Middlesex County, MA Permit Requirements: Shed & Outbuilding Permits (2026)

The Massachusetts State Building Code (780 CMR), based on the International Residential Code, applies uniformly across all Middlesex County municipalities. Under 780 CMR, one-story detached accessory structures used as tool and storage sheds, playhouses, and similar uses with a floor area not exceeding 200 square feet do not require a building permit. This exemption assumes the shed does not include plumbing, electrical, or mechanical systems. Even exempt sheds must comply with local zoning setback requirements — these vary by municipality and zoning district but typically require 5–10 feet from property lines. Some municipalities (Cambridge, Somerville, Watertown) have tighter setback requirements due to smaller lot sizes. Sheds over 200 square feet require a building permit from the local building department. Plans must show structural details and compliance with setbacks, lot coverage, and the building code. In flood zones (areas along the Concord, Assabet, and Charles Rivers), sheds may need to comply with FEMA and local flood plain regulations. Municipalities with historic districts may require Historic District Commission review for sheds visible from public ways. Pre-fabricated sheds (resin, metal, wood) under 200 square feet can be placed without permits but still must meet zoning setbacks. Some municipalities require a zoning permit even when a building permit is not required — check with your local building department.