If you are on the ground floor how is the question of terrace arising?
I do not know about the validity of your ownership of the garden. I know the rules and procedure in Greater Mumbai Municipal Corporation. Rules and procedure at Vasai-Virar also may be the same. At first you have to apply to your Co-operative Housing Society on plain paper and request them for a No Objection Certificate. Then you have to apply to the Establishment Department of the Municipal Corporation along with the NOC from the Society. The inspector from municipality should come and inspect the premises and give report to the Municipality. Depending on the report the Municipality may or may not give you NOC.
Sometimes the Society may refuse NOC. If so you ask them to give it in writing with reasons. If the Society does not give NOC, you can greese the palms of the Municipal staff and get NOC. At first you will have to greese the palms so that they send the inspector. The inspector may or may not come. He may dilly-dally. He will come if you greese his palms. When he comes to you for inspection greese his palms over a cup of tea so that he gives a favourable report. Again go to the Municipal Office and play all the tricks to get their NOC.
There is also a third way of doing things. You just go ahead and construct the weather shade. For the purpose of an excuse you apply to the Society for NOC. They will not give you written reply. So you go ahead.