Building Plan

Not advisable.  As the construction is not as per the approved plan it is always going to be a problem for you in future. 

1.  In a  Civic Body jurisdiction and Town Planning Dept.   "ONLY & ONLY"  a    "SANCTIONED Plan"  is a legally approved plan.  Everything else is   "illegal & unauthorised".

2.  Payment of  "EB, Water and Property Tax"  etc.... whatsoever, does not grant  "legallity" to the  non-approved  non-sanctioned building.

3.  Make a written complaint to the  local Municipal Corporation, describing the  "illegal & unauthorised" structures, and attach the recently obtained certified copy of the  "approved plan". and request for demoliation of the same.   If the civic body refuses to demolish the same,  file a Writ Petition (writ of mandamus) in the chennai HC, praying for directions to the muncipal coporation to do the needful.

4.  For   "illegal & unauthorised"  constructions,  the Law of Limitation does not apply.  Hence any possession of "illegal & unauthorised" constructions is  invalid and illegal.

Keep Smiling .... Hemant Agarwal

Agrawal has rightly told you relevant provisions of law and you may also study the case of Delhi where MCD demolished all such illegal constructions even after 75 years of such constructions.

only approved plan by competant authority is legal one. pls ask builder wether he has made any application for approval of another floor? or when it will be approved. but without approval do not purchase a property