Beacon · ADU cost
What it costs to build an ADU in Beacon, NY
An 800 sq ft accessory dwelling unit in Beacon runs roughly $210k–275k, or about $263–345/sq ft, and that per-square-foot figure sits deliberately above the $215–282/sq ft a full house costs here. An ADU still needs one whole kitchen, one whole bath, its own service panel and its own heating plant no matter how small you draw it, and those costs do not shrink with the floor plan, so they land on half the square footage and push the rate up. Whether the city will let you build one is a separate question from what it costs, and it gets answered parcel by parcel rather than townwide, since the City of Beacon maps 23 districts that treat accessory units differently from one another, so read the table below as a starting point rather than a verdict.
ADU cost by size in Beacon
Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Dutchess County pricing, before the service and septic work a second dwelling can trigger.
| Size | Type | $ / sq ft | Estimated total |
|---|---|---|---|
| 400 sq ft | Studio | $349–$457 | $140k–185k |
| 600 sq ft | One bedroom | $292–$382 | $175k–230k |
| 800 sq ft | One bedroom, larger | $263–$345 | $210k–275k |
| 1,000 sq ft | Two bedroom | $246–$322 | $245k–320k |
400 sq ft — One room plus a bath. Garage conversions and small backyard cottages land here.
600 sq ft — The most common detached build - a real bedroom, full kitchen, one bath.
800 sq ft — Room for a proper living area. Still a single bath and one kitchen.
1,000 sq ft — About as large as most codes allow an accessory unit to go.
Why the rate is higher than a house
The systems below are priced for an 800 sq ft unit. The middle column is what each system would cost if it simply shrank with the floor plan; the left column is what it actually costs once you account for the equipment a dwelling needs one of regardless of size. The gap between the two columns is the whole reason small builds price the way they do.
| System | $ / sq ft in an ADU | If it scaled with floor area | Fixed per unit |
|---|---|---|---|
| Site work | $8–$12 | $8 | — |
| Foundation | $17–$24 | $17 | — |
| Framing | $27–$34 | $27 | — |
| Envelope - roof, siding, windows | $34–$43 | $34 | — |
| Plumbing | $29–$36 | $17 | 55% |
| Electrical | $19–$25 | $13 | 35% |
| HVAC | $24–$30 | $15 | 45% |
| Insulation | $8–$10 | $8 | — |
| Interior finishes | $34–$46 | $29 | 15% |
| Millwork & cabinetry | $19–$29 | $12 | 55% |
The fixed-per-unit share is a modeling assumption, not a figure from the code: it is our estimate of how much of each system's budget buys equipment a dwelling needs exactly one of - a kitchen rough-in, a bath group, a service panel, a heating plant - and therefore does not shrink when the unit does. Site work, foundation, framing, envelope and insulation are treated as scaling straight with floor area, which understates the premium slightly, because a small building carries more envelope per square foot of floor than a large one.
What the Beacon code says about accessory units
Whether you can build one, and how large, is decided by the district your parcel sits in rather than by the town as a whole. The table shows how each mapped district treats ADUs alongside the lot and setback standards a second unit still has to fit inside. District boundaries and conditions vary, so treat it as a starting point and confirm the district that applies to your parcel.
