It forms part of common area for benefit of all flat owners 

you cannot carry on any construction on terrace without consent of other flat owners 

Unless and until right f construction is specifically gven to any of the flat owners with consent of other flat owners no construction can be made on roof of a building. 

It is a common area.

The other flat owners may not give consent or permission or NOC for you to construct additional structure in the terrace above your flat. 

If you still go ahead, a simple complaint by any aggrieved fellow flat owner would prompt the authorities to demolish the same. 

- As per the DDA policies the following alteration and construction is allowed on terrace of DDA flats:

1. A barsati of size equivalent to the room below is allowed ensuring the construction of wall over wall. However, other residents should have the access to the maintenance of water tanks, plumbing system and TV antennas, etc.

2. Covering of the open terrace with sloping roofs up to 9 feet high with light-weight material such as fibre glass/AC sheets/sheets/pipes and standard angle iron sections etc. and enclosing with glazing.

- Further, for any construction over the terrace , the permission of the DDA is mandatory. 

You can’t construct against your plan. You need permission for dda 

Dear Client,

The Delhi Development Authority declared that everyone has the right to use the common areas in DDA apartments, which include the complexes' roofs, terraces, and staircases. Common amenities, such as the roof terrace and the shared stairway that extends to the roof terrace, belong to all of the block's owners or occupants and cannot be used just by one or more specific residents or groups.