A lot of times and in many circumstances, homeowners while doing renovation may not know that they have put in structures or made modifications to their home that are not in compliance with the code of the local building departments. 

These structures may be a finished basement, a renovated bathroom or kitchen, a new interior wall etc. are therefore “illegal” and in violation of the local building code.  Legalization is the process in which a professional such an architect assess the violations, consult with local building department and the code, and work with the homeowners to rectify the violations by removing or modifying the existing structure so that it complies with the code. 

When all violations are rectified and inspected by the local building department, a certificate of occupancy will be issued to the homeowner signifying that the structure in question complies to all local codes and is therefore legal to be occupied.

It should be noted that during the legalization process, there may be numerous permits or inspections required by the local department before the final certificate of occupancy is issued.