Yes. Since the state ADU law (M.G.L. c. 40A §3, Ch. 150 of 2024 §8; 760 CMR 71.00, effective Feb 2, 2025) Quincy allows one ADU by right on any lot in a single-family zoning district, inside the house, as an addition, or detached, with a building permit from Inspectional Services and no hearing. Quincy has not written an ADU section into the Zoning Ordinance (Chapter 375); it applies the state rules through ISD's Accessory Dwelling Unit Guidelines (December 11, 2025). Those cap the unit at 900 sq ft or 50% of the house's gross floor area, whichever is less, set a 320 sq ft minimum for a detached unit, limit detached units to one story and to the principal-building yards in QZO Table 4.1 (Residence A: 25 ft front, 13 ft side, 20 ft rear), bar ADUs in Bus C, Ind A and Ind B districts, on lots subject to a variance and below the FEMA 100-year base flood elevation, and prohibit short-term rental. No owner-occupancy requirement and no parking space within half a mile of a transit station.
Zoning & Size Requirements [1][2][3][4][5][6][7][8][9]
Yes — Quincy allows ADUs. A detached ADU can typically be up to 900 sq ft under current Massachusetts and Quincy zoning rules.
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| Allowed Zones | One ADU by right (no special permit or variance) on any lot in a district where single-family homes are allowed, i.e. Residence A and B (760 CMR 71.02-71.03; ISD Guidelines Dec 11, 2025) — within the dwelling, as an addition, or detached. Not allowed in Bus C, Ind A or Ind B districts, or on a lot subject to a variance. QZO Chapter 375 has no ADU section; the state law and the ISD guidelines govern. |
| Max Size (Detached) | 900 sq ft or 50% of the principal dwelling's gross floor area, whichever is less (760 CMR 71.02, applied by the ISD guideline). Minimum 320 sq ft for a detached ADU — a local ISD figure, not a state or 780 CMR rule. Example: a 1,500 sq ft house allows 750 sq ft; 1,800 sq ft or larger allows the full 900. |
| Max Size (Attached) | Same cap as detached: 900 sq ft or 50% of the principal dwelling's gross floor area, whichever is less (760 CMR 71.02). No minimum size is stated for an internal or attached ADU. |
| Max Size (JADU) | No JADU category in Massachusetts law — an internal unit is simply an ADU under the same 900 sq ft / 50% cap |
| Max Height | Detached ADU limited to one story (ISD guideline). District caps in QZO Table 4.1: Residence A 2.5 stories, Residence B 3 stories; a garage as an accessory building is capped at 16 ft (§375-3.2.3.1). An internal or attached ADU follows the principal building's limit. |
| Max Units | 1 ADU per lot (ISD guideline; 760 CMR 71.02 protects only one ADU per lot). Not counted toward density (71.03(2)(d)). No separate ownership, and no ADU below the FEMA 100-year base flood elevation on the FEMA Flood Hazard Map for Quincy. |
Setback Requirements [1][2][3][4][5][6][7][8][9]
Quincy requires a rear setback of about 20 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | Detached ADU must meet the principal-building yards in QZO Table 4.1 (ISD guideline): Residence A 20 ft rear; Residence B (1-3 units) 25 ft rear; Residence C half the building height, never less than 25 ft. Note: a garage or shed may sit 6 ft from the rear line (§375-3.2.3.1) and 760 CMR 71.03(3)(b)2 bars ADU dimensional rules stricter than those for an accessory structure — ask ISD in writing which figure it will apply. |
| Side Setback | Per QZO Table 4.1 (ISD guideline): Residence A 13 ft; Residence B (1-3 units) 13 ft; Residence C half the building height, minimum 25 ft. Accessory buildings (garages, sheds) are otherwise allowed 6 ft from a side line (§375-3.2.3.1); see the 760 CMR 71.03(3)(b)2 note under rear setbacks. |
