Guidance  40A Existing Uses, Permits, Nonconforming Property and Lots

Date:	09/18/2026
Organization:	Executive Office of Housing and Livable Communities
Referenced Sources:	Section 42. Housing Production - Permit Protections Section 43. Housing Production - As of Right Extensions for Nonconforming Lots 1 Section 44. Housing Production - As of Right Extensions for Nonconforming Lots 2 Section 45. Housing Production - As of Right Extensions for Nonconforming Lots 3 Section 46. Housing Production - As of Right Extensions for Nonconforming Lots 4

The law expands protection for pending entitlements, creates a limited as of right path for certain nonconforming properties, lengthens the building-permit protection period and the abandonment period, and expands protections against merger for commonly owned adjoining lots.

Pending permits and other entitlements

These amendments broaden G.L. c. 40A’s protection from later zoning changes from only applying to building or special permits that were already issued to now include any such permit or other entitlement applied for under Chapter 40A before the first publication of the hearing notice for the zoning change. 

Certain nonconforming structures and residential uses

A pre-existing nonconforming structure or residential use may be extended or altered as of right, without the “not substantially more detrimental” finding otherwise required by Section 6, when both of the following are true:

• The nonconformity results from lot size or shape, frontage, lot coverage or floor-area-ratio requirements; and
• The proposed extension or alteration complies with current requirements for height, number of stories, and setbacks.

Note that this change only removes the Section 6 detrimental-effect finding for qualifying extensions and alterations. Other applicable zoning provisions, permits, building-code requirements, and non-zoning approvals are unaffected.

Protection for work under a building permit

• The amendments extend protection from zoning changes for issued building permits from 12 months to 24 months.
• The 24-month period runs from the issuance of the last permit necessary for construction.
• The 24-month period is paused while the applicant is actively seeking or obtaining other necessary permits.

These rules relate only to the protections provided under Section 6. 

Special permits, site plan approvals and abandonment

The requirement for work under a special permit or site plan approval to commence within three-years of issuance has been retained. The existing rules for previously disturbed land and phased development also remain.

The period that local zoning may use to define or regulate an abandoned nonconforming use or structure increases from two years to four years.

Protection for certain existing lots (Pre-existing nonconforming lots)

Section 6 protects two categories of lots from later increases in local requirements for lot area, frontage, width, yards or depth:

• One protection applies to a qualifying lot that was not held in common ownership with adjoining land when it was recorded or endorsed, complied with the zoning then in effect, and has at least 5,000 square feet of area and 50 feet of frontage.
• The other provides five years of protection for up to three qualifying adjoining lots held in common ownership. Those lots must have been recorded or endorsed, complied with the zoning requirements in effect on January 1, 1976, and have at least 7,500 square feet of area and 75 feet of frontage.

Application of these protections was previously limited to lots for single- and two-family residential use. The amendments remove that limitation such that all lots that meet the above conditions qualify for protection. All other eligibility requirements remain in effect. The amendment does not, by itself, authorize land uses prohibited by the municipality’s zoning ordinance or by-law.