Works contract under GST?

SOIL TESTING,DESIGNING,ARCHTECTERS,VALUATIONS,DRWAING SUBMISSION,SUPERVISOREY

Sir,THE ABOVE ITEMS ARE COMING UNDER WORKS CONTRACT..NO MATERIALS WERE INVOLVED. SO PRESENTLY ONLY SERVICE TAX IS PAYING.. CORRECT..BUT WHAT ABOUT IN GST??WHETHER WE HAVE TO PAY BOTH.... IGST & SGST..TOTALLY IT WILL DOUBLE THE TAX% ????????