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Under slab

If pipes are laid under the slab they should be located wholly under the slab where possible. Extra bottom mesh should be placed over the pipe to avoid any weakening of the slab.

Box-outs for bath, shower bases and similar plumbing fixtures should be placed carefully to minimise weakening of the slab.

Note: Electric heating cables may be embedded in the slab without any increase in thickness or reinforcement.

Diagram of a section of a pipe under slab. The thickness of the slab is 100 mm, the layer of bedding sand is 50 mm and the pipe runs through a layer of bedding sand.
Section showing pipe under slab
Photo of a box-out for a bath.
Box-out for bath