Underfloor Heating Floor Construction: Floating Floor

A guide to underfloor heating with a floating floor construction.


Floating floors for underfloor heating installation provide an ideal solution to the issue of time-consuming screed floor installation wherever time is of the essence. Screed flooring can take several weeks to properly dry out and set. Additionally, no further securing joists or battens are necessary when installing floating floors.


Construction of a Floating Floor

A floating floor installation can be constructed by layering a pre-formed, high-density, profiled polystyrene panel on top of either an existing floor or a newly constructed floor. Any pipework necessary for underfloor heating is laid within the grooves of the polystyrene panel, fitted into clips which should be inserted into the panel prior to the laying of the underfloor heating pipes. The clips and pipes should be flush with the level of the polystyrene boards once installed. Aluminium spreader plates may be used in conjunction with the pipes in order to more evenly distribute heat across a wider area of the floor. At this point, it is possible to apply an optional layer of screed directly above the polystyrene insulator and the secured pipework, in order to better diffuse the heat. A vapour barrier, or polythene sheet, is to be laid on top of the aluminium layer. The tongue-and-groove floor decking sections are secured to one another and laid immediately above the supporting polystyrene (which ought to have a minimum density of 15kg/m³ if expanded polystyrene, or 25kg/m³ if extruded polystyrene), but are not secured in any way to the previous layer – they are left to ‘float’ above it. Carpet may be applied above the decking.


Floor Height

The resulting height of a floating floor construction is most often dependent upon the final thickness of the insulation used. Despite the levels of  floor insulation which may prove necessary, floating floors most often do not reach heights as great as those of solid floors. However, building regulations may necessitate the use of extra insulation, raising the floor substantially.


Floor Temperature

Although the necessary water temperature with a floating floor is ordinarily higher (usually 40c-50c) than that used with a solid floor, the resulting temperature output of a floating floor will likely be lower than that of a solid floor, but should be more than comfortable even in the coldest months in a modern, well-insulated, double-glazed building: ordinarily the temperature will level at around 27c.



  • When installing underfloor heating with a floating floor construction with underfloor heating pipes, it is necessary to pressure test the pipes by filling them with water before laying the aluminium and final floor layers, thus allowing for any damage to the pipes to be noted and rectified before covering the pipework with the following layers.
  • Building regulations require that certain thicknesses of insulation be used when laying a floating floor. In most cases, the thickness of the grooved insulation (usually 50mm polystyrene) is enough to fully cover the heating pipes, but further insulation may be necessary, dependent upon specific building regulation requirements, to properly meet the recommended level.
  • Where additional insulation is necessary beneath the polystyrene insulation, certain compressive materials such as Rockwool or fibreglass are not recommended.
  • Each design will carry its own regulatory requirements – be sure to check these with building regulations and your underfloor insulation supplier.

 Image: commons.wikimedia.org

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