| District | Min lot | Setbacks F / S / R | Max height | ADU |
|---|---|---|---|---|
| One-Family Residence 120,000 Square Feet | 2.7548 ac | 70 / 50 / 75 ft | 35 ft | Occupancy restricted |
| One-Family Residence 80,000 Square Feet | 1.8365 ac | 45 / 30 / 50 ft | 35 ft | Occupancy restricted |
| One-Family Residence 40,000 Square Feet | 0.9183 ac | 35 / 25 / 50 ft | 35 ft | Occupancy restricted |
| One-Family Residence 20,000 Square Feet | 0.4591 ac | 25 / 20 / 40 ft | 35 ft | Occupancy restricted |
| One-Family Residence 10,000 Square Feet | 0.2296 ac | 20 / 15 / 35 ft | 35 ft | Occupancy restricted |
| One-Family Residence 7,500 Square Feet | 0.1722 ac | 15 / 10 / 25 ft | 35 ft | Occupancy restricted |
| One-Family Residence 5,000 Square Feet | 0.1148 ac | 10 / 10 / 20 ft | 35 ft | Occupancy restricted |
| Residence District 7,500 Square Feet per Unit | 2 ac | 20 / 25 / 50 ft | 35 ft | — |
| Residence District 6,000 Square Feet per Unit | 2 ac | 50 / 25 / 50 ft | 35 ft | — |
| Residence District 5,000 Square Feet per Unit | 0.1148 ac | 30 / 10 / 25 ft | 35 ft | — |
| Residence District 4,000 Square Feet per Unit | 0.1148 ac | 40 / 20 / 40 ft | 35 ft | — |
| Residence District 3,000 Square Feet per Unit | 0.1148 ac | 30 / 20 / 25 ft | 45 ft | — |
| Residence District 1,800 Square Feet per Unit | 0.1148 ac | 30 / 20 / 25 ft | 100 ft | — |
| Residence District 1,700 Square Feet per Unit | 0.1148 ac | 30 / 20 / 25 ft | 55 ft | — |
| Transitional | 0.1148 ac | 10 / 10 / 20 ft | 35 ft | Occupancy restricted |
| General Business | — | 15 / 20 / 25 ft | 35 ft | Occupancy restricted |
| Corridor Mixed-Use Service | — | 0 / 0 / 20 ft | 38 ft | Occupancy restricted |
| Linkage | — | 0 / 0 / 25 ft | 48 ft | — |
| Fishkill Creek Development | 2 ac | — | 40 ft | — |
| Waterfront Park | 1 ac | 10 / - / - ft | 35 ft | — |
| Tidal Shoreline | 3 ac | — | — | — |
| Light Industrial | — | 20 / 20 / 25 ft | 35 ft | Occupancy restricted |
| Heavy Industrial | — | 30 / 20 / 25 ft | 40 ft | — |
One-Family Residence 120,000 Square Feet — Lot area is set twice — an overall minimum and 120,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 250 ft and minimum lot DEPTH 350 ft; depth is a separate test from area and width. No building may contain more than 1 dwelling unit. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
One-Family Residence 80,000 Square Feet — Lot area is set twice — an overall minimum and 80,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 150 ft and minimum lot DEPTH 200 ft; depth is a separate test from area and width. No building may contain more than 1 dwelling unit. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
One-Family Residence 40,000 Square Feet — Lot area is set twice — an overall minimum and 40,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 150 ft and minimum lot DEPTH 150 ft; depth is a separate test from area and width. No building may contain more than 1 dwelling unit. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
One-Family Residence 20,000 Square Feet — Lot area is set twice — an overall minimum and 20,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 125 ft and minimum lot DEPTH 125 ft; depth is a separate test from area and width. No building may contain more than 1 dwelling unit. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
One-Family Residence 10,000 Square Feet — Lot area is set twice — an overall minimum and 10,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 85 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. No building may contain more than 1 dwelling unit. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
One-Family Residence 7,500 Square Feet — Lot area is set twice — an overall minimum and 7,500 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 75 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. No building may contain more than 1 dwelling unit. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
One-Family Residence 5,000 Square Feet — The lot is 5,000 sq ft but the area PER UNIT is 2,500, so two dwelling units are allowed on it — the only R1 district where the two figures differ. Lot area is set twice — an overall minimum and 2,500 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 50 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. No building may contain more than 2 dwelling units. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Residence District 7,500 Square Feet per Unit — In any RD or T District the Planning Board may approve subdivision into individual lots of as little as 1,800 sq ft each for attached or semi-attached single-family dwellings, provided the gross density over the whole tract stays within what the district allows for multiple dwellings; it may also cut the side yards to ZERO for such a subdivision, except that an end unit keeps at least half the side yard of the least restrictive adjoining residential district. A multifamily development also needs a landscaped recreation or usable open space area of 2,000 sq ft for the first 20 dwelling units and 100 sq ft for each unit beyond that. The front yard is published as a RANGE, 20 to 35 ft, not a plain minimum. Lot area is set twice — an overall minimum and 7,500 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 200 ft and minimum lot DEPTH 200 ft; depth is a separate test from area and width. Building coverage is published twice: 15% for a MULTIFAMILY building and 20% for anything else. The figure recorded is the all-other one. No building may contain more than 12 dwelling units. Buildings on the same lot must stand at