wetland resource area triggers a Notice of Intent or Request for Determination filing with the Conservation Commission. Plan on adding 30 to 90 days to the timeline if your parcel falls within the buffer.
Cost impact: +$5,000 to $15,000, plus 30 to 90 days of additional review.
Hingham carries significant conservation land, including World's End (a Trustees of Reservations peninsula on Hingham Bay), Wompatuck State Park (shared with Cohasset, Scituate, and Norwell), Bare Cove Park, and the Hingham portion of the Boston Harbor Islands. Parcels near these resource areas get closer Conservation Commission review.
How does the Hingham aquifer overlay affect ADUs?
Likely affects you if: your parcel falls within an aquifer or wellhead protection overlay tied to the Weir River Water System. These overlays apply to portions of town.
Hingham gets its water from the Weir River Water System, the regional system shared with Hull and Cohasset. Aquifer and wellhead protection overlays apply to portions of town. ADU septic siting near these overlays is reviewed more carefully.
Adding a bedroom adds wastewater design flow, and aquifer or wellhead overlays can limit how septic systems are sited and sized. A MassGIS overlay check on Day 1 tells you whether your parcel sits within one of these protection areas. We pull this before quoting.
Confirm the exact aquifer and wellhead overlay coverage for your parcel with the Hingham Planning Department or Building Department before design.
How do Hingham's three MBTA stops affect ADU parking?
Likely affects you if: your parcel is within 0.5 miles of West Hingham Station, Nantasket Junction, or the Hingham Shipyard ferry, or if your ADU adds bedrooms beyond the existing parking capacity.
Hingham is one of the most transit-served towns on the South Shore. It has three MBTA stops: two Greenbush Line commuter rail stations, West Hingham [MBTA WH] and Nantasket Junction [Greenbush], plus the Hingham Shipyard ferry to Boston [MBTA Ferry]. Together they create overlapping 0.5-mile parking-exemption zones across a substantial part of town.
Under state law (760 CMR 71.00) [760 CMR 71], no additional parking can be required for an ADU within 0.5 miles of an MBTA stop. Outside 0.5 miles, Hingham requires one additional off-street parking space.
We pull a transit-distance overlay on Day 1. Many Hingham parcels may qualify for the parking exemption from one or more of the three transit zones. Verify your parcel's distance by address before assuming the exemption applies.
What Does a Hingham ADU Cost?
A Hingham ADU should not be priced from square footage alone. Two 800 sq ft ADUs can price very differently depending on coastal flood elevation, historic-district design review, septic capacity, conservation review, and site access.
That is the full span of our 14 floor plans. Prices include the complete building package, foundation through move-in-ready finishes. Site work is priced separately after a lot evaluation.
Hingham-specific cost premium factors
See full ADU pricing and floor plans. For a Hingham-specific quote, call (781) 627-7000. We will not quote a Hingham ADU until we know your specific neighborhood, sewer or septic status, flood zone, historic-district status, and overlay status.
How the Hingham ADU Permit Process Works
One building permit, by-right. The work is in the clean package, not a special-permit hearing.
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1
Parcel review
1 to 2 weeks
BuildX maps your parcel against zoning, sewer or septic, FEMA flood zone, wetlands, aquifer overlay, historic district, and MBTA transit distance before quoting. This is the step that determines whether the rest of the timeline is straightforward or extended. MassGIS and parcel overlay checks happen on Day 1.
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2
Building permit application
Varies by completeness and town review queue, typically 60 to 120 days
Submit a complete application package to the Hingham Building Department: site plan with setbacks and dimensions; existing and proposed floor plans; architectural compatibility documentation for attached ADUs; and compliance with the detached placement rules. Approval is by-right (no special permit, no public hearing) for ADUs that meet Section V-K.
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3
Overlay reviews (if triggered)
Add 30 to 90+ days when triggered
Title 5 septic review (MassDEP 310 CMR 15.000) on septic parcels, Hingham Conservation Commission filing for the wetland buffer (MGL c.131 §40 plus the local Wetlands Bylaw), Hingham Historic Districts Commission design review for historic-district parcels, and FEMA flood compliance with engineer stamps for coastal parcels. These can run in parallel but extend the critical path.
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4
ZBA waiver (only if needed)
Case by case
For an ADU proposed within a lawfully existing nonconforming detached accessory structure, the Zoning Board of Appeals may waive setbacks to no less than 10 ft from a side or rear property line, on a finding of no unmitigatable negative visual or auditory impacts. This is a discretionary ZBA review, not the standard by-right ADU path. Confirm whether your project needs it with the Building Department.
