Underfloor Heating: Floor Construction Overview

An overview of underfloor heating and the floor types you can use.

underfloor-heating

When installing underfloor heating, it is important to consider how best to construct your floor in order to accommodate for underfloor heating system, there is a variety of flooring types from which to choose. Typically electric underfloor heating can be installed without much considering, hence its use in the retro-fit market, however, wet underfloor heating systems require careful design considerations.

Underfloor Heating floor types:

Screed Floor

Screed flooring allows for the underfloor heating system to lie comfortably within the screed itself just below the floor’s surface. The floor is constructed by lying a damp proof membrane (DPM), followed by a pouring of concrete to form the structural slab. Insulation is laid on top of the concrete, and shielded by a waterproof membrane to protect it from the screed that is to be poured on top. The underfloor heating system follows, the pipes is fixed into place by rails, staples, or a steel mesh, which is then embedded within the screed or concrete. The final finish of carpet, tiles, or stone, is laid on top.

Concrete Floor

Concrete floor is similar to a screed floor, except it is constructed by installing the insulating layer directly on top of the damp proof membrane (DPM), followed directly by the underfloor heating pipes, and a layer of screed, which forms the last layer before the finish.

Floating Floor

Floating floors are designed to sit on top of an existing floor construction. A Routed sheet of insulation, ready-set with grooves to house the underfloor heating pipes, is laid. Pipes are fitted with a series of clips which hold them in place. When fitted, the pipes, clips, and insulation layer will lie flush ready to be covered over with aluminium conducting sheet, a vapour barrier, and the final floor.

Timber Intermediate or Suspended Floor

Suspended floors are constructed with a set of timber joists between the bearing walls, supported at either end by wall plates either fitted to the wall or built into the masonry. For wider floors, one or more beams run from wall to wall carrying the joists, with the beam ends supported by the bearing wall. Large floors are supported by beams running between the supports and carrying a series of binders which in turn carry the joists. Underfloor heating pipes can be installed between joists or on top of them. One method is to fit insulation between the joists approximately 25mm below the tops of the joists. The pipework is laid on top of the insulation between joists, followed by a composition of sand and cement, followed by the subfloor and finish.

Suspended Floor with Spreader Plates

Suspended floors with spreader plates are similar to a suspended floor, but the pipes are fitted on top of the insulation, and topped with spreader plates designed to more evenly distribute heat across the floor.

Heating Pipe integrated within Floor Panel

Sometimes the process of fitting underfloor heating is simplified by replacing traditional insulation with a high value thermal quilt laid over or between joists and integrating the pipework inside a flooring panel. This saves time, reduces noise, and provides improved comfort.

Raised Access Floor System

Raised access floors of office buildings may seem incompatible with any underfloor heating system, but using spreader plates mounted between the floor tile pedestals, it is possible to fit the pipes, spreading heat to and from the tiles.

Image: commons.wikimedia.org

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