Yes, the civic body will not take any action, if the beams and load-bearing walls on which the structure stands, are not modified. Changes can be made, without touching the foundation of the building. However, any interior repair work that may harm the building structure, will not be allowed.
Hi Shekhar, Your local authority will be able to advise you about this. Generally, you will not need planning permission for. Building an extension to the rear of the house which does not increase the original floor area of the house by more than 40 square metres and is not higher than the house.
I am agree with Nitesh. The extension should not reduce the open space at the back of the house to less than 25 square metres which must be reserved exclusively for the use of the occupants of your house. If your house has been extended before, the floor area of the extension you are now proposing and the floor area of any previous extension (including those for which you previously got planning permission) must not exceed 40 square metres. (There are also other height restrictions.)