Boston, MA Environmental Rules: Flood Elevation Requirements (2026)

Boston Zoning Code Article 25A creates the Coastal Flood Resilience Overlay District (CFROD), mapped over the areas the city expects to face future coastal storm flowage or tidal action from sea level rise within roughly the next 50 years. 1(a) sets the Sea Level Rise Design Flood Elevation (SLR-DFE): it cannot be lower than two feet above the Sea Level Rise Base Flood Elevation (SLR-BFE) in a FEMA Coastal A, V, or VE zone. Outside those zones, the margin is still two feet where any part of the lowest occupiable floor holds a Residential Use, an Essential Facility, or a High Risk Structure as defined in the Massachusetts State Building Code, 780 CMR, and one foot for everything else.

1(b) forbids Residential Uses entirely below the required SLR-DFE, with narrow accessory exceptions for vertical circulation (lobbies, stairs), Flood Protection Equipment, storage, and parking. The Article reaches large projects: under Section 25A-4, it applies to projects adding 20,000 or more square feet of gross floor area outside the Harborpark (10,000 within it), adding 15 or more dwelling units, changing use on 50,000+ square feet, or substantially rehabilitating a structure of 100,000+ square feet, and any smaller project may elect in. 2(a) also uses the SLR-BFE benchmark for maximum Building Height, measuring from whichever is higher: existing grade, or two feet above the SLR-BFE.

Historic structures listed on the National Register or designated by the Boston Landmarks Commission under Chapter 772 of the Acts of 1975 can seek a variance from the Board of Appeal for reconstruction or restoration work. 2 where the two provisions conflict.