Anderson Floor Warming Underfloor Heating may be fitted using Clip Rail 16 for embedding in one or two-layer concrete and screed constructions. The rail is made of recovered plastic and manufactured so it is adaptable for length. Its design ensures full encapsulation of the pipe to maximise heat transfer.


We recommend that to achieve optimum efficiency of the underfloor heating system the use of weather dependent (weather compensation) flow temperature control, properly balanced and set in line with the design for adjustment of the primary and loop flow. We also recommend the settings are recorded for future reference.

Construction Outline

1. Insulation / Concrete floor
Insulation thickness must be designed to take account of underfloor heating needs.
2. Clip Rail 16 / 20
3. Pipe
Anderson Floor Warming Universal Pipe dia. 16mm. or Anderson Floor Warming UFH Pipe dia. 20mm.
4. Reinforcement (where required)
5. Concrete/screed
70 mm screed depth is recommended to allow proper function of the underfloor heating, i.e. in order to achieve the most even surface temperature possible (approx. 45mm required above the pipe). The minimum acceptable depth of screed is 55mm (i.e. 30mm above the pipe) where a liquid self-levelling (flow) screed is used. NOTE: increasingly “flow screed” depths are being specified less than 55mm, please ensure that full consultation is taken from the screed manufacturer and ensure that Anderson Floor Warming is aware as this may affect design.

Surface layer

Parquet, solid wood or laminated floor
Concrete surfaces are covered with a vapour barrier (DPM) and then, dependent on floor finish, with rag paper or cellfoam. The flooring should be installed in line with manufacturers instructions. Always consult Anderson Floor Warming for floor thicknesses above 34mm total and take advice from the flooring manufacturer.
Vinyl or linoleum flooring
Are laid according to the supplier’s instructions.
Ceramics or natural stone
Are laid according to the supplier’s instructions.

Drying out the concrete screed

It is extremely important that the concrete screed is sufficiently dried out before the floor covering is applied. RH measurement must be carried out in accordance with local building codes. The drying out time may be shortened by using the installed underfloor heater. The supply line temperature should in this case be kept around 5°C higher than the actual temperature of the concrete screed, though no higher than 30°C. Remember to take into consideration the curing time of the concrete or screedbefore using this method or cracks may form.

AFW Heating Circuit Manifold

The AFW Heating Circuit Manifold must be installed as shown in the design drawing. Please read the instructions enclosed with the manifold first.

Laying procedure, clip rail

Clip Rail 16 or 20 must be laid out at right angles to the loop direction. At the perimeter turn zones, the rail should be laid approx. 350mm from the wall, allowing enough room for the pipe loop. The remaining distance between the turn zones should then be fitted with further rows of rails spaced at max. 1000mm.

Laying the pipe

Lay the underfloor heating pipe out according to the layout drawing. Ensure the direction of flow in the loop is such that the supply line is closest to the outer wall. The pipe is mounted 50-100mm from the inside of the outer wall. Number and name the loops according to the drawing. The drawing probably shows various pipe distances in various spaces. An ’edge zone’ may also be necessary, e.g. if there are large window areas. It is very important to note differences in the pipe distances on installation.

Pipes should be cut using pipe shears intended for PE-X.

Expansion areas

Large areas become ”expansion areas”. An underfloor heating loop must be laid within the same expansion area without touching a neighbouring area. Only supply and return lines may cross the expansion joint, these are then protected by a protective pipe.