| Front Setback | Per QZO Table 4.1: 25 ft in Residence A and B. In Residence A the building must also match the average front setback of houses within 300 ft on the same side of the street, never less than 25 ft or more than 55 ft (Table 4.1 note 1). Residence C: half the building height, minimum 25 ft. |
| Parking Required | None if the ADU is within 0.5 mile of a Transit Station (760 CMR 71.02 counts subway, commuter rail, ferry and MBTA bus stops — Quincy has four Red Line stations); otherwise 1 additional off-street space (ISD guideline; state max). Existing off-street parking may not be removed to create the ADU and must comply with QZO §375-5.1: in Residence A/B, spaces 3 ft from side and rear lines, no enclosed parking in the front yard, driveway max 20 ft wide. |
| Owner Occupancy | Not required — 760 CMR 71.03(2)(a) bars any owner-occupancy condition on a Protected Use ADU and Quincy's guidelines impose none. The ADU may not be sold or owned separately from the house (ISD guideline: 'ADUs shall not have separate ownership'). |
| Min Lot Size | None — 760 CMR 71.03(3)(b)2 bars a minimum lot size for a Protected Use ADU, and 71.02 protects a principal dwelling 'regardless of whether it, or the Lot it is situated on, conforms to Zoning'. District minimums (Residence A 7,650 sq ft, Residence B 6,750 sq ft, Table 4.1) do not block an ADU on an existing undersized lot. |
Permit Process & Fees [10][11][12][13]
An ADU permit in Quincy goes through a ministerial, by-right review. Review time: not published — Quincy ISD does not post building-permit review times; 760 CMR 71.03(1) requires an as-of-right review with no hearing or discretionary approval. Confirm the current queue with Inspectional Services. Permit fees: Valuation-based building permit fee under Municipal Code Ch. 150 Art. III (Inspectional Services fees); no ADU-specific fee is published. Confirm the current figure with ISD (617-376-1450) before budgeting.
| Approval Process | By-right building permit from Inspectional Services (1305 Hancock St; permits 617-376-1450), filed as the 'Accessory Dwelling Unit Application' on ViewPoint Cloud. Submit a site plan showing drainage, utilities and existing/proposed parking plus architectural drawings; comply with 780 CMR, 527 CMR 18 fire access (detached units), the state plumbing code, Quincy DPW utility rules and QZO §375-3.4 (no new nonconformity). Free building/zoning clinics Thursdays 2-4 pm at ISD, 55 Sea St. |
| Review Timeline | Not published — Quincy ISD does not post building-permit review times; 760 CMR 71.03(1) requires an as-of-right review with no hearing or discretionary approval. Confirm the current queue with Inspectional Services. |
| Permit Fees | Valuation-based building permit fee under Municipal Code Ch. 150 Art. III (Inspectional Services fees); no ADU-specific fee is published. Confirm the current figure with ISD (617-376-1450) before budgeting. |
| Impact Fees | None — Quincy charges no development impact fee for a single ADU, and 760 CMR 71.03(3)(b)6 bars any fee or study not required for a single-family house. A separate water/sewer connection (and its DPW charge) can be required only if the utility requires it (71.03(3)(b)3). |
| Plan Check | ISD reviews the site plan (drainage, utilities, parking) and architectural drawings against 780 CMR and the guidelines, screens the parcel against the FEMA 100-year Flood Hazard Map (no ADU below base flood elevation) and the QZO §8.1 Floodplain Overlay District; the Conservation Commission reviews construction in flood plain areas and near wetlands. |
| Pre-Approved Plans | None — Quincy publishes no pre-approved or pre-reviewed ADU plan set; ISD's 'Helpful Forms and Checklists' list only the ADU guidelines and the Table of Dimensional Requirements. |
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Construction Costs [14][15][16]
Building an ADU in Quincy typically costs $220,000-$400,000 ($275-$450 per sq ft); a garage conversion runs $100,000-$250,000.
