Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Medford ADU cost →Building an ADU in Medford 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-$525,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | $15.00 per $1,000 of estimated construction cost plus a $35.00 application fee, a $100.00 plan review fee for 1-4 family dwellings and $125.00 for a certificate of occupancy (Schedule of Building Fees effective July 28, 2009; Code Appendix A, § 10-35) — about $3,885 on a $250,000 ADU. |
| Impact Fees | None for a by-right ADU. 760 CMR 71.03(3)(b)(6) bars any impact fee or study not required of a single-family house in the same district. Medford's development linkage fees (§ 94-10.1.2) apply only to a "development impact project": nonresidential development of 10,000 sq ft or more, a residential structure of six or more units, a subdivision creating six or more units or lots, or a project of 5,000 sq ft or more that needs a density bonus, variance, special permit or map amendment. One ADU meets none of these. |
| 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 Medford, where we have them — free, no obligation.
Get Medford builder quotes →Permit fees in Medford are $15.00 per $1,000 of estimated construction cost plus a $35.00 application fee, a $100.00 plan review fee for 1-4 family dwellings and $125.00 for a certificate of occupancy (Schedule of Building Fees effective July 28, 2009; Code Appendix A, § 10-35) — about $3,885 on a $250,000 ADU.. The review timeline is The Building Department's FAQ says the building official has 30 days to review and act on a building permit application and that most reviews finish sooner; new buildings go to the weekly Tuesday development meeting for multi-department sign-off. No ADU-specific timeline is published., with plan check: Standard building plan review ($100.00 plan review fee, 1-4 family dwellings). Two Massachusetts items to settle early: Title 5 — if the lot is on septic, 310 CMR 15.000 applies through the Board of Health and the § 94-8.2.3(1) plot plan must show the system; and utilities — 760 CMR 71.03(3)(b)(3) says the city may not require a separate water, sewer or electric connection, though the utility or a state board still can. Work started without a permit is charged a quadruple fee (Appendix A, § 10-35(10)). Every ADU must be assigned an address to the MassGIS standard and reported to MassGIS and EOHLC (760 CMR 71.03(8)).. Impact fees are None for a by-right ADU. 760 CMR 71.03(3)(b)(6) bars any impact fee or study not required of a single-family house in the same district. Medford's development linkage fees (§ 94-10.1.2) apply only to a "development impact project": nonresidential development of 10,000 sq ft or more, a residential structure of six or more units, a subdivision creating six or more units or lots, or a project of 5,000 sq ft or more that needs a density bonus, variance, special permit or map amendment. One ADU meets none of these.. Pre-approved plans: None from the City of Medford — no plan gallery appears on the Building Department or Planning pages as of September 20, 2026. EOHLC's Accessory Dwelling Units page on mass.gov is the state's ADU resource hub; check it for plan and financing material before commissioning a custom set..
| 1-Bedroom Rent | $2,500-$2,800/month |
| 2-Bedroom Rent | $3,000-$3,350/month |
| Annual Rental Income (est.) | $31,800/year |
| Payback Period (est.) | 9.7 years |
| Short-Term Rental | No — 30-day minimum rental term for the ADU or the house (§ 94-8.2.3(6)); state law lets a city restrict short-term rental of an ADU (M.G.L. c. 40A § 3; 760 CMR 71.03(3)(c)). Long-term letting of both units is allowed. |
| Overall ROI Estimate | 6-10% net annual yield (estimate: $220,000-$400,000 build, $2,500-$3,350/mo HUD-based rent, before financing) |
A typical ADU in Medford generates approximately $31,800 per year in rental income based on average 1-bedroom rents. At an average construction cost of $310,000, the estimated payback period is 9.7 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Medford 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 Medford: $100,000-$250,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $250,000-$525,000.
3. Pre-approved plans — Medford does not offer a pre-approved/standard ADU plan program yet, so budget for custom architectural plans (typically $3,000-$15,000). 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.
Tell us about your project and we'll pass it to ADU builders serving Medford. Free, no obligation — you choose who to work with. We don't have builders in every area yet; if nobody covers yours, we'll email you to say so.
🔒 Your info is secure. We share it only with contractors quoting your project. No spam, no obligation.
Just browsing? Search ADU builders near you by ZIP code.