Luiz- Ensure that you are using corrugated metal decking, and pour high quality concrete within a form involving that decking, to at least 6" in depth. Also, form a grid of epoxy-coated 1/2" rebar consisting of 1' x 1', 1" off the bottom of a top rib of the decking. Ensure that the concrete is air-entrained and fibre-reinforced. 25 mpa. Pour it flat, and don't forget to mechanically vibrate. The span of the ribs may be no longer than 8'. The seams of the decking must be crimped, and welded. The rebar must be tied with epoxy-wire. After all that, install Blueskin and then insulation and then gravel base! Voila, si simple :)

Ensure that you are using corrugated metal decking, and pour high quality concrete within a form involving that decking, to at least 6" in depth. Also, form a grid of epoxy-coated 1/2" rebar consisting of 1' x 1', 1" off the bottom of a top rib of the decking. Ensure that the concrete is air-entrained and fibre-reinforced. 25 mpa. Pour it flat, and don't forget to mechanically vibrate. The span of the ribs may be no longer than 8'. The seams of the decking must be crimped, and welded. The rebar must be tied with epoxy-wire. After all that, install Blueskin and then insulation and then gravel base!