Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Quincy ADU cost →Building an ADU in Quincy costs between $220,000-$400,000 for new construction, with per-square-foot costs averaging $275-$450. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $100,000-$250,000, while prefab/modular ADUs fall in between at $250,000-$480,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & 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). |
| Site Prep & Foundation | $10,000 – $35,000 |
| Framing & Structure | $15,000 – $45,000 |
| Plumbing | $8,000 – $20,000 |
| Electrical | $5,000 – $15,000 |
| HVAC | $3,000 – $8,000 |
| Interior Finishes | $15,000 – $40,000 |
Quotes for the same ADU commonly vary 20–40% between builders. We pass your request to up to 5 local builders serving Quincy, where we have them — free, no obligation.
Get Quincy builder quotes →Permit fees in Quincy are 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.. The review timeline is 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., with 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.. Impact fees are 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).. 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..
| 1-Bedroom Rent | $2,250-$2,650/month |
| 2-Bedroom Rent | $2,650-$3,150/month |
| Annual Rental Income (est.) | $29,400/year |
| Payback Period (est.) | 10.5 years |
| 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. |
| Overall ROI Estimate | 7-14% gross rent yield (estimate) |
A typical ADU in Quincy generates approximately $29,400 per year in rental income based on average 1-bedroom rents. At an average construction cost of $310,000, the estimated payback period is 10.5 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Quincy and varies by market (often less than build cost).
1. Garage conversions save 40-60% vs new construction since the shell already exists. Average cost in Quincy: $100,000-$250,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $250,000-$480,000.
3. Pre-approved plans — available in Quincy, which can save $3,000-$10,000 in design costs and 2-3 months in review time. See which cities offer pre-approved ADU plans.
4. State grants — California's CalHFA ADU grant (up to $40K) is currently paused; check calhfa.ca.gov/adu for status and your state for active programs.
5. Get multiple bids — ADU contractor pricing varies 20-40% for the same project. We recommend getting at least 3 quotes.
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