The first query that arises in people’s mind, when they hear the news of building collapse is,
“What is the age of the building that collapsed?”
Everyone assumes that age may be the reason for building collapse. But sometimes building may fail at the time of repairing or restoration/renovation even not very old.
Here we discuss how the building collapses during the repairing or restoration/ renovation:
The building collapses when you play with configuration of structural system i.e. if remove RCC elements particularly column without alternate supporting system or say remove load bearing wall.
Repairing/restoration or renovation of building is the action of recovering the original state and strength of building as it appeared, and had early in its history without affecting the heritage value. The repair and restoration/renovation work is performed to recover the damages to building over the years. Buildings collapse due to many reasons but it is more common during repairing or restoration/renovation, and mostly due to illegal alteration, or unauthorised construction carried out in the building.When the plan of house or building is changed, it means the construction differs from the original approved plan; It is considered as illegal alteration or unauthorised construction, which mean either you are subjecting building to additional load or are trying to change load path of the building. Both are equally dangerous.
Why Repairing or Restoration/Renovation is the Reason of Collapse of Building?
Repairing becomes necessary when the older elements loose their strength due to wear and tear on aging, or say there are cracks, sometimes repairing is also simultaneously done when you modify the design or add to the building for your changed needs.
The owner adds rooms, construct or demolish walls, or alter the layout of the building during the repairing or renovation of the building. These alterations develop uneven stresses in the building, and hence unthoughtful alteration or construction without consulting structural engineer may invite building collapse. The repairs like plastering, tiling and painting can be done without permission of structural engineer, but when you add rooms, construct or demolish walls, or alter the structural configuration of RCC member, it is necessary to consult the structural engineer for its overall behaviour safety, and stability purpose.
The major reason for building collapse is the change in the direction/path of load path building without consulting the structural engineer. i.e. removing RCC column or load bearing wall, repairing of old and damaged column without adequate propping, increasing size/strengthening of RCC elements, addition of stories on old building, or when columns/walls are put not one above other, repairing or constructing foundation near the adjoining building.
Please note that the failure of column invites sudden collapse of building, while in case of a failure of slab or beam, it will give you time for repairing, providing supports, etc.
Sometimes the repairing and restoration work may require the partial or full dismantling of the RCC elements. The dismantling of the structural members like column, beam-slab without establishing proper alternate supporting system disturbs the adjoining structural members and bring about failure. These disturbances affect the stability of adjoining structural member and hence it may cause partial or total building collapse.You will need proper supports of props preferably MS (not wooden) to safely transfer the load. Do not remove the props, shuttering supports until the re-strengthened elements have acquired the desired strength.
In conclusion, to maintain homogeneity and integrity of the building, it is essential to keep the structural elements like columns, beams and slabs in the as-built position. One cannot remove or alter the size of the structural element for decoration or extension purpose. Such changes endanger the stability of the structure which can be the reason for building collapse. Never play with safety and stability of the building without consulting structural engineer. And of course, always employ experienced repairing contractor.