Four building collapses reported in just nine months in the city have called for immediate attention toward what caused the crashes, threatening the lives of many.
Use of inferior quality construction material and tampering with the load-bearing pillars are some of the known reasons that bring a building down, as seen in the September 27, 2013, Dockyard Road building collapse, which killed 61.
According to experts, the practice of lowering the plinth level (the top side of a building's foundation) arbitrarily to gain additional area or construct a loft is an equally threatening factor. They, however, added that none of the four collapses were caused due to this. "To gain additional space/volume, people engage in such a practice sometimes. Unknowingly, they chop structural members, such as plinth beams. Once the structural members become slender, a building becomes vulnerable," said Chetan Raikar, chairman and managing director of an engineering consultancy firm, Structwel. Plinth beams are located beneath ground surface.
Raikar, a structural engineer himself, said weakened beams pose more threat to a building's safety during earthquakes.
Another city-based structural engineer, who did not wish to be named, seconded Raikar but said alterations to plinth level can be made but only in the presence of experts and with prior permission from the Brihan mumbai Municipal Corporation (BMC). He claimed that lowering the plinth level may not necessarily always weaken a structure but hurting structural members can. "Untoward incidents occur because alterations are made without the BMC's knowledge or supervision of licensed surveyor or structural engineers," he said.
He, however, expressed concerns over the lowering of plinth level arbitrarily being considered as just another illegal alteration. "The punishment for making illegal changes is not a deterrent. The BMC can act only through courts. Harming plinth beam is a serious issue vis-à-vis the punishment given," he said.
Often, the indifference of the local ward office to complaints about lowering of plinth exposes the buildings concerned to danger. For example, in M-west ward, the plinth of Peace Haven building on 18th Road, Chembur, has been lowered by a shopkeeper. An MRTP notice was issued to him, but no further action has been taken. The building, meanwhile, continues to remain vulnerable. Several restaurants, such as Peninsula in Sion, have majorly lowered the plinth level and created rooms below.
Despite repeated attempts, municipal commissioner Sitaram Kunte and chief engineer (development plan) Rajiv Kuknur did not respond.
DCR, 1991, state...
Plinth means the portion of a structure between the surface of the surrounding ground and surface of the floor immediately above the ground
The minimum plinth height must be 30cm. In areas subject to flooding, the plinth must be higher than the high flood level
In case of illegal alterations, the BMC can issue a notice under section 53 (1) of the MRTP Act, 1966, for making alterations without permission. However, one can apply for regularising the changes within a 30-day period. The BMC can process application for regularising under section 53 (3) of the same. If no application is made, the civic body undertakes demolition. Maximum punishment (under section 52) is jail up to six months or fine. Under the MMC Act, 1888, action is taken under sections 351 and 354, which also allow regularising a structure. Section 471 lays down punishment of a maximum jail term of three years and fine not above Rs5,000