In Slab

Floor Style – In Slab Hydronic Heating

In slab Hydronic floor heating is a storage heating system. The slab is heated by pumping hot water through pipes laid in the concrete slab. This process can take one to two days at the beginning of the winter season, depending on the thickness of the slab and the amount of floor insulation used. Once the slab is heated through, it radiates heat up into the room creating a comfortable environment with no draughts, no dust and no noise.

We install the Hydronic heating pipes inside the construction slab prior to the slab being poured. We clip our piping to the re-enforced metal bar a specific distance from the top of the finished surface. This is critical to the performance of the hydronic heating systems to enable an even heat spread up through the slab. To time this properly and ensure a smooth and successful installation involves close communication between us, the builder, engineers and the concreting contractors.

The pipes used are cross linked polyethylene (PEX) pipes developed in Europe specifically for under floor heating. PEX pipes are extremely tough. They are connected with leak-proof compression sleeve fittings and there is an oxygen barrier applied to the outside of the pipes. We use German made Rehau® pipes that come with a 25 year warranty.

Typcial In Slab Construction


There is only limited zoning available with in slab heating systems. You can zone the back or front of the house, but you are not able to set different temperatures in different rooms. The nature of in slab heating is to heat the entire slab so the concrete becomes a large thermal mass, radiating heat upwards. This makes it impossible to have different temperatures in different rooms because they all share the same thermal mass (ie the slab floor)

It does take a fair amount of time and cost for the boiler and pipes to get the entire construction slab up to temperature, so this system is usually left on all winter. To manage heat the thermostat is simply turned down, but not off, at times when not needed or on warmer days, as opposed to turning the entire system off and on again. This style of Hydronic heating is very efficient through long periods of cold temperatures and is popular in very cold climates. It also works well though the colder times of a Melbourne winter, however through spring and autumn where temperatures change from day to day, the warm up delay and cool down times are worth noting.

*We recommend extruded polystyrene insulation beneath the slab and on exposed slab edges to minimize system heat losses.



  • Residential, commercial or industrial
  • Slab on ground or suspended slab

  • Pipe laid over top layer of reinforcement
  • Minimum 30mm cover over top of pipes (50mm recommended)
  • Pipe external diameter of 16mm typically used for residential applications