More about pipes in the slab?

Cashmere project 2018 grand prize winner's

Let’s take a look of the example of our 2018 grand prize winner – Martin& Lynn’s project. How do we put the pipes in the slab? How do we actually do it? What is involved? 

  • The grand prize covered $5,000 (incl. GST) worth of the cross linked Pex-b pipes supplied and installed (stapled directly onto the polystyrene) in the foundation.

It’s a nice flat section in Cashmere, Christchurch. They have chosen a fully insulated slab supplied by MaxRaft.

Why fully insulated?

Underfloor heating has turned our concrete slab into a huge energy storage, which is great to maintain the warm home through the winter. By insulating the whole slab(especially the edge of the slab) heat loss is reduced and running costs are lowered.

Related report by BRANZ: BRANZ SR352 Perimeter Insulation Of Concrete Slab Foundations

Usually we will lay the pipes directly onto the polystyrene before the mesh goes down. This means the pipes do not interfere with any saw cuts or reinforcing steel.

Related article: To mesh or not to mesh?

All the pipes leave and return to a manifold, which is often placed in the linen cupboard. underfloor system is closed loop and completely seperate to the potable water supply, therefore cross contamination is not possible.

The system is pressurized with air and monitored throughout the building process. In the unlikely event a pipe is holed, rectification is straightforward.

Once the floor pipes are installed, normally one to two days work, the builder can install the mesh.

Here is a video of a concrete pour.