1. firstly you accepted possession without OC in place. This itself is a violation of law as no premises can be occupied until OC is received for the same
2. secondly the bungalow is allotted to you on ownership basis, i presume, and not on lease or tenancy or license
3. so once a property is allotted on ownership basis, then i fail to understand how the builder can object against the owner when he wants to deal with the same in any manner he deems fit, so long as the owner complies with the local municipal laws
4. so if you want construct your personal pool in the space which is allotted to you on 'ownership' basis and you also have the requisite approval from the municipal body for the same, then the builder does not have any business to object against that
5. you also need to check your sale agreement if there is any clause therein which restricts you from altering the space allotted to you. Even if there is any such clause, in my opinion, it is nothing but a blanket consent of the purchaser. Once the property is allotted on ownership basis, there cannot be any restriction, subject to compliance of local laws
6. ownership right is a bundle of rights which includes the right to make changes to the property, ofcourse subject to compliance of local laws
7. so i suggest if your builder is objecting against you building a private pool, then question him on what authority or basis he is doing so
8. issue him a legal notice and also remind him to obtain OC. Do inform the builder in the legal notice that you have obtained prior written permission of the local body to construct the private pool in your plot
9. I guess Lonavla has a Municipal Corporation and so you will be required to take its permission for building the private pool