Tax Rate work contract on supply of services with material SAC code and rate

Pardeep Sharma (47 Points)

13 September 2023  
Work contractor making foundation of plant and machinery under supply of services SAC under chapter 99 and charging GST @ 18%

While he is using Cement @ 28% Bricks, Sand, Concrete @ 5%

Please clarify could he charge the Tax @ 18% ?
under which Rule ?
What would be GST HSN / SAC?
Should he use separate SAC and HSN ? or He can use only SAC in this case ?
Can we take INPUT of foundation space area 6' x 8' for BOILER AND INSTALLATION OF FORGING HAMMER under plant and machinery?