Carmel ADU Zoning Guide

Last reviewed 2026-04-26

Owner occupancyRequired

Carmel's zoning code supports ADU development on qualifying single-family properties, providing flexible housing options for creative homeowners. Whether you're considering multigenerational housing for family members, a rental unit with reliable income, or an independent living space for caregivers or assistants, understanding the local zoning rules is essential to moving forward with confidence. We've reviewed Carmel's zoning regulations in detail and outlined the key requirements below. Rules can change, so confirm details with the Carmel Planning Department or book a free consultation with our team before starting your project.

Status

Adoption status: Active — ADUs are governed by §156-15 of the Town of Carmel Zoning Code; the entire Chapter 156 was comprehensively updated in March/June 2025 following a public hearing on June 18, 2025
Governing ordinance: Town of Carmel Zoning Code, Chapter 156, §156-15 (March 2025 version)
Prior version: Prior ADU regulation was at §156-45.2 (now replaced by §156-15 in the 2025 code reorganization)

Eligibility

Where ADUs are allowed

Zoning districts permitted: LDR (Low Density Residential, 3-acre minimum lot) and MDR (Medium Density Residential, 1-acre minimum lot) only
Lot type / use restrictions: Single-family detached dwellings only; ADU may be within the principal dwelling or within a pre-existing accessory building; no new detached structures created for ADU purposes
Minimum lot area required: LDR zone: 3 acres; MDR zone: 1 acre
Limit per property: One ADU per property
Appearance restriction: Principal building must retain single-family appearance with only one front entrance; any additional entrances must be on the side of the building

Types allowed

Attached ADU (interior conversion): Yes — within the existing footprint of the principal dwelling; no expansion of the building footprint is permitted
Detached ADU (existing pre-existing accessory building conversion): Yes — in a pre-existing accessory building (garage, carriage house, etc.) that existed as of the code effective date
Detached ADU (new construction): No — new accessory structures for ADU purposes are not permitted; only conversion of pre-existing accessory buildings
Attached ADU (addition expanding footprint): No — building footprint may not be expanded to create an ADU

Size and placement

Size limits

Minimum sq ft: 400 sq ft of habitable floor area
Maximum (attached — within principal dwelling): 35% of the habitable floor area of the principal single-family detached dwelling
Maximum (detached — in pre-existing accessory building): 650 sq ft of habitable floor area
Maximum bedrooms: 2 bedrooms
Detached maximum distance from principal dwelling: Detached ADU in an accessory building may not be located more than 500 ft from the closest exterior wall of the principal dwelling

Setbacks

General rule: ADU must comply with all bulk regulations (yard setbacks, lot coverage, height) applicable to a single-family dwelling in the LDR or MDR district per the Schedule of District Regulations (§156-9)
Specific numeric setbacks by zone (from Schedule §156-9): Not reproduced in the retrieved sections; consult the Schedule of District Regulations at the end of the 2025 Zoning Code or contact the Building Department

Rules for use

Parking

Requirement: 1 off-street parking space per bedroom in the ADU, in addition to all parking required for the principal single-family dwelling
Standards: Parking must comply with dimensional, setback, and access requirements in §156-43 (Off-Street Parking)

Owner occupancy

Required: Yes — the property owner must reside in either the principal dwelling or the ADU
Transfer: If ownership of the property is transferred, the new owner must comply with owner occupancy requirements within 60 days or the ADU permit may be revoked
Vacation of owner: If the owner vacates the property, they must remove the ADU within 30 days

Rental use

Short-term rental: Explicitly prohibited — the ADU may not be used as a short-term rental
Long-term rental: Permitted

How to apply in Carmel

Approval authority: Building Inspector (not ZBA or Planning Board for standard ADU applications)
Application requirements: Application must include: owner information, lot details, floor area calculations, proposed parking, Putnam County Department of Health approval of water supply and sewage disposal, survey, floor plans, notarized authorization for inspection, and fee
Putnam County Health Dept. approval: Required — evidence of approval from the Putnam County Department of Health for water supply and sewage disposal must be provided; if on Town water/sewer, Town Engineer approval is also required
Building permit + CO: Required; must comply with NYS Building Code
Permit validity: ADU permit is valid for 3 years, renewable annually with owner occupancy certification and payment of renewal fee
Decision timeline: Building Inspector must approve or deny within 30 days of complete application
Contact: Town of Carmel Building Department, 60 McAlpin Avenue, Mahopac, NY 10541

State-level context

Putnam County Health Dept. renewal (county-level). The Putnam County Department of Health issues its own separate 3-year approval (renewable) for water supply and sewage disposal adequacy; fee is $100; requires coliform bacteria water sample, septic pumping receipt, site plan showing well/septic/parking, Certificate of Occupancy

Putnam County Health — ownership change voids permit. A change of ownership voids the Putnam County Health permit; the new owner cannot renew the old permit — they must reapply

Plus One ADU Program. Putnam County is not listed as a current participating county in the HCR Plus One ADU Program based on retrieved sources; the Westchester Habitat program (Croton-on-Hudson, Dobbs Ferry, Hastings-on-Hudson, Irvington, Cortlandt, Yorktown) does not include Carmel

NY state preemption. No statewide ADU preemption law enacted in New York as of April 2026

Recent and pending changes

June 2025 comprehensive code update
The Town Board approved amendments to Chapter 156 in June 2025 following a public hearing on June 18, 2025. The update reorganized the zoning code (ADU moved from §156-45.2 to §156-15), reduced residential zoning from three to one acre (MDR minimum lot), and added new uses including mixed-use and ADU provisions
January 2026 ZBA case — 650 sq ft cap confirmed
A ZBA applicant at 737 Croton Falls Rd (LDR zone) sought a size variance above the 650 sq ft cap for an accessory apartment; confirms the 650 sq ft detached limit is actively enforced

Important details

Putnam County Health approval is mandatory and separate: Do not begin construction without first obtaining Putnam County Department of Health approval of your water supply and sewage disposal. The county issues its own 3-year permit that must be renewed independently of the Town building permit. Change of ownership automatically voids the county permit
No new detached structures: You cannot build a brand-new carriage house or backyard cottage as an ADU in Carmel; you can only convert a pre-existing accessory building (garage, etc.) or add an interior conversion within the principal dwelling
3-year permit, renewed annually after 1st year: The ADU permit is valid for 3 years; after the initial 3-year period it must be renewed annually with an owner occupancy certification — failure to renew is grounds for revocation
Removal on owner departure: If the owner vacates the property (no longer occupying principal dwelling or ADU), the ADU must be removed within 30 days

Frequently asked questions

Are ADUs allowed by right in Carmel?

No, ADUs in Carmel are not broadly permitted by right across all single-family zones. Many ADU proposals require approval from the Board of Zoning Appeals as a variance or special use permit.

What were Carmel's proposed ADU limits in the draft ordinance?

Carmel's 2020 draft ordinance proposed limits such as one ADU per lot, specific square footage ranges, bedroom caps, and height relationships to the main house, but this ordinance was not adopted.

Should I contact Carmel's Planning Board before proposing an ADU?

Yes, contact the Town of Carmel Building Department at 845-628-1500 or the Planning Board to understand current ADU requirements and approval processes for your property's zoning district.

Sources (5)

Last reviewed 2026-04-26. Local rules can change — verify the latest details with the Carmel planning department, or book a free consultation with our team before starting your project. This page is informational and is not legal advice.

Carmel ADU regulations.