1. It is not you who need to take any legal steps. It is for the  complainant and builder to initiate any legal proceedings if they can.
2. Extension of grill to the extend stated is not a causing any change to sanctioned plant of construction or causing any threat to structure of the  
3. There is nothing much they can do. Doors of courts are open for all. They may approach any court and tray to obtain some order but it is difficult get any order against you unless they file some case with fabricated allegations.
4. In all probability they may issue a lawyer's notice asking you to remove the grill, you can immediate file a caveat petition in the  Court they are likely to approach so that no order is passed behind your back submitting false facts to the  
5. All constructions will have such grills, no law is violated by you.
6. Wait for them to act, you can appropriately react to them.

1) remove the potted plants placed by you 

2) Fixed Boxed Grills are deemed illegal by Mumbai’s fire department. Fixed grilles, though aimed at keeping out robbers, are illegal as windows are supposed to be open and accessible for safe passage of people in the event of a fire.

3) apply for and obtain permission from local municipal corporation office 

If such an extension of the balcony of the flat deviates from the approved building plan then it is impermissible and not allowed either by the Builder or the Society.

However, a temporary arrangement may be made subject to permission of the Society or Builder.

The flat owner has no right to construct any kind of permanent structure without obtaining prior permission or approval from the concerned authority.

He has to prepare a modification plan and present it to the concerned authority for its approval.

Therefore your builder is right in asking you to remove the extension put up by constructing a grill.

The oral permission granted by the builder will not be an evidence or a approval to your this situation.

You ensure no water leakage to her flat due to the grill you don’t have to remove it 

- As per rule ,no structure  of   any  kind  whatsoever  temporary  or   permanent  shall  be  erected  or fence/partition  put  up  on  any common  area  that  may  obstruct,  or  impede  free movement in the event of an emergency of any kind. In addition, on the Limited Common Areas adjoining the ground floor flats 

- Further, anything that alters the facade of a building is generally not approved unless expressly permitted by the municipal corporation or the society.

- If the said box grill is not an alternation in the building and of common area , then the builder and the said neighbor has no right to dictate for the same. 

- You can give an explanation to the builder that only society has right to interrupt the same and not the builder 

- Further, you can take permission of the same from the municipal corporation. 

Since your building has not yet been converted into a Cooperative Housing Society (CHS), the builder still holds authority over structural modifications. However, here’s how you can handle this:

Legal Standpoint

1. 
   Municipal Rules (NMMC Regulations) – Any grill extension beyond the approved plan may be considered unauthorized. If it obstructs common areas or affects aesthetics, the builder or local authorities can object.
2. 
   Builder's Permission – Since you had prior permission, check if it was in writing. If yes, the builder cannot arbitrarily revoke it unless mandated by civic authorities.
3. 
   Neighbor’s Complaint – Water dripping is a nuisance issue, but if resolved (as you proposed), they cannot legally force grill removal.

Next Steps

1. 
   Communicate in Writing – Send an email/letter to both the builder and neighbor, stating that you have taken steps to prevent water leakage and requesting clarity on legal grounds for removal.
2. 
   RTI to NMMC – File an RTI with Navi Mumbai Municipal Corporation (NMMC) to check if such grill extensions are permitted in similar buildings.
3. 
   Wait for CHS Formation – Once a CHS is formed, members can decide on uniform rules regarding grill extensions, reducing the builder’s control.
4. 
   Legal Action (if pressured) – If the builder forces removal without municipal objections, consult a local lawyer for an injunction or relief.

If no official demolition notice is issued by NMMC, you are not legally bound to remove the extension. Stand firm and request written justification from the builder.

For detailed, personalized advice, consider a phone consultancy. Hope you find the information helpful. You are free to contact me for further discussion. If you could spare two minutes of your time to write a review, it would be greatly appreciated and bring immense happiness to read it. Thank you. Shubham Goyal.

Dear Client,

First of all, you have obtained the builder's permission at the time of the extension and have been using it for several years. Hence, you could argue with strong reasons that the extension is legal and should not be removed. The neighbor's problem about dripping water from potted plants can be sorted out by taking remedial measures, such as placing a sheet and diverting the water, but the problem of the removal of the extension in all sounds on the higher note. Besides, since the structure has not yet been assigned a cooperative housing society status, the builder's current request for the extension to be torn out might not hold any important legal oppositions unless local municipal rules guarantee it. It should also be checked whether the builder's original permission or other evidence of similar extensions in other societies can be gathered. Please consult with a property lawyer to review your particular case and arrange for mediation between concerned parties while ensuring that you are protected in your rights without having to redo your work.

Hope this helps. Please do not hesitate to reach out for any further legal queries.