Build an ADU in Rochester.
New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Rochester — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.
12 districts
Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.
Verified against the official Rochester zoning ordinance · source · 2026-07-05
- Front
- 10 ft
- Side
- 10 ft
- Rear
- 20 ft
- Max coverage
- 35% lot
- Min lot
- 10,000 sf (~0.23 ac)
Footprint 30%, height 35 ft.
- Front
- 15 ft
- Side
- 10 ft
- Rear
- 25 ft
- Max coverage
- 60% lot
- Min lot
- 30,000 sf (~0.69 ac)
Most conservative (5+ family) recorded. SF tier: 10/8/20/35%/6,000.
- Front
- 25 ft
- Side
- 5 ft
- Rear
- 20 ft
- Max coverage
- 90% lot
- Min lot
- 6,000 sf (~0.14 ac)
Front is a MAX 25 (no min). 10,000 sf/unit if no water+sewer.
- Front
- 20 ft
- Side
- 10 ft
- Rear
- 20 ft
- Max coverage
- 40% lot
- Min lot
- 45,000 sf (~1.03 ac)
Conservative 45,000 (no water/sewer). Cov 35% SF / 40% two-family.
- Front
- 0 ft
- Side
- 0 ft
- Rear
- 15 ft
- Max coverage
- —
- Min lot
- 4,000 sf (~0.09 ac)
Front min none (max 10 build-to). Side per Note 1. No coverage cap. 500 sf/DU. Max 5/min 2 stories.
- Front
- 10 ft
- Side
- 10 ft
- Rear
- 25 ft
- Max coverage
- 75% lot
- Min lot
- 10,000 sf (~0.23 ac)
Coverage 75%. Side per Note 1. 5,000 sf/DU. Max 3 stories.
- Front
- 20 ft
- Side
- 10 ft
- Rear
- 25 ft
- Max coverage
- 85% lot
- Min lot
- 20,000 sf (~0.46 ac)
Coverage 85%. Side per Note 1. Max 3 stories.
- Front
- —
- Side
- —
- Rear
- —
- Max coverage
- —
- Min lot
- —
All values '—' in the table. Frontage 50 only. Controlled by Granite Ridge Development District regs, not Article 19.
- Front
- 25 ft
- Side
- 20 ft
- Rear
- 25 ft
- Max coverage
- 75% lot
- Min lot
- 40,000 sf (~0.92 ac)
GI+RI shared block, tiered by utilities; conservative (no water/sewer). Coverage 75%. Height 55 ft. Side per Note 1.
- Front
- 25 ft
- Side
- 20 ft
- Rear
- 25 ft
- Max coverage
- 75% lot
- Min lot
- 40,000 sf (~0.92 ac)
Same block as GI. Conservative tier. Coverage 75%.
- Front
- —
- Side
- 10 ft
- Rear
- 25 ft
- Max coverage
- 85% lot
- Min lot
- —
No lot min/frontage/street setback (front null). Side 10/rear 25 to any lot line. Coverage 85% (non-SF).
- Front
- —
- Side
- 50 ft
- Rear
- 50 ft
- Max coverage
- —
- Min lot
- —
Min-to-any-street 35 (recorded as null front — not a conventional street setback); min-to-any-lot-line 50 side & rear. Aviation Overlay.
Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.
Rochester ADU FAQ
Yes. Under NH RSA 674:71-73 (HB 577), one accessory dwelling unit is allowed by-right on single-family lots statewide, including Rochester (Strafford County). A detached ADU can be up to 950 sf.
In Rochester's R1 zone, ADUs follow the single-family setbacks: 10 ft front, 10 ft side, and 20 ft rear. Rochester has 12 zoning districts in total — see the full table below. Confirm your exact zone with the town.