After the roof is on and the house is at lock-up stage, the plumbing and electrical cables can be installed in the walls by grooving out the foam on the inside of the walls and placing them into the grooves.

Plumbing fittings can be fixed back to the concrete core, and electrical cables are left protruding through the plaster sheet at the appropriate points.

Plaster sheet is fixed over the walls, covering the plumbing and electrical cables.