least 30 ft apart. Height is capped at 3 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Residence District 6,000 Square Feet per Unit — In any RD or T District the Planning Board may approve subdivision into individual lots of as little as 1,800 sq ft each for attached or semi-attached single-family dwellings, provided the gross density over the whole tract stays within what the district allows for multiple dwellings; it may also cut the side yards to ZERO for such a subdivision, except that an end unit keeps at least half the side yard of the least restrictive adjoining residential district. A multifamily development also needs a landscaped recreation or usable open space area of 2,000 sq ft for the first 20 dwelling units and 100 sq ft for each unit beyond that. Lot area is set twice — an overall minimum and 6,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 200 ft and minimum lot DEPTH 200 ft; depth is a separate test from area and width. Building coverage is published twice: 15% for a MULTIFAMILY building and 20% for anything else. The figure recorded is the all-other one. No building may contain more than 16 dwelling units. Buildings on the same lot must stand at least 30 ft apart. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Residence District 5,000 Square Feet per Unit — In any RD or T District the Planning Board may approve subdivision into individual lots of as little as 1,800 sq ft each for attached or semi-attached single-family dwellings, provided the gross density over the whole tract stays within what the district allows for multiple dwellings; it may also cut the side yards to ZERO for such a subdivision, except that an end unit keeps at least half the side yard of the least restrictive adjoining residential district. A multifamily development also needs a landscaped recreation or usable open space area of 2,000 sq ft for the first 20 dwelling units and 100 sq ft for each unit beyond that. Lot area is set twice — an overall minimum and 5,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 50 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. Building coverage is published twice: 20% for a MULTIFAMILY building and 30% for anything else. The figure recorded is the all-other one. No building may contain more than 16 dwelling units. Buildings on the same lot must stand at least 30 ft apart. Height is capped at 3 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Residence District 4,000 Square Feet per Unit — In any RD or T District the Planning Board may approve subdivision into individual lots of as little as 1,800 sq ft each for attached or semi-attached single-family dwellings, provided the gross density over the whole tract stays within what the district allows for multiple dwellings; it may also cut the side yards to ZERO for such a subdivision, except that an end unit keeps at least half the side yard of the least restrictive adjoining residential district. A multifamily development also needs a landscaped recreation or usable open space area of 2,000 sq ft for the first 20 dwelling units and 100 sq ft for each unit beyond that. Lot area is set twice — an overall minimum and 4,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 200 ft and minimum lot DEPTH 200 ft; depth is a separate test from area and width. Building coverage is published twice: 20% for a MULTIFAMILY building and 25% for anything else. The figure recorded is the all-other one. No building may contain more than 20 dwelling units. Buildings on the same lot must stand at least 30 ft apart. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Residence District 3,000 Square Feet per Unit — In any RD or T District the Planning Board may approve subdivision into individual lots of as little as 1,800 sq ft each for attached or semi-attached single-family dwellings, provided the gross density over the whole tract stays within what the district allows for multiple dwellings; it may also cut the side yards to ZERO for such a subdivision, except that an end unit keeps at least half the side yard of the least restrictive adjoining residential district. A multifamily development also needs a landscaped recreation or usable open space area of 2,000 sq ft for the first 20 dwelling units and 100 sq ft for each unit beyond that. Lot area is set twice — an overall minimum and 3,000 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 50 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. Building coverage is published twice: 20% for a MULTIFAMILY building and 40% for anything else. The figure recorded is the all-other one. No building may contain more than 24 dwelling units. Buildings on the same lot must stand at least 30 ft apart. Height is capped at 3 1/2 stories as well as 45 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Residence District 1,800 Square Feet per Unit — RD-1.8 is the tallest district in the City at 10 storeys and 100 ft, but no more than 65% of the dwelling units in a development may sit in buildings over 3 1/2 storeys, and no building of 3 1/2 storeys or less may hold more than 24 units. In any RD or T District the Planning Board may approve subdivision into individual lots of as little as 1,800 sq ft each for attached or semi-attached single-family dwellings, provided the gross density over the whole tract stays within what the district allows for multiple dwellings; it may also cut the side yards to ZERO for such a subdivision, except that an end unit keeps at least half the side yard of the least restrictive adjoining residential district. A multifamily development also