Applicability of service tax

Tripti (CA Business) (25 Points)

03 November 2014  
I have one query related to aaplicability of Service Tax.
 
One of my client(Builder) purchase a land and handed over to contractor for purchase of Flats over there. Contractor completes the building and after that the same will be sold to customers. Each unit will comprises of 4-5 flats but during the year total flats will be 15-20 flats. So in this case whether the service tax will be applicable on contractor or builder. And if applicaple on anyone how the valuation will be done.
Please help