Overall planning assumption: 60 to 120 days for the building permit on a clean parcel with no overlay triggers, faster than towns that require a special-permit hearing. Add 30 to 90+ days for any of the overlay reviews above.
After the permit issues, construction inspections run through the Hingham Building Department. Confirm current administrative posture at (781) 741-1420.
What Hingham Zoning Districts Allow ADUs?
ADUs are allowed by-right under Section V-K in Hingham's residential districts (the Residence A, Residence B, and Residence C single-family designations). ADUs are permitted on single-family lots in residential and mixed-use districts, not in standalone industrial or commercial districts. Hingham's bylaw is hosted as the 2025 clean copy; the exact per-district dimensional schedules (minimum lot, frontage, lot coverage, height) are confirmed with the Planning Department against Section V-K and the zoning schedules.
Residence districts (Residence A, B, C) Where ADUs are allowed
ADU rules: Detached, attached, and interior-conversion ADUs allowed by-right up to 900 sq ft or 50% of the main house gross floor area, whichever is smaller. One ADU per lot.
- Min lot: Per district under Section V-K and the zoning schedules. Confirm with the Hingham Planning Department.
- Min frontage: Per district. Confirm with the Hingham Planning Department.
- Max coverage: Per district. Confirm with the Hingham Planning Department.
- Max height: Per district. Confirm with the Hingham Planning Department.
- Setbacks: All front, side, and rear yard setbacks of the district must be met. ZBA waiver path to no less than 10 ft for nonconforming detached accessory structures.
What this means for your ADU: The by-right allowance is the same across the residential districts. What changes by parcel is the dimensional fit, the sewer or septic status, and whether an overlay (coastal flood, historic, aquifer, wetlands) applies. We confirm the exact district dimensions with the Planning Department and map your overlays before quoting.
Detached ADU placement rules
Hingham applies specific siting standards to detached ADUs under Section V-K:
- Distance from main house: Minimum 10 ft from the principal dwelling
- Location: To the rear of the principal dwelling, or to the side at a minimum 10 ft setback from the front plane of the principal dwelling
- Dimensional compliance: Must meet all front, side, and rear yard setbacks and the height limit of the district
Plan your site layout around these placement rules early. They affect where a detached ADU can sit on the lot more than the by-right allowance does.
Overlay districts. Aquifer, Floodplain, Historic.
Aquifer and wellhead protection overlays tied to the Weir River Water System, a Floodplain Overlay across FEMA-mapped coastal areas, and the Hingham Square and Old Ship Historic Districts. Overlays modify, but do not prevent, ADU construction.
Overlay analysis happens on Day 1 with MassGIS layers. We pull your parcel's overlays before quoting.
Source: Hingham Zoning By-Law, Section V-K (pages 136 to 138). Confirm exact dimensional values with the Hingham Planning Department.
Sewer or Septic? Hingham Is Split.
This is one of the biggest cost variables in a Hingham ADU project. Hingham has municipal sewer in some areas and private septic in others. Coastal and central areas such as Crow Point and the World's End vicinity are largely sewered; many inland and outlying parcels are on private septic. Verify your specific parcel before you design.
Show Title 5, water utility, and aquifer details
- Water utility: Weir River Water System (regional: Hingham, Hull, Cohasset)
- Septic upgrade cost: $30,000 to $60,000 typical where a Title 5 upgrade is needed
- Title 5 trigger: Adding a bedroom adds design flow, so Title 5 inspection required on septic parcels [Title 5]
- Aquifer: Aquifer and wellhead protection overlays apply to portions of town tied to the Weir River system
Coastal and central Hingham areas are largely sewered. Many inland and outlying parcels are on septic. We do not quote a Hingham ADU until we know which side of that line your parcel sits on. Confirm the exact municipal sewer boundaries with the Hingham Building Department; a Title 5 inspection answers the capacity question for your specific property.
Hingham Is Seven Markets in One
Hingham's neighborhoods have their own sewer status, flood-risk profile, and transit proximity. A Crow Point ADU is a different project from a South Hingham ADU. The MBTA proximity column matters here, because three in-town transit stops put many parcels inside a parking-exemption zone.