needs a landscaped recreation or usable open space area of 2,000 sq ft for the first 20 dwelling units and 100 sq ft for each unit beyond that. Lot area is set twice — an overall minimum and 1,800 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 50 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. Building coverage is published twice: 25% for a MULTIFAMILY building and 40% for anything else. The figure recorded is the all-other one. Buildings on the same lot must stand at least 30 ft apart. Height is capped at 10 stories as well as 100 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Residence District 1,700 Square Feet per Unit — One storey of parking underneath a building does not count toward either the storey or the height limit. No building may exceed 150 ft in length. In any RD or T District the Planning Board may approve subdivision into individual lots of as little as 1,800 sq ft each for attached or semi-attached single-family dwellings, provided the gross density over the whole tract stays within what the district allows for multiple dwellings; it may also cut the side yards to ZERO for such a subdivision, except that an end unit keeps at least half the side yard of the least restrictive adjoining residential district. A multifamily development also needs a landscaped recreation or usable open space area of 2,000 sq ft for the first 20 dwelling units and 100 sq ft for each unit beyond that. Lot area is set twice — an overall minimum and 1,700 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 50 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. Building coverage is published twice: 25% for a MULTIFAMILY building and 40% for anything else. The figure recorded is the all-other one. No building may contain more than 36 dwelling units. Buildings on the same lot must stand at least 30 ft apart. Height is capped at 4 1/2 stories as well as 55 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Transitional — The lot area per dwelling unit in T is not a figure: it is HALF the minimum lot size per dwelling unit of the least restrictive adjoining residential district, so it depends on what the parcel adjoins. In any RD or T District the Planning Board may approve subdivision into individual lots of as little as 1,800 sq ft each for attached or semi-attached single-family dwellings, provided the gross density over the whole tract stays within what the district allows for multiple dwellings; it may also cut the side yards to ZERO for such a subdivision, except that an end unit keeps at least half the side yard of the least restrictive adjoining residential district. A multifamily development also needs a landscaped recreation or usable open space area of 2,000 sq ft for the first 20 dwelling units and 100 sq ft for each unit beyond that. Minimum lot width 50 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
General Business — General Business sets no lot area, no lot width and no coverage limit, but it does set 1,500 sq ft of lot area per dwelling unit and a 100 ft minimum lot depth. Lot area is set twice — an overall minimum and 1,500 sq ft PER DWELLING UNIT — and both bind. Minimum lot width is not set and minimum lot DEPTH 100 ft; depth is a separate test from area and width. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Corridor Mixed-Use Service — The front yard is published as a RANGE, 0 to 10 ft, not a plain minimum. Minimum lot width is not set and minimum lot DEPTH 75 ft; depth is a separate test from area and width. Height is capped at 3 stories as well as 38 ft. A minimum of 10% of the lot must be open space. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Linkage — Both the front and the side yard are published as ranges rather than minimums. The front yard is published as a RANGE, 0 to 20 ft, not a plain minimum. The side yard is published as a RANGE, 0 to 30 ft. Minimum lot width is not set and minimum lot DEPTH 75 ft; depth is a separate test from area and width. Height is capped at 4 stories as well as 48 ft. A minimum of 15% of the lot must be open space. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Fishkill Creek Development — Lot area is set twice — an overall minimum and 3,960 sq ft PER DWELLING UNIT — and both bind. Height is capped at 3 stories as well as 40 ft. A minimum of 30% of the lot must be open space. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Waterfront Park — Height is capped at 2 1/2 stories as well as 35 ft. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Tidal Shoreline — The Tidal Shoreline District publishes a three-acre lot minimum and a 15% open space requirement and nothing else; its height and yards come from Article IVA. A minimum of 15% of the lot must be open space. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Light Industrial — Lot area is set twice — an overall minimum and 1,500 sq ft PER DWELLING UNIT — and both bind. Minimum lot width 60 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. A minimum of 20% of the lot must be open space. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Heavy Industrial — Minimum lot width 60 ft and minimum lot DEPTH 100 ft; depth is a separate test from area and width. A minimum of 20% of the lot must be open space. On any development proposal covering more than three acres in an R1, RD or Fishkill Creek Development district, the lot area PER DWELLING UNIT is calculated on net acreage: surface water, federal regulatory floodway, state or federally regulated wetland, and predevelopment slopes of 25% or steeper all come off the lot area first (§ 223-63).
