5 county-level rules, plus city-specific rules for 3 cities in Suffolk County, New York.
Verified from official government sources
Accessory apartments (ADUs) are legal in every Suffolk County town under varying rules. Most towns require owner-occupancy of the primary dwelling, a minimum lot size (often 7,500-20,000 sq ft), a rental permit, and one off-street parking space for the ADU. Internal conversions and attached ADUs are most commonly permitted; detached ADUs are more restricted.
Small sheds under 100-144 square feet are generally permit-exempt in Suffolk County towns but must still meet setback rules (typically 3-5 feet from side and rear property lines). Sheds over 144 sq ft or those on permanent foundations require building permits. Electrical or plumbing connections always require separate permits.
Converting a garage to living space in Suffolk County requires a full building permit, zoning approval, plan review, and Suffolk County Department of Health Services sign-off if septic is affected. Converted space must meet R-3 residential code: egress, ceiling height, insulation, smoke/CO detection, and heat. Replacement parking must usually be provided.
Carports in Suffolk County are treated as accessory structures and require building permits in most towns regardless of size because they have a roof and foundation connection. Side-yard and rear-yard setbacks apply; attached carports must meet principal-structure setbacks. Tent-style fabric carports are often prohibited as primary vehicle storage.
Tiny homes in Suffolk County face significant hurdles. Towns require minimum dwelling sizes (often 600-750 sq ft), and tiny homes on wheels are classified as RVs and cannot be used as permanent residences. Fixed tiny houses must meet full NY Residential Code including Suffolk DHS septic approval.
3 cities in Suffolk County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
See every category we cover for Suffolk County — parking, noise, fences, fires, animals, pools, and more.
Suffolk County Ordinance Hub →