Underfloor Heating Floor Types

Concrete and Screed Floors

In general the insulation goes down onto a concrete slab or oversite.

The concrete slab or oversite must be level with a tolerance of no more than +/-6mm on a three metre straight edge. The floor should be clear of dust and debris before laying the insulation.

An edge insulation is applied to all walls. This prevents heat migrating through and up the walls.

Fixing the Pipes Down

There are three different methods of fixing a pipe to insulation board:

• Lay mesh down and fix pipe to it with cable ties (A142).
• Lay clip rail and insert pipes and designed centres.
• Staple pipe directly onto purpose made insulation board.

Timber Suspended Floors

There are several methods of installation in suspended floors. Apart from notching requirements, the pipe and plate installation methods are the same for both methods.

The two main methods are:

• Counter battening
  If the floor can be raised by 25mm the best method is to counter batten with a minimum of 75x25mm battens on top of and at right angles to the joists at 300mm centres. Counter battens should not be run or be fixed right up to the walls, as the pipe needs to be looped under them.
• Joists at 400mm centres
  If the floor cannot be raised (usually the case in existing buildings) the system has to be laid flush with the top of the joists. If the joists are not at 400mm centres then an arrangement of battens is necessary to allow the UFH to be laid at 200mm centres.

Insulation

It is essential that there is a minimum 100mm of insulation between the joists, as close to the underside of the plates as possible, even on intermediate floors. The insulation should be laid before battening.

Counter Battening

Battening should be done before the UFH installer begins work. Battens should be a minimum of 75x25mm and laid at right angles to the joists at 300mm centres. Battens should be nailed to the joists except at the last two joists against walls. This allows the batten to be lifted slightly to tuck the pipe loop end under the batten.

Heat Emission Plates

Heat Emission Plates are only for heat distribution. They are not structural. They are easily damaged and it is very important that no other trades are allowed where the UFH is being installed. The number of plates allowed for each room is shown on the computer print out and also on the drawing.

Plates should be laid unfixed across the floor before securing. Laying too many plates will result with a short fall in the final stages of the project. Laying too few plates will result in insufficient heat diffusion. Plates should never touch each other. Plates are only laid under straight runs of pipe.

View the demonstration video: