Nashua, New Hampshire · Hillsborough County

Build an ADU in Nashua.

Allowed by-right · RSA 674:71-73

New Hampshire's HB 577 lets you add one accessory dwelling unit on your single-family lot in Nashua — by-right. A detached ADU can be up to 950 sf, and ADU setbacks match your lot's single-family setbacks.

All zoning districts in Nashua

15 districts

Each district's single-family setbacks — which your ADU follows. The primary residential district is highlighted.

Verified against the official Nashua zoning ordinance · source · 2026-07-05

R-9Primary

Residential (R-9)

Table 16-3

Front: 20 ft
Side: 10 ft
Rear: 30 ft
Max coverage: —
Min lot: 9,000 sf (~0.21 ac)

Open Space 50%; height 35 ft/2.5. Width 90, frontage 75. No coverage column.

R-40

Residential (R-40)

Table 16-3

Front: 40 ft
Side: 25 ft
Rear: 50 ft
Max coverage: —
Min lot: 40,000 sf (~0.92 ac)

Open Space 75%. Width 150, frontage 120.

R-30

Residential (R-30)

Table 16-3

Front: 30 ft
Side: 20 ft
Rear: 40 ft
Max coverage: —
Min lot: 30,000 sf (~0.69 ac)

Open Space 60%.

R-18

Residential (R-18)

Table 16-3

Front: 20 ft
Side: 20 ft
Rear: 40 ft
Max coverage: —
Min lot: 18,000 sf (~0.41 ac)

Open Space 50%.

R-A

Residential-A (R-A)

Table 16-3

Front: 25 ft
Side: 10 ft
Rear: 25 ft
Max coverage: —
Min lot: 7,500 sf (~0.17 ac)

Open Space 50%; FAR 0.5.

R-B

Residential-B (R-B)

Table 16-3

Front: 10 ft
Side: 7 ft
Rear: 20 ft
Max coverage: —
Min lot: 6,000 sf (~0.14 ac)

Open Space 35%; FAR 0.5. Height 45 ft/3.

R-C

Residential-C (R-C)

Table 16-3

Front: 10 ft
Side: 7 ft
Rear: 20 ft
Max coverage: —
Min lot: 5,000 sf (~0.11 ac)

Side min 7/max 20. Open Space 35%; FAR 1.0. Height 100 ft/10.

Local Business (LB)

Table 16-3

Front: 10 ft
Side: 7 ft
Rear: 20 ft
Max coverage: —
Min lot: —

Front min 10/max 20. Open Space 10%; FAR 0.75.

General Business (GB)

Table 16-3

Front: 10 ft
Side: 7 ft
Rear: 10 ft
Max coverage: —
Min lot: 10,000 sf (~0.23 ac)

Open Space 10%; FAR 1.25. Height 60 ft/5.

D-1

Downtown 1 (D-1)

Table 16-3

Front: 0 ft
Side: 0 ft
Rear: 10 ft
Max coverage: —
Min lot: —

Front/side min 0, max 10 (build-to). Height 90 ft/6.

D-3

Downtown 3 (D-3)

Table 16-3

Front: 0 ft
Side: 0 ft
Rear: 10 ft
Max coverage: —
Min lot: —

Front/side min 0, max 10. Height 60 ft/4. (No D-2 exists.)

Highway Business (HB)

Table 16-3

Front: 20 ft
Side: 10 ft
Rear: 20 ft
Max coverage: —
Min lot: 20,000 sf (~0.46 ac)

Open Space 20%; FAR 0.75.

Park Industrial (PI)

Table 16-3

Front: 30 ft
Side: 20 ft
Rear: 20 ft
Max coverage: —
Min lot: 30,000 sf (~0.69 ac)

Open Space 20%. Height 75 ft/5.

General Industrial (GI)

Table 16-3

Front: 10 ft
Side: 10 ft
Rear: 15 ft
Max coverage: —
Min lot: 5,000 sf (~0.11 ac)

Open Space 10%; FAR 2.0.

Airport Industrial (AI)

Table 16-3

Front: 30 ft
Side: 30 ft
Rear: 50 ft
Max coverage: —
Min lot: 40,000 sf (~0.92 ac)

Open Space 20%. Height 45 ft/2.

Form-based and downtown districts may use build-to lines instead of fixed setbacks (shown as “—”); verify your parcel's district before you build.

Confirm your zoning

Nashua zoning ordinance ↗Nashua parcel map (MapGeo) ↗

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Nashua ADU FAQ

Can I build an ADU in Nashua, NH?

Yes. Under NH RSA 674:71-73 (HB 577), one accessory dwelling unit is allowed by-right on single-family lots statewide, including Nashua (Hillsborough County). A detached ADU can be up to 950 sf.

What are the ADU setbacks in Nashua?

In Nashua's R-9 zone, ADUs follow the single-family setbacks: 20 ft front, 10 ft side, and 30 ft rear. Nashua has 15 zoning districts in total — see the full table below. Confirm your exact zone with the town.

ADU rules in nearby Hillsborough County towns

Amherst Antrim Bedford Bennington Brookline Deering Francestown Goffstown