Hingham ADU Feasibility by Area (At a Glance)
| Hingham Area | Common ADU Issue | MBTA Proximity |
|---|---|---|
| Hingham Square / Town Center | Historic district, sewer access, design review | Close to West Hingham |
| West Hingham | Mixed sewer, Fort Hill Rd corridor | Within 0.5 mi of West Hingham station |
| Crow Point | Coastal flood exposure, sewered | Varies |
| Hingham Harbor / Shipyard | Coastal V-zone flood, waterfront | At the Hingham Shipyard ferry |
| Nantasket Junction area | Mixed sewer, moderate flood | Within 0.5 mi of Nantasket Junction |
| South Hingham | Likely septic, near Norwell and Rockland | Distant |
| The World's End vicinity is a conservation-adjacent coastal peninsula reviewed case by case. See the neighborhood card below for context. | ||
Hingham Square / Town Center Sewer
Historic colonial town center; the Old Ship Meeting House (about 1681) area; commercial and civic core; historic district. Design review applies to ADUs in the historic core.
Flood risk: Low to moderate. MBTA: Close to West Hingham station.
West Hingham Mixed
Around the West Hingham MBTA station along the Fort Hill Rd corridor. Mixed sewer and septic depending on parcel location.
Flood risk: Low. MBTA: Within 0.5 mi of the station, parking-exemption zone.
Crow Point Sewer High flood
Coastal peninsula, sewered, affluent. FEMA coastal flood exposure along the frontage.
Flood risk: High. Cost premium 15% to 25%.
Hingham Harbor / Shipyard Sewer High flood
Waterfront commercial and residential; the Hingham Shipyard ferry terminal and The Launch retail. FEMA V-zone exposure on waterfront parcels.
Flood risk: High (coastal V-zone). MBTA: At the Hingham Shipyard ferry to Boston.
Nantasket Junction area Mixed
Around the Nantasket Junction MBTA station. Mixed sewer and septic.
Flood risk: Low to moderate. MBTA: Within 0.5 mi of the station, parking-exemption zone.
South Hingham Septic
Inland southern Hingham near the Norwell and Rockland borders. Many parcels on private septic; Title 5 capacity is the gating issue.
Flood risk: Low. MBTA: Distant from the in-town stops.
World's End vicinity Sewer Coastal
Coastal peninsula adjacent to the Trustees of Reservations 251-acre property. Conservation-adjacent and affluent. Closer Conservation Commission review on parcels near the resource area.
Flood risk: Moderate (coastal). MBTA: Distant.
Hingham Building Department
Hingham Building Department
- AddressHingham Town Hall, 210 Central Street, Hingham, MA 02043
- Phone(781) 741-1420 (press 1 for the Building Commissioner)
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Hours (effective July 1, 2024)
Monday7:00 AM to 5:00 PMTuesday7:00 AM to 7:00 PMWednesday7:00 AM to 5:00 PMThursday7:00 AM to 5:00 PMFridayClosed
- Building CommissionerMichael J. Clancy, CBO [Hingham BD]. Office hours: Monday to Thursday 7:00 to 10:00 AM; Tuesday 4:00 to 6:00 PM.
- Conservation AgentAbby Piersall [Conservation], under the Community Planning Department, for wetland-buffer questions.
- ZBA (plan-confirmation)(781) 804-2315 for ADU plan-confirmation and setback-waiver questions.
- Online permittingOnline permitting software, linked from the Town's Building page.
- Building Departmenthingham-ma.gov/207/Building
- Town ADU pagehingham-ma.gov/1090/Accessory-Dwelling-Units
Hingham's Building Department opens at 7:00 AM and stays open until 7:00 PM on Tuesdays, which is unusual for a Massachusetts building department and worth using for evening conversations. The Friday closure is the trade-off. Building Commissioner Clancy keeps documented early-morning office hours.
Questions to ask when you call Hingham
- Is my parcel in a residential district where ADUs are allowed by-right under Section V-K?
- Is my property sewered or on septic, and will Title 5 review be required?
- Is my parcel in a FEMA flood zone, a historic district, a wetland buffer, or an aquifer or wellhead overlay?
- How is the architectural style-continuity requirement enforced for my project?
- Does my parcel qualify for the parking exemption within 0.5 miles of an MBTA stop?
- Do I need a ZBA setback waiver for a nonconforming detached accessory structure?
Explore Hingham ADU Topics
Jump to the deep-dive sections on this page for the detail behind each Hingham ADU topic.
Hingham ADU FAQs
Can I build a detached ADU in Hingham?