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| Average Build Cost | $220,000-$400,000 |
| Cost per Sq Ft | $275-$450 |
| Garage Conversion | $100,000-$250,000 |
| Prefab ADU (Installed) | $250,000-$480,000 |
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Rental Income Potential [17][18]
A 2-bedroom ADU in Quincy rents for around $2,650-$3,150/mo, an estimated 7-14% gross rent yield (estimate).
| Avg Rent (1 Bedroom) | $2,250-$2,650/mo |
| Avg Rent (2 Bedroom) | $2,650-$3,150/mo |
| Short-Term Rental | No — the ISD ADU guidelines bar using an ADU as a short-term rental (permitted by 760 CMR 71.03(3)(c)), and Municipal Code §196-14 (Order 2020-125, adopted Mar 15, 2021) limits short-term rentals (under 31 days) to the o. |
| Est. Annual ROI | 7-14% gross rent yield (estimate) |
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Recent Law Changes
What's Changed Recently
- Sep 20, 2026 — Entry re-verified against QZO Chapter 375 (§§3.2, 3.4, 4.1, 5.1), the ISD ADU Guidelines (Dec 11, 2025), Municipal Code §196-14 and 760 CMR 71; Table 4.1 setback figures added, rents moved to HUD FY2027 SAFMRs, costs re-based on 2026 Massachusetts guides
- Dec 11, 2025 — Quincy ISD republished its ADU Guidelines: state 900 sq ft / 50% cap, 320 sq ft detached minimum, one-story detached limit, Table 4.1 yards, FEMA flood bar, no separate ownership, no short-term rental
- 2025 — No local ADU ordinance: the Council's 2025 zoning orders (2025-027 Floodplain Overlay rewrite, 2025-058 Transit-Oriented Districts) added no ADU section to Chapter 375; the state law applies directly through the ISD guidelines
- Feb 2, 2025 — Ch. 150 of 2024 §8 (M.G.L. c. 40A §3) and 760 CMR 71.00 took effect: one ADU by right in single-family districts, no owner-occupancy condition, parking capped at 1 space and none within 0.5 mile of transit
Tips for Building an ADU in Quincy
- Settle the detached-unit setback before you design: ISD's guideline asks for the full Table 4.1 yards (13 ft side, 20-25 ft rear), but QZO §375-3.2.3.1 allows a garage 6 ft from side and rear lines and 760 CMR 71.03(3)(b)2 says ADU dimensional rules may be no stricter than those for an accessory structure — get ISD's answer in writing
- Size math: 900 sq ft or half the house's gross floor area, whichever is smaller (760 CMR 71.02) — a 1,400 sq ft house allows 700 sq ft, 1,800 sq ft or more allows 900; a detached unit must be at least 320 sq ft
- Check the FEMA Flood Insurance Rate Map for your parcel first: no ADU may sit below the 100-year base flood elevation, and Order 2025-027 (filed Mar 3, 2025) proposed requiring a special permit for any new building in the QZO §8.1 Floodplain Overlay District — ask ISD whether it was adopted
- Within 0.5 mile of North Quincy, Wollaston, Quincy Center or Quincy Adams (Red Line), Quincy Center commuter rail, or an MBTA bus stop, no parking space can be required (760 CMR 71.02 'Transit Station' includes bus stations); elsewhere it is 1 space, and you cannot remove an existing space to fit the unit
- If your house already breaks a setback or lot rule, §375-3.4.5 lets the ISD Director approve an addition that does not increase the nonconformity; a new or larger nonconformity needs a ZBA variance (§375-3.4.4), and the guideline excludes lots that are 'subject to a variance'
- Don't plan on Airbnb income: the guidelines bar short-term rental of an ADU and §196-14 bars all short-term rentals in Residence A — underwrite with long-term rents (HUD FY2027 SAFMR 1BR: 02169 $2,570, 02170 $2,230, 02171 $2,650)
- Cost basis: 2026 Massachusetts guides put a detached 800-900 sq ft stick-built ADU at $220,000-$400,000 ($275-$450 per sq ft), a garage or basement conversion at $100,000-$250,000 and a 650-750 sq ft prefab installed in Greater Boston at $250,000-$480,000; site work, frost-depth foundations and DPW utility connections are the swing items
- Parking layout in Residence A/B follows §375-5.1.4: spaces at least 3 ft from other lot lines, no enclosed parking in the front yard, driveway no wider than 20 ft and no more than 30% of the front yard, rear-yard paving capped at 40%
- Bring your sketch to ISD's free Building, Zoning and Conservation clinic (Thursdays 2-4 pm, 55 Sea St, no appointment) before paying for drawings — staff will flag flood, setback and utility issues on the spot
- Cost basis (2026-09-20 re-verification): short term allowed: No — the ISD ADU guidelines bar using an ADU as a short-term rental (permitted by 760 CMR 71.03(3)(c)), and Municipal Code §196-14 (Order 2020-125, adopted Mar 15, 2021) limits short-term rentals (under 31 days) to the operator's primary residence, bars them entirely in Residence A, requires annual ISD registration and fines $100 per day.
