This is a very complicated issue that must be addressed on a case-by-case basis. The relevant law regarding this issue is Mass. General Law Chapter 40A, Section 6. Contact the Building Inspector/Zoning Enforcement Officer at 508-892-7003 to discuss what documentation you must provide to show that your property is “grandfathered.” This is often not a straightforward determination. Please note that you may be advised to contact a land use attorney to help you document your case.