Leavy of service tax on labour supply for construction work.

All depends upon the terms of your contract with the Company :

1.  In case the Suprientendance & Control over labour rests with the Company then you (being an individual) will be liable to pay service tax on 25 % Value @ 12.36 %

2.  In case the Suprientendance & Control is excercised by you then NO reverse charge is appicable, in this case you need to pay service on 100 % Value @ 12.36 %

From your query it seems you are just supplying the manpower to the Company having no control over the "labour"  if this is so you need to pay service tax on 25 % value.