Hi Sunil,
Based on the background of your case, i understand that your query is most specific only to the applicability of Service Tax in the instant transaction.
Considering the provisions of Service Tax law, Service Tax would be applicable on the said transaction to your service provider.
With respect to your builder's delay in charging Service Tax in his initial bill, I would like to point out that in the case of Max New York Life Insurance Co Ltd Vs Insurance Ombudsman and Others reported in [2013] 57 VST 514 (Ker), the Hon’ble HC has held that a service provider who does not disclose the prevailing statutory duties and levies at the time of transaction is not entitled to claim such taxes and levies from the consumer at a later stage during the course of continuing service.
Hence, you may deny to pay the Service Tax on the ground that he has not charged the service tax on the initial bill.