Anderson Floor Warming Underfloor Heating using XPS is suitable for floating floors on solid floor constructions. The system includes a type-approved insulation board in XPS. This material has high insulating properties as well as being excellent for short or long-term loads. It also has good acoustic suppression characteristics. Slotted and turning boards are available in 30 and 50mm thicknesses.


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.

The boards must only be laid on load bearing floors, such as screed, concrete or beam & block. If using chip/ply floorboards, battens or joists must not exceed 600mm c/c. Do not lay over other insulation, as multi-layers of insulation causes poor floor resilience (excessive spring).

Construction Outline

1. Solid floor construction
2. AFW Slotted Board XPS
Dim. 1200 x 600 x (30 or 50)mm, with 3 slots c/c 200 mm suitable for use with AFW Heat Distribution Plate 16 and AFW Universal Pipe 16mm.
3. AFW Heat Distribution Plate 16
4. Pipe
Anderson Floor Warming Universal Pipe dia. 16mm.
5. AFW Turning Board XPS
Dim. 1200 x 300 x (30 or 50)mm
6. Vapour barrier and cell foam/rag board

Surface layer

Parquet, solid wood or laminated floor
For floating applications, concrete surfaces are covered with a vapour barrier (DPM) and then, dependent on floor finish, with rag paper or cell foam. Note that rag board must never be laid directly on the underfloor installation as this may cause squeaking. Rigid flooring is laid across the underfloor heating circuits. For fixing of some solid wood floors it may be necessary to lay 12mm plywood above cell foam. Floating engineered (laminated) floors generally do not require an intermediate plywood layer. The flooring should be installed in line with manufacturers instructions. Always consult the flooring manufacturer. Always consult Anderson Floor Warming for floor thicknesses above 34 mm total and take advice from the flooring manufacturer.

Vinyl or linoleum flooring an carpet
Dry areas
Deitermann Plastocol F1 or Ardex S48. Take care to ensure that the top layer of plasterboard over-laps the joints of the layer below.

Tiles require an intermediate floor, over the underfloor heating, of 2 layers of 13mm floor grade plaster board which are glued together with Kiilto Flytfix mixed with Kiilto Fixbinder. Apply the glue with a “putty knife”, and then comb it out using a notched trowel (6-8 mm). Mount the plaster board within 10-15. The board joints much not be placed next to one another. Lay the carpet after the glue has dried, approx. 5 hours.

Wet areas and as an alternative solution for dry areas
For wet rooms, and an alternative solution for dry rooms, screed (including self-levelling) can be laid over the under floor heating. Lay 2 layers of good quality DPM over the under floor heating and ensure the DPM forms a skirt up walls of at least 65mm. Tape seal all joints. Lay the screed minimum 45mm deep. Wet areas require waterproofing applied as the manufacturers directions.

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, boards and heat distribution plate

1. Turning Board
Lay out the turning boards where the pipe is to be turned according to the drawing. After laying the pipe, gauge blocks must be cut from the accompanying filling strip in order to fill the empty space in the turning compartment. To allow for movement, leave 5mm clearance by walls, pipes and door frames.

2. Slotted Board
Then lay out the slotted boards between the turning boards. To allow for movement, leave 5mm clearance by walls, pipes and door frames.

3. Heat Distribution Plate 16
The Heat Distribution Plate is to be laid edge to edge with the slotted board in the turning compartment. The plate must cover joints between two slotted boards. To make the necessary adjustments, the plates may be laid out later with a relative distance of 10 – 100mm and then pressed down into the board slot. The plate may be adjusted lengthways at its bending groove. The slots in the slotted board must be carefully cleaned before the plates are laid out.

Laying the pipe

Arrange the piping to avoid hindering accessibility of the supply and return lines.

Loose lay the pipe out according to the layout diagram. Ensure the direction of flow in the loop is such that the supply line is closest to the outer wall. Number and name the loops according to the drawing. Check before you lay the pipe that the slots are clean.

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

When many under floor heating circuits will be connected to the manifold, there is a risk that the load bearing of the upper floor will be inferior. In such cases, it is appropriate to remove part of the slotted board by the manifold and fill out the space with grout.

4. Piping over turning boards
It is occasionally necessary to take make an additional route to accommodate the return flow over the turning board. In this case, lay a piece of DPM (0.2mm) under the pipe and a piece up on the turning board so that pipe and insulation do not rub against each other. Anywhere, where there is a risk of friction between the XPS insulation and the pipe, isolate with DPM; this will prevent sqeaks and other noises.

5. Turn the pipe as shown in the sketch.
Press or tread down the pipe into the slot of the plate. After assembly the pipe must lie in the slot and must never under any circumstances touch the overlying surface layer.