Plumbing and electrical cables are fitted into the polystyrene on the inside of the walls, after the walls and roof are completed. The polystyrene is easily grooved back to the concrete core to allow plumbing pipes and fittings to be installed, prior to the erection of plaster sheeting.

Some electricians, who like a wider space around the electrical cables, use a heat gun to melt a 75mm gap in the polystyrene. Both plumbing pipes and cables are run in the ceiling, then placed so that they run vertically down the walls, directly over the fittings.