Massachusetts General Law, Chapter 40A, is the governing legislation that controls land uses. Part of the law is a fundamental requirement that variances of dimensional regulations may only be granted to parcels that meet specific conditions.
During the process of application for a building permit, a review and determination by the Building Commissioner is performed for verification of zoning compliance of the lot and any existing structures and proposed new construction.
If the existing structure does not fully comply with the present zoning regulations then the legal definition of the property is titled non-conforming. As a non-conforming structure rights such as a change of use or altering the building lines may require a finding of the Zoning Board of Appeals.
When the proposed construction does not comply with the local zoning regulations, a building permit may not be issued.
The City of Melrose, having recognized that a major percentage of the structures in the City are pre-existing non-conforming, passed an ordinance that relieves some dimensional deficiencies.