Grannio

Can You Build an ADU in Dover?

Yes — Dover is governed by New Hampshire's statewide ADU law, which limits what the city can restrict. A 700 sq ft detached ADU here runs about $161,500–$264,500.

Construction costs in Dover track close to the New Hampshire state average.

Detached ADU (700 sq ft)

$161,500–$264,500

Garage conversion (400 sq ft)

$50,500–$92,500

Statewide protection

Yes

What applies in Dover

New Hampshire requires municipalities to allow one attached ADU by right in any zone that permits single-family homes. Detached ADUs and additional standards are set locally.

Because New Hampshire has a statewide ADU law (RSA 674:71–73), Dover must follow these minimums even where its older zoning code is stricter. Confirm fees and design standards with the Dover planning department.

Estimate your Dover ADU cost

Your property

ADU type

Estimated cost in New Hampshire

$161,500 – $264,500

≈ $231–$378/sq ft turnkey · midpoint $213,000

$144,900
Construction
$38,300
Design & permits
$29,800
Site work
Good news — building an ADU in New Hampshire is very likely allowed.
  • iSize set locally. This state leaves ADU size limits to your city — typical caps run 600–1,200 sq ft. Check your local code.
  • ✓No extra parking likely required. Set by local ordinance — commonly 1 space per ADU unless near transit.
  • iOwner-occupancy varies. Owner-occupancy rules are set locally in this state.
  • ✓Lot has room. A 700 sq ft ADU uses about 12% of your 6,000 sq ft lot — comfortably within typical coverage limits.

Rule basis: RSA 674:71–73

If you rent it out

$1,125–$1,825

est. rent/mo

8.3%

gross yield

12.9 yrs

payback

~$16,461/yr after a 7% vacancy allowance, before financing & maintenance.

Financed over 20 yrs at 7.5%, the build is about $1,716/mo — vs ~$1,475/mo in estimated rent.

Get your detailed feasibility report →

Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.

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Other New Hampshire cities

ManchesterNashuaConcordPortsmouth

Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.