Yes, by-right. Hingham amended Section V-K of the Zoning By-Law at the April 28-29, 2025 Annual Town Meeting to comply with the Affordable Homes Act, and the Attorney General's Office approved it. Detached, attached, and interior-conversion ADUs are all permitted by-right with a building permit in Hingham's residential districts, up to 900 square feet or half the main house gross floor area, whichever is smaller. Detached ADUs must sit at least 10 ft from the main house and follow the placement rules.
Do I need a special permit for a Hingham ADU?
No. The April 2025 amendment removed the older special-permit requirement. A compliant ADU under Section V-K is allowed by-right with a single building permit, with no special permit and no public hearing. The work is in the design standards and overlay reviews, not a hearing.
Do I need to live there?
No. Hingham's pre-2025 bylaw required owner-occupancy, but state law (760 CMR 71.00) preempts owner-occupancy requirements for protected-use ADUs, and the April 2025 amendment removed that requirement. In practice, you may rent the principal dwelling and live in the ADU, or live in the principal dwelling and rent the ADU. Some older online sources still reference the outdated rule. Confirm current operating posture with the Hingham Building Department at (781) 741-1420 before signing a lease.
Can I Airbnb my Hingham ADU?
No. Hingham requires a minimum 30-day rental term, which effectively bans short-term rentals such as Airbnb and VRBO while permitting all longer-term housing. State law allows local short-term rental restrictions, so Hingham's rule is enforceable. If your business model is short-term rental income, Hingham is not your town. Long-term rentals, in-law, and caregiver housing are fine.
Can I sell the ADU separately?
No. Hingham's bylaw requires the main house and the ADU to be owned by the same person or persons. The ADU cannot be sold as a separate unit. It stays part of the same property.
How big can a Hingham ADU be?
Up to 900 square feet, or up to half the principal home's gross floor area, whichever is smaller. This matches the state by-right cap under 760 CMR 71.00, so Hingham's local rule and state law align on size.
What if my house is in a historic district?
You can still build, but additional design review applies. Detached ADUs in the Hingham Square or Old Ship Historic Districts go through the Hingham Historic Districts Commission, which scrutinizes massing, materials, fenestration, and roof form. The bylaw's architectural style-continuity requirement is enforced more closely here. Plan for added time and roughly 10% to 15% added cost when historic review is triggered.
Will I need an extra parking space?
It depends on transit distance. Within 0.5 miles of any of Hingham's three MBTA stops (West Hingham, Nantasket Junction, or the Hingham Shipyard ferry), no additional parking can be required under state law (760 CMR 71.00). Outside 0.5 miles, Hingham requires one additional off-street parking space. Verify your parcel's distance by address before assuming the exemption applies.
What does a Hingham ADU cost?
BuildX ADU pricing ranges from $284,301 to $525,861. That covers the complete building package, foundation through move-in-ready finishes; site work is priced separately after a lot evaluation. Hingham-specific drivers move a project within and beyond that band: coastal flood zone parcels (Hingham Harbor, Crow Point, Bay frontage) add 15% to 25% for elevation, breakaway walls, and engineer-stamped flood compliance. Historic district parcels add 10% to 15% for design review. Septic upgrades add $30,000 to $60,000 where a Title 5 upgrade is needed. For a property-specific quote, call (781) 627-7000.
How long does a Hingham ADU permit take?
Plan on 60 to 120 days for the by-right building permit on a clean parcel, faster than towns that require a special-permit hearing. Add 30 to 90 days for any of: Title 5 septic review, Conservation Commission filing within a wetland buffer (100 ft under MGL c.131 §40 and the local Wetlands Bylaw), Hingham Historic Districts Commission review, or FEMA flood-zone compliance on coastal parcels.
Who do I call about building an ADU in Hingham?
For official town process questions (permits, fees, inspector availability, building code interpretation), call the Hingham Building Department at (781) 741-1420 and press 1 for the Building Commissioner.
For parcel-level feasibility, cost estimates, design options, neighborhood-specific considerations, and construction planning, call BuildX at (781) 627-7000.
The two are different conversations. The town can tell you what is administratively required. BuildX can tell you what is realistic on your specific parcel and what it will actually cost to build.
Can I build an ADU on septic in Hingham?
Possibly. The existing septic system must have capacity under Title 5 (Massachusetts state regulations on subsurface sewage disposal, 310 CMR 15.000) to handle the additional bedroom that an ADU typically adds. Adding a bedroom adds wastewater design flow, and Title 5 calculates whether the system can carry it.
