| Max size | 1,000 sq ftconfirmed with the town |
|---|---|
| Min size | 400 sq ftconfirmed with the town |
| Bedrooms | Not statedoccupancy capped at one family |
| Type | Attached or detacheddetached banned in cluster develop. |
| Parking | 2 spots for ADU and 2 for existing dwellingconfirmed with the town |
| Owner-occupancy | Requiredin either the ADU or the primary home |
| Short-term rental | Short-term rental prohibitedmonth-to-month minimum if rented |
| Utility connection | Tie into the existing electrical connection or choose a separate metersame statewide |
The July 2025 state law (RSA 674:71–73) overrides local ordinance language that conflicts with it — even language a town still has posted. Here's what that means in Stratham:
State law caps what the town can add for the ADU itself at ONE extra space beyond whatever it already requires for the house — and you get to choose where that space goes. Stratham's rules still say you need 4 total parking spaces (2 for the house, 2 for the ADU); requiring a second dedicated ADU space is very likely unenforceable as written.
State law forbids the town from dictating where your entrance goes — that choice belongs to the homeowner. Stratham's rule forcing any new ADU entrance to the side or rear of the house is very likely superseded.
If Residential Open Space Cluster Developments are zoned to allow single-family homes, a flat ban on detached ADUs there looks like exactly the kind of district-wide detached-ADU prohibition HB 577 was written to eliminate. It's possible the town could argue these developments are a distinct approval type rather than a normal 'district,' which is why this needs a land-use attorney's read rather than a flat call.
Stratham exempts existing structures being converted (which matches the spirit of state law), but imposes a 50-ft front setback on any brand-new detached ADU structure specifically — a number that isn't tied to the underlying district's normal accessory-structure setback. Whether that ADU-specific setback is allowed to be stricter than the general accessory-structure rule is a legal question that needs the full statute text and Stratham's dimensional table to resolve.
State law doesn't clearly say whether a town can restrict an ADU to non-transient use. This may be a legitimate town power (similar to how towns can restrict short-term rentals generally) rather than an HB 577 conflict — treat it as an open legal question, not as superseded.
CONFIRMED WITH THE TOWN (August 19, 2026) — ADUs allowed: 1; maximum size 1,000 sq ft; minimum size 400 sq ft; impact fees: No; parking: 2 spots for ADU and 2 for existing dwelling; detached-unit distance rule: No; setbacks: Residential Agriculture - 20’ Side 20’ rear 30’ front. Town contact: Vanessa Price - Director of Planning & Building (603) 772-7391 .ext 147.
Detached ADUs cannot include a pool or garage if one already exists on the property.
Pat confirmed requirments on August 19, 2026
Stratham is one of the friendlier towns on the headline question: it permits one ADU — attached (inside the single-family home) or detached (inside an accessory structure) — by right on any legal lot already approved for or developed with a detached single-family dwelling, with a building permit and occupancy permit from the Building Department (no special exception or board hearing required except in genuinely ambiguous cases). That matches the core guarantee of the July 1, 2025 state law (RSA 674:71-73 as amended by HB 577): one by-right ADU wherever single-family homes are allowed. Owner-occupancy is required in either unit (a requirement state law permits), size must run 400-1,000 sq ft (detached ADUs additionally capped at 50% of the primary home's gross interior square footage — and the 1,000 sq ft ceiling is comfortably above the 750 sq ft minimum cap state law allows a town to impose), and detached ADUs built in a repurposed pre-3/8/2022 structure get a break on the 50-ft front setback if they don't grow the footprint more than 15% or add height. Where Stratham's PUBLISHED rules (last revised March 2022, over three years before HB 577 took effect) are likely now superseded: (1) parking — the town calls for 2 spaces for the house PLUS 2 spaces for the ADU (4 total), while state law caps what a town can require specifically for the ADU at ONE additional space, chosen by the owner on-site or off-site; (2) entrance placement — Stratham requires any new ADU entrance to go on the side or rear of the building, but state law bars municipalities from dictating ingress/egress location; (3) detached ADUs are flatly banned inside Residential Open Space Cluster Developments, which may conflict with the state mandate to permit one detached ADU in every district that allows single-family homes (an attorney call, since it's unclear whether such developments count as a 'district' for this purpose); (4) the ADU-specific 50-ft front setback on new detached structures may or may not be allowed to be stricter than the town's general accessory-structure setback — unresolved without the full ordinance text; (5) the short-term-rental ban and month-to-month minimum-tenancy rule aren't clearly addressed by state law either way and may be a legitimate town power. Because there is no indication Stratham has revised §5.4 since the 2025 law took effect, treat the parking and entrance-location rules in particular as likely unenforceable as written, and confirm current practice with the Planning Department (603-772-7391) before designing around them.
Get a free personalized report for your address in Stratham — including where the 2025 law works in your favor.
Get My Free Stratham ADU Report →House Bill 577 (2025) amended RSA 674:72, effective July 1, 2025. Wherever Stratham's ordinance is stricter than this floor, the state law controls. Read the full NH ADU law explainer →
Yes — Stratham allows one accessory dwelling unit (attached or detached) by right on any lot with a single-family home, matching the 2025 state law's core guarantee; but its published rules were last revised in March 2022, and where they conflict with state law — like double parking requirements — state law wins. Under RSA 674:72 (as amended effective July 1, 2025), one accessory dwelling unit — attached or detached — is allowed by right on single-family lots statewide.
1,000 sq ft — confirmed with the town. State law doesn't let any town cap ADU size below 750 sq ft.
Attached or detached (detached banned in cluster develop.). Since July 1, 2025, state law allows detached ADUs by right statewide — town provisions that prohibited them are superseded.
2 spots for ADU and 2 for existing dwelling — confirmed with the town. State law caps what any town can require at one additional space, located on- or off-site at the owner's choice.
Required — in either the ADU or the primary home. Where owner-occupancy is required, state law lets the owner choose which unit to live in.