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Weber Saint-Gobain - Official website of the company

Under-Floor Heating


Substrate preparation - depending on substrate:

  • Cleaning
  • Rough levelling of the substrate for installing the system plates or optional additional installation layer EPS-plates.

The surface in general has to be dry and free from surface contamination and other impurities. All dust and debris should be vacuumed from the surface. Smaller holes and floor irregularities, such as prefabricated elements and height differences, can be smoothed out with bagged sand to ensure the stable application of the heating plates.

Optional installation layer

This optional layer can be used for sewers, water pipes, electrical installations or any other requirement for an intermediate layer.

Small installation needs are conveniently dealt with using a 30-50mm layer of EPS boards into which 'omega shaped' grooves are cut with a heat cutter.

Where there are several pipes, it is more convenient to make a complete duct and to tie down the group of pipes. The gap is filled with thick flowing mortar or screed to form a uniform support for the system plates.

Pipes can also be drilled down through intermediate slabs and be led in the suspended ceiling below or through self-bearing base floors.

Heating pipes

Heating pipes made of PEX or composite materials are common. To achieve a high efficiency at the windows, start the heat circuits at the perimeter walls. The areas close to the central heating and at pipe joints should be fixed to corner plates.

The ingoing water is usually ≈ 23-30°C and the returning water cools down approx. 1-4°C. The heating designer calculates these temperatures and the ingoing water temperature is usually adjusted with an outdoor thermostat, whereas the circulation per room is regulated by room thermostats.

The length of the pipe circuits, the pump's pressure, the room area and the used floor covering material also affect these temperatures. Therefore, the heating design is carried out by professional heating designers.

Dividing layer

Geotextile separates the fresh screed from the heating system below and stops the screed flowing in between the insulation boards. Geotextile is carefully selected for its resistance to leaks and its workability guaranteeing a rapid and secure final result. The Geotextile is rolled out on to the plates. Connecting parts are taped and the dividing layer is applied to all vertical construction elements. This ensures that materials added subsequently cannot run behind them.

Surface slab

Before the surface slabs are installed, weberfloor 4945 glassfibre mesh must be laid out in preparation for a cement-based screed. When laying out the mesh, ensure that the edges overlap by 50mm. If a calcium sulphate screed is used, no reinforcement mesh is needed.

As a load and heat distribution layer, three different self levelling screeds can be used within the Comfort Floor Concept:

weberfloor 4360 base flow rapid - An economical fibre reinforced cementitious base screed, designed for floating floors up to 80mm thickness. The minimum thickness is 25mm offering a sufficient point load capacity and a good sound reduction at moderate costs. If PVC or linoleum is to be used, grinding and manual smoothing will be needed.

weberfloor 4310 fibre flow or weberfloor 4320 fibre flow rapid  - A fibre reinforced, flexible cementitious screed with high polymer content. Recommended if PVC or linoleum is used and when separate hand smoothing needs to be avoided (light grinding is still recommended due to the high fibre content). The minimum thickness is 25mm and the maximum thickness is 50mm.

All materials are pumped directly on to the Geotextile in the recommended thickness and are levelled by wobbling the fresh screed.

NOTE: Pure Portland cement-based screeds or concrete are not suitable for the Weber Comfort Floor, due to the aluminium reacting (vaporizing) with the high pH of the humid concrete!

Further recommendations

The floor covering may be applied once the drying conditions are suitable. The indications referring to the readiness for covering apply to a dry substrate, a room air temperature of 20°C and a relative humidity of 50%. Air dehumidifiers, draughts and too high temperatures must be avoided.

Normal apartments can usually be done without any joints. In the case of unfavourable geometry (narrow long corridors or big areas where the uniform slab is "cut" by partitions), we recommend creating a "dummy joint" by cutting the slab approximately 5mm deep at such critical places. If the slab is to crack, it will crack in a controlled manner at these places but it will still be held together by the glassfibre mesh. If the floor covering requires a joint, and a crack-free floor is required, these dummy joints can be injected as soon as the shrinkage stresses have ceased, i.e. when the screed material has dried out completely!

As the heating pipes are completely below the screed slab, the risk of damaging these when cutting the dummy joints is very small. Also, the heat pipes will not suffer from the screed slab having any joints as they are not embedded in the screed.

Expansion joints do not have to be used as the surface slab floats completely freely, independently of the building. On the contrary, we can offer seamless floating screed floors which also enable the tiling of large areas without joints and cracks.

Please note that small hair cracks may occur due to the building shape or the substrate. These are purely optical flaws and have no influence on the floor's adhesion or loading capacity.