Many inland and outlying Hingham parcels rely on private septic, while coastal and central areas are largely sewered. If your existing system lacks capacity, an upgrade or full replacement adds $30,000 to $60,000 or more to the project cost. The first thing BuildX does on a Hingham septic property is assess Title 5 capacity before any design work begins, as part of the Property Review.
Sources Reviewed
Last verified: September 20, 2026. Grouped by source type so you can see which claims come from town law, state law, town process, local constraints, and media records.
View all 20 sources, grouped
- Town of Hingham. Hingham Zoning By-Law (2025 Clean Copy). Section V-K (Accessory Dwelling Units), pages 136 to 138, as amended through the April 28-29, 2025 Annual Town Meeting.
- Town of Hingham. Accessory Dwelling Units. Town's homeowner-facing ADU information page.
- Town of Hingham. ADU Planning Documents Library. Annual Town Meeting amendment supporting documents.
- Town of Hingham. Proposed By-Law Amendments. April 28-29, 2025 ATM Section V-K amendment trail.
- Commonwealth of Massachusetts. Accessory Dwelling Units (760 CMR 71.00). State ADU regulations; protected-use definition and parking exemption.
- Massachusetts General Laws. M.G.L. Chapter 40A §§1A and 3A; Chapter 150 of the Acts of 2024 §8. Affordable Homes Act ADU provisions.
- MassDEP. Title 5 (310 CMR 15.000) Compliance for ADUs FAQ.
- Town of Hingham. Hingham Building Department. Building Commissioner Michael J. Clancy, office hours, contact, and online permitting.
- Town of Hingham. Hingham Conservation Commission (Community Planning Department). Conservation Agent Abby Piersall; wetlands review under MGL c.131 §40 and the local Wetlands Bylaw.
- Town of Hingham. Hingham Historic Districts Commission. Historic district design review for ADU projects in the Hingham Square and Old Ship districts.
- Town of Hingham. Transportation Information. Transit access from the Town's perspective.
- Hingham Affordable Housing Trust. Affordable housing context and ADU advocacy (use cautiously for general context).
- MBTA. West Hingham Station (Greenbush Line). In-town commuter rail station at 20 Fort Hill Rd.
- MBTA. Hingham Ferry to Boston (Boat-Hingham). Hingham Shipyard ferry terminal at 28 Shipyard Dr.
- MBTA. Greenbush Commuter Rail Line. Greenbush Line context, including the Nantasket Junction stop in Hingham.
- U.S. Census 2020. Hingham, MA. Population, area, geography, and history.
- Census Reporter. Hingham Town Profile. Demographics, including median household income.
- Hingham Unity Council. ADU FAQ. Local community context (use cautiously for general context).
- Town of Hingham. Hingham Center for Active Living (Senior Center). Aging-in-place housing context.
- Boston Globe. Modular ADU industry coverage. December 1, 2025. South Shore ADU industry-trend signal: local builders report building roughly twice as many ADUs since the state law took effect.
Nearby South Shore ADU Rules
Hingham borders Cohasset to the east (sharing the Weir River Water System), Scituate to the southeast, Norwell to the south, and Weymouth to the west. All four are home territory for BuildX, the same South Shore neighborhoods we work every month.
ADU Rules by City in the BuildX Service Area
BuildX serves 40 towns across four areas of southeastern Massachusetts. Each city has its own ADU bylaw, sewer or septic split, overlay map, and Building Department contact. Jump to the rules for your town:
South Shore (22)
South Coast (9)
Bridgewater Area (5)
Thinking about an ADU in Hingham?
BuildX can review your Hingham parcel for zoning, sewer or septic, FEMA flood zone, wetlands, aquifer overlay, historic-district status, and MBTA parking-exemption distance before you spend money on design or permitting. Hingham is BuildX home territory, so we know the constraints that drive your project and the by-right path through Section V-K.
See our ADU project portfolio or visit the ADU Home TourDisclaimer: The information on this page is drawn from live interviews, podcast episodes, municipal bylaws, planning board materials, town websites, and other publicly available sources, and reflects what was accurate as of the original recording or verification date. Pricing, timelines, materials, regulations, zoning rules, permit processes, fees, and overlay district boundaries can change -- sometimes without public notice -- and no two towns interpret or apply the rules the same way. This page is for informational purposes only and should not be relied upon as the basis for any purchasing, construction, or investment decision. BuildX makes no guarantee that the information is current or complete for your specific parcel. Before making any decisions, contact the town directly or call BuildX at (781) 627-7000 or schedule a Project Clarity Call to review your specific situation.