Who it suits
This concept gives a parent or relative a front door of their own, one bedroom and one bath, with family a door away. Whether an attached apartment is allowed depends on your municipality and property. It’s a concept for discussion, not a completed build or an approved plan.
How it lives
Everything is on one level, with a zero-step entry, wide doors and a curbless shower, so it works for someone who uses a walker now or may later. The bedroom sits away from the shared wall for quiet. A rated wall and door separate the two homes, as the building code requires.
What changes the cost
Attaching to a house is different from building alone: the new roof and foundation have to tie into the old ones, and the main house’s electrical service, heating and septic all get checked for the added load. Those checks decide the budget more than the finishes do.
What to check with your town
Check the allowed floor area, bedroom count and owner-occupancy rules. These vary by municipality; do not assume a one-bedroom plan is permitted. Start with the town-fit table on this page and confirm the requirements with your code office before design.
What moves the price
- Tying the roof and foundation into the existing house
- Whether the main house's electrical service and heating can carry the addition
- Septic capacity for an added bedroom
- Fire separation required between the units
What to check in each municipality
A first comparison with the codes we’ve read. A listed restriction identifies a conflict with this concept. Other results require local confirmation; missing research does not mean a ban or approval. Your zoning district, your lot and the municipality’s review still decide.
| Municipality | Screen | Size rule | Checked |
|---|---|---|---|
| Town of Clarkson | Below the 600 sq ft one-bedroom minimum | No more than 30% of the main home's living space (unit minimums 450 sq ft efficiency, 600 sq ft one-bedroom) | October 4, 2026 |
| Village of Fairport | Requires local confirmation of the district, size rule and approvals | 650 sq ft | October 4, 2026 |
| Town of Penfield | Family members only, so it can’t be rented. Size limit: No more than 30% of the total area of the residence. The main house’s size alone is not enough to calculate this limit | No more than 30% of the total area of the residence | October 4, 2026 |
| Village of Pittsford | Only within this code’s size limits; check them | No square-foot cap; house-size and structure-size tests apply | October 4, 2026 |
| Town of Canandaigua | Requires local confirmation of the district, size rule and approvals | No separate cap; the district's bulk and area rules for a single-family home apply | October 3, 2026 |
| Town of East Bloomfield | Family members only, so it can’t be rented. Only within this code’s size limits; check them | Detached: 500 to 850 sq ft gross floor area. In-law apartment: no size cap found | October 3, 2026 |
| Town of Perinton | No ADU-specific route found; ask the municipality for a written determination | Not applicable | September 16, 2026 |
| City of Rochester | Rule change under study; confirm the current route with the municipality | Conversion: building at least 1,500 sq ft and lot at least 6,000 sq ft, plus unit minimums | October 4, 2026 |