Grade-II (A&B) is defined as:[8] Buildings, of regional or local importance, possessing special architectural or aesthetical merit, cultural or historical value, though of a lower scale than in Heritage Grade.

As per the defined "Scope for Changes (Grade-IIA)", the restorations permitted are:[8] Internal changes, and adaptive reuse will be generally allowed, but external changes will be subject to scrutiny.

The "Abbreviations of Criteria (Classification)" used for listing of buildings and conservation areas are:[8] a) Value for architectural, historical or cultural reasons A - architectural A(arc) - historical A(his) - cultural A(cul) b) The date and / or period and / or design and / or unique use of the buildings or artefact B - period B(per) - design B(des) - use B(uu) c) Relevance to social or economic history C (seh) d) Association with well-known persons or events D (bio) e) A building or groups of buildings and / or areas, of a distinct architectural design and / or style, historic period or way of life having sociological interest and / or community value E - Style - Historical f) The unique value of a building or architectural features or artefact and / or being part of a chain of architectural development that would be broken if it were lost F g) Its value as a part of a group of buildings G (grp) h) Representing forms of technological development H (tec) i) Vistas of natural / scenic beauty or interest, including water–front areas, distinctive and / or planned lines of sight, street line, skyline or topographical I (sce) j) Open spaces sometimes integrally planned with their associated areas having a distinctive way of life and for which are and have the potential to be areas of recreation J In keeping with the above categorisation, the restoration works of the Municipal Corporation Building, Mumbai was planned by a panel of three conservation architects, namely, Abha Narain Lambah, Shashi Prabhu and Shimul Zaveri Kadri.

[8] In the first phase the structure would be restored to its original glory involving replacement of broken tiles, repair of statues, and removal of plants and moss.

[8] The subsequent phases of restoration would involve a) reorganisation of office space within the building to improve the operational efficiency of staff members, b) 'Citizens Facilitation Centre' and party offices in the ground floor and c) Corporation Hall to be modified for a larger seating arrangement by including outer corridors and opening the wooden doors to increase its seating capacity from 200 to 300.

[7][10][11] In the period from 1100 to 1500 AD, the architecture of churches constructed with ornamental arches, with ribs supported by buttresses resulted, in the subsequent idea of the framed structural design with grandeur and monumentality during the renaissance period of 1500–1700 AD, as the distinct style; the Mumbai Municipal Corporation building, Chhatrapati Shivaji Maharaj Terminus, the Rajabai tower and the University of Mumbai are some examples of this style.

[12] The Gothic architecture with controlled composition custom–made to the climatic extremes of the city has cusped window arches and elaborately domed corner towers.