Size limits on record in Beacon
Where the code states a size cap, it decides which row of the cost table above actually applies to you. These are the caps recorded for Beacon:
- One-Family Residence 120,000 Square FeetOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- One-Family Residence 80,000 Square FeetOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- One-Family Residence 40,000 Square FeetOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- One-Family Residence 20,000 Square FeetOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- One-Family Residence 10,000 Square FeetOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- One-Family Residence 7,500 Square FeetOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- One-Family Residence 5,000 Square FeetOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Residence District 7,500 Square Feet per UnitOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Residence District 6,000 Square Feet per UnitOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Residence District 5,000 Square Feet per UnitOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Residence District 4,000 Square Feet per UnitOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Residence District 3,000 Square Feet per UnitOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Residence District 1,800 Square Feet per UnitOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Residence District 1,700 Square Feet per UnitOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- TransitionalOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- General BusinessOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Corridor Mixed-Use ServiceOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- LinkageOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Fishkill Creek DevelopmentOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Waterfront ParkOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Tidal ShorelineOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Light IndustrialOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
- Heavy IndustrialOne accessory apartment per single-family lot; the flat 1,000 sq ft ceiling was removed
Costs an ADU adds that a house does not
- Septic and water A second dwelling adds bedrooms to the design flow, which on an unsewered parcel often means expanding or replacing the existing system rather than tapping it. This is the single most common reason an ADU budget moves after design, and it is site-specific enough that no model should quote it - get it evaluated early.
- Utility service Central Hudson territory. A detached unit needs power run to it, and whether it goes on its own meter or subfeeds the main house changes both the cost and the permit path.
- Access and parking Many codes require an added parking space for the accessory unit, and a detached unit usually needs a driveway extension or a path, both of which count against a lot-coverage or impervious-surface cap.
- Short-term rentalsShort-term rentals allowed with local rules. STR permit required for all rentals under 30 days. Primary residence only qualifies. Maximum 100 days per year; no more than 30 consecutive days per booking. Permit valid 2 years. Contact Building Dept at (845) 838-5011 for current requirements. Separate question from whether you can build the unit.
- Zoning codeecode360.com/7066171
- Building dept(845) 838-5011
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Building a full house instead?
A standard-finish house in Beacon runs $215–282/sq ft, about $390k–510k at 1,800 sq ft , plus roughly $26,630 for a conforming lot. See what it costs to build a house in Beacon.
ADU cost in nearby towns
All Dutchess County towns: Poughkeepsie (City) · Amenia · Beekman · Clinton · Dover · East Fishkill · Fishkill · Hyde Park · La Grange · Milan · North East · Pawling · Pine Plains · Pleasant Valley · Poughkeepsie · Red Hook · Rhinebeck · Stanford · Union Vale · Wappinger · Washington · Fishkill (Village) · Millbrook (Village) · Millerton (Village) · Pawling (Village) · Red Hook (Village) · Rhinebeck (Village) · Tivoli (Village) · Wappingers Falls (Village)
More on Beacon: Can you build an ADU here? · Zoning for new construction · Dutchess County build cost
ADU cost in Beacon: common questions
How much does it cost to build an ADU in Beacon, NY?
An 800 sq ft accessory dwelling unit in City of Beacon runs roughly $210k–275k at a standard finish, general-contractor margin included. A 400 sq ft studio runs about $140k–185k. Those are structure costs on an easy site and do not include the septic, water or electrical service work a second unit often triggers.
Why does an ADU cost more per square foot than a house in Beacon?
Because a lot of a dwelling's cost is per dwelling, not per square foot. One kitchen, one bath group, one service panel and one heating plant cost about the same in an 800 sq ft cottage as in a 1,800 sq ft house, so on the smaller unit they get spread over less than half the floor area. That is why an ADU here prices at $263–345/sq ft against $215–282/sq ft for a full house, even though it is the same trades doing the same work.
Are ADUs allowed in Beacon?
City of Beacon has 23 districts. 11 of 23 districts allow ADUs with occupancy restrictions. 12 districts have incomplete data - verify with the building department at (845) 838-5011. Check the specific address with the free ADU checker before you spend money on design.
Can I rent an ADU in Beacon short term?
Short-term rentals allowed with local rules for City of Beacon. ADU rules and short-term-rental rules are set separately, so a unit you are allowed to build is not automatically one you are allowed to rent nightly. Confirm both before you underwrite the build on short-term-rental income.
ADU costs are modeled estimates in current 2026 dollars at the Dutchess County regional index, general-contractor margin included, derived from Offsite's cost engine with a stated adjustment for the equipment a dwelling needs one of regardless of size. They are planning numbers for decision-support only - not a bid, quote, or guarantee, and not legal, architectural or engineering advice. They cover the structure and exclude septic expansion, utility service runs, site work beyond a flat and clear pad, and permit fees. ADU eligibility, size, owner-occupancy and permit conditions in the City of Beacon vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-08-16; verify with the building department at (845) 838-5011 before relying on any answer. Sources: Offsite / Aldo cost engine (costEngine.js + constants.js); zoning dataset (municipalData.js).