ADU Builders in Quincy
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Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Accessory Dwelling Units — Guidelines December 11, 2025 (Quincy Inspectional Services; read via the Wayback Machine capture of Dec 24, 2025 — quincyma.gov returns 403) Planning Department — Accessed 2026-09-20
- Dimensional Regulations — Table of Dimensional Requirements handout (Quincy ISD, 2024; QZO §4.1) Planning Department — Accessed 2026-09-20
- Quincy Zoning Ordinance Chapter 375 §4.1 Table of Dimensional Requirements (eCode360) Municipal Code — Accessed 2026-09-20
- Quincy Zoning Ordinance Chapter 375 §3.2 Accessory uses and structures (eCode360) Municipal Code — Accessed 2026-09-20
- Quincy Zoning Ordinance Chapter 375 §3.4 Nonconforming uses and structures (eCode360) Municipal Code — Accessed 2026-09-20
- Quincy Zoning Ordinance Chapter 375 §5.1 Off-street parking (eCode360) Municipal Code — Accessed 2026-09-20
- 760 CMR 71.02 Definitions (Accessory Dwelling Unit, Principal Dwelling, Protected Use ADU, Transit Station) state_statute — Accessed 2026-09-20
- 760 CMR 71.03 Regulation of Protected Use ADUs in Single-family Residential Zoning Districts state_statute — Accessed 2026-09-20
- Accessory Dwelling Units — Mass.gov (EOHLC) state_statute — Accessed 2026-07-10
- Online Applications List — Quincy Inspectional Services (ViewPoint Cloud ADU application) building_dept — Accessed 2026-09-20
- Building Department — Quincy Inspectional Services (clinics, forms and checklists) building_dept — Accessed 2026-09-20
- Ordinance Committee agenda May 5, 2025 — Order 2025-027, Amendment to Zoning Code Section 8.1 Floodplain Overlay District ordinance — Accessed 2026-09-20
- Quincy City Council agenda June 16, 2025 (2025-058 Transit-Oriented Districts; no ADU ordinance) ordinance — Accessed 2026-09-20
- Dwelly, How Much Does an ADU Cost in Massachusetts in 2026? (Mar 7, 2026) industry — Accessed 2026-09-20
- Horizon ADU, How Much Does a 900 Sq Ft ADU Cost in Massachusetts? (Jul 24, 2026) industry — Accessed 2026-09-20
- ADU Wizard, How Much Does an ADU Cost in Massachusetts in 2026? industry — Accessed 2026-09-20
- HUD FY2027 Small Area Fair Market Rent Schedule (Boston-Cambridge-Quincy HMFA: ZIPs 02169, 02170, 02171) Government Data — Accessed 2026-09-20
- Municipal Code §196-14 Regulation of short-term residential rentals (Order 2020-125, added 3-15-2021) ordinance — Accessed 2026-09-20
Frequently Asked Questions
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