Tonawanda, NY Accessory Structures: ADU Rules (2026)

The Town Board's Article 24 additional-use standards, adopted to let residents add housing while preserving low-density neighborhood character, set specific limits on accessory dwelling units (ADUs) and in-law suites in the Town of Tonawanda. Under § 215-24.3B, only one such unit is permitted per single-family property, and it may not be created on a nonconforming lot or inside a nonconforming structure. The unit's total floor area is capped at 30% of the principal dwelling's habitable floor area and cannot include more than two bedrooms, keeping the addition secondary to the main house.

All exterior entrances to the ADU or in-law suite must open onto the side or rear facade of the primary structure, or into the rear yard, so the accessory unit does not read as a second front-facing residence from the street. Before approval, the Building Department must confirm the existing driveway can hold at least one off-street parking space beyond what the single-family home already requires; if it cannot, the ADU is not permitted. Construction, modification, addition, or demolition work for the unit also cannot discernibly change the single-family residential character of the lot or structure.

Because the use is accessory, the Code Enforcement Officer may conduct an annual inspection to confirm continued compliance with § 215-24.3 and any other applicable local, regional, or state requirement. These design limits work alongside the separate owner-occupancy affidavit requirement in § 215-24.3C, so an owner adding an ADU needs to satisfy both the physical standards here and the occupancy condition before sign-off.