Complete 2026 cost breakdown: construction, permits, financing, and expected rental ROI.
Calculate your Durham ADU cost →Building an ADU in Durham costs between $150,000-$400,000 for new construction, with per-square-foot costs averaging $250-$400+. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $65,000-$140,000, while prefab/modular ADUs fall in between at $80,000-$137,000.
| Cost Category | Estimated Range |
|---|---|
| Architectural Plans | $3,000 – $15,000 |
| Permits & Fees | Building & Safety schedule (effective 7/1/2018, still the posted schedule): new dwelling up to 1,200 sq ft $146 building permit + $146 plan review; electrical 100-200 amp service $156; mechanical heating/cooling system $125; plumbing for a new dwelling $170; Homeowner's Recovery Fund $10. Plus Planning review of the building permit $110 and Infrastructure Residential Building Permit Review $436.80 (Development Services fee menu, July 2026). About $1,300 in City fees for a new detached unit; a conversion or addition is priced as a residential addition/renovation ($125-$250 permit + $125 plan review, plus trade permits). |
| Impact Fees | Street impact fee per ADU: $293 Downtown, $531 North, $1,405 South (City Fee Schedule Part 4-112 tables, 2009 rates still posted by Building & Safety); ask whether the parks ($425/unit) and open-space ($222/unit) impact fees are also charged. Water and sewer capital facility fees apply to a new connection: $5,619 for a 5/8-inch meter (water $2,591 + sewer $3,028; Reference Guide for Development Sec. 13.1.E, in force since Jan 1, 2024) plus a $721 City meter set. The plot-plan checklist lets an ADU share the house's sewer service and meter, with a second meter optional for separate billing; confirm with Public Works Engineering (919-560-4326) whether any capital facility fee is assessed when no new tap is made. |
| 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 Durham, where we have them — free, no obligation.
Get Durham builder quotes →Permit fees in Durham are Building & Safety schedule (effective 7/1/2018, still the posted schedule): new dwelling up to 1,200 sq ft $146 building permit + $146 plan review; electrical 100-200 amp service $156; mechanical heating/cooling system $125; plumbing for a new dwelling $170; Homeowner's Recovery Fund $10. Plus Planning review of the building permit $110 and Infrastructure Residential Building Permit Review $436.80 (Development Services fee menu, July 2026). About $1,300 in City fees for a new detached unit; a conversion or addition is priced as a residential addition/renovation ($125-$250 permit + $125 plan review, plus trade permits).. The review timeline is No turnaround time is published. The plan-review fee is paid at submittal and status is tracked in Dplans / LDO; the first re-review is free, the second costs $200; an application with no activity for six months is voided and the plan-review fee is forfeited., with plan check: Digital plan review through Dplans: drawings split by trade as flattened PDFs under 200 MB, plan-review fee credited against the permit fee at issuance, sealed plot plan required for any new or changed footprint. An optional Enhanced Plan Review (face-to-face, $600 per hour) is available after one standard review round.. Impact fees are Street impact fee per ADU: $293 Downtown, $531 North, $1,405 South (City Fee Schedule Part 4-112 tables, 2009 rates still posted by Building & Safety); ask whether the parks ($425/unit) and open-space ($222/unit) impact fees are also charged. Water and sewer capital facility fees apply to a new connection: $5,619 for a 5/8-inch meter (water $2,591 + sewer $3,028; Reference Guide for Development Sec. 13.1.E, in force since Jan 1, 2024) plus a $721 City meter set. The plot-plan checklist lets an ADU share the house's sewer service and meter, with a second meter optional for separate billing; confirm with Public Works Engineering (919-560-4326) whether any capital facility fee is assessed when no new tap is made.. Pre-approved plans: None. The City's Affordable ADU Pilot Program (Housing & Neighborhood Services with Coram Houses) offered 2% fixed 30-year construction loans of up to $80,000 to 20 homeowners who rent the unit to tenants at or below 80% of Area Median Income for 30 years; all 20 slots are filled and applications are closed..
| 1-Bedroom Rent | $1,200-$1,550 (Zillow Sept 2026 average $1,195; RentCafe Aug 2026 $1,414; HUD FY2027 Fair Market Rent $1,554 for Durham-Chapel Hill)/month |
| 2-Bedroom Rent | $1,550-$1,750 (Zillow $1,560; RentCafe $1,632; HUD FY2027 FMR $1,745). Durham rents were flat to slightly down year over year in 2026/month |
| Annual Rental Income (est.) | $16,500/year |
| Payback Period (est.) | 16.7 years |
| Short-Term Rental | The UDO (amended through June 2026) has no short-term-rental use category and Sec. 5.4.2 puts no rental or occupancy condition on ADUs, so zoning does not bar nightly rental; verify current City Code and any HOA covenants before listing. |
| Overall ROI Estimate | Gross yield roughly 5-9% before expenses: $1,400-$1,550/mo ($17,000-$18,600 a year) on a $200,000-$300,000 build; net return is lower after property tax, insurance, vacancy and maintenance |
A typical ADU in Durham generates approximately $16,500 per year in rental income based on average 1-bedroom rents. At an average construction cost of $275,000, the estimated payback period is 16.7 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in Durham 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 Durham: $65,000-$140,000.
2. Prefab/modular ADUs offer predictable pricing and faster timelines. Average: $80,000-$137,000.
3. Pre-approved plans — Durham 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 Durham. 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.