What this is
The Family Two-Bedroom is a concept. It is an original idea we drew for households where two people each need a door that closes. It is not a finished build and it is not an approved plan. A real version starts with your lot, your town’s rules and drawings from a licensed designer.
The shared rooms sit in the middle: a living room open to the kitchen. One bedroom sits at each end of the house, so two people on different schedules don’t share a wall.
Who it suits
- A parent plus a live-in caregiver, each with a real bedroom.
- An adult child with a partner or roommate.
- A long-term tenant who needs a second room for a child or a home office, if your town allows rentals.
Two-bedroom ADUs are less common than one-bedrooms. In a 2021 survey of new California ADUs, 17% had two bedrooms and 61% had one (UC Berkeley Center for Community Innovation, 2021). That survey is from California, not New York, but here too some towns cap bedrooms, as the last section explains.
How it lives
You come in through a mudroom with the laundry beside it, which keeps winter boots and wet coats out of the living space. The kitchen opens to the living room, with a pantry wall for storage.
The bathroom and a linen closet sit off a short hall next to the first bedroom, and the second bedroom opens off the living room. A mechanical closet holds the water heater and a fresh-air unit. A tightly sealed new home has to have mechanical ventilation under New York’s residential code (2025 Residential Code of New York State, sec. R325.3), so it needs a home in the plan from the start.
What changes the cost
- Septic. New York sizes household septic systems by bedrooms, at 110 gallons a day per bedroom for new construction (10 NYCRR Appendix 75-A.3). A three-bedroom house plus this cottage adds up to five bedrooms. The state’s minimum tank for five bedrooms is 1,500 gallons, compared with 1,000 gallons for one to three (10 NYCRR Appendix 75-A.6). The office that reviews septic systems decides whether the two homes are counted together or need separate systems. In Ontario, Wayne and Yates counties that is the NYS Department of Health’s Geneva District Office, not the county.
- Foundation. Footings must be protected from frost, by going below the frost line or with an insulated shallow design, among other methods (2025 Residential Code of New York State, sec. R403.1.4.1).
- Electrical service. Heat, hot water, cooking and drying all run on electricity in a heat-pump home. An electrician should check whether your panel can carry it or the cottage needs its own service.
What to check with your town
Two bedrooms is where many local rules push back:
- Bedroom caps. The Town of Clarkson allows one bedroom (Town of Clarkson, sec. 140-23.4). The Village of Pittsford allows up to two (Village of Pittsford, sec. 210-24.3).
- Size caps. The Village of Fairport caps an ADU at one bedroom and 650 square feet (Village of Fairport, sec. 551-26). The Village of Phelps caps it at 720 square feet (Village of Phelps, sec. 175-10.19). Ask exactly how your town measures size, because a footprint and an interior area are different numbers.
- Owner occupancy. Many towns require the owner to live in the house or the ADU, and Pittsford can revoke the permit if the owner stops living there (Village of Pittsford, sec. 210-24.3).
- Parking. Pittsford also requires room for one more off-street parking space in the existing driveway (Village of Pittsford, sec. 210-24.3).
Look up your area on the New York rules page, or start with the property checker.
What moves the price
- Septic capacity for the added bedrooms
- Foundation type and local frost depth
- Distance to water, sewer or septic, and power
- Electrical service size for an all-electric home
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 | Over the 1-bedroom limit | 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 | Detached restriction: Detached ADUs are prohibited | 650 sq ft | October 4, 2026 |
| Town of Penfield | Detached units are excluded from the researched in-law route | 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, and a detached unit must be removed when family stops using it. 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 | Detached restriction: Living in accessory buildings is barred in the covered residential districts | 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 |