Applicability of service tax

I have a booked a flat in jan'10 on construction linked plan (CLP) My Ist demand was raised in May'10 when service tax was not applicable on residential complex. the builder raised the demand for payment of 40% of cost in may'10 & the payment was received by builder in July'10.

The service tax was made applicable on residential complex from July'10 hence what is the applicability of service tax on demand raised by builder in may'10. whether service tax is attracted on may'10 demand.