I agree with mr. dubey and also request you to go through s.no. 12 of the table annexed to notfn.no. 26/2012 which also talks about abetment of value on complex construction services of 75%.
It is all confusing in service tax.
The central govt must come out with immediate clarification so that minor repairs upto Rs.30000 per bill are not covered in service tax. This reverse charge mechanism has just been added without giving any thought to the misery which it will cause to small and petty traders. Sometimes it looks that they did it just to save advocates from this service tax registration. The time has come when the govt drops any idea of discrimination between advocates and other professionals.
Perhaps they have covered everything under the sun in the definition of "works contract" if it is not covered by any other term.