Underfloor Heating Supply offers a low profile dry screed board system.


RETRO18 is an ultra-low profile British engineered board which is the same height as a 5p coin (18mm).The Fermacell gypsum fibre boards are engineered gypsum flooring panels with a 60% recycled content, which gives a strong and quickly-installed dry screed system.


Retro Fit

The boards are pre-grooved and pipes are laid directly into the channels. The boards have a high thermal conductivity (0.38W/mK) so heating response times are quicker and energy use is reduced without the need for additional elements to act as the heat emitter. The boards are butt-jointed and can be screwed and glued to the sub-floor ensuring a solid floor finish.


The channels accept 12mm pipe at 150mm centres giving a low profile system.


This allows you to lay underfloor heating on top of your existing flooring, without significantly raising the floor level.

The system is very different to traditional methods that use a cementations screed poured around and on top of the piping; which can raise the floor level by at least 50mm! Most suppliers of this type of retro-fitted system offer a combination of straight connection boards and an end board for the returns. However, this type of layout can be both more expensive and more problematic to install as it requires two different elements, rather than one single board.


In Contrast, the unique layout of the grooving on the boards from Underfloor Heating Supply mean that only one board is required to provide both the straight and return parts of the installation. This serves to both reduce purchase cost and simplify installation.


Features and Benefits


  • Installed over any floor - The Retrofit system can be installed over any existing concrete or wooden floor.
  • Versatile - An ideal partner for all heat sources, including boilers, heatpumps and biomass. It will also work alongside an existing radiator system and integrate into most heating systems.
  • Installed in any room - Suitable for installation in any room type, including conservatories.
  • Installed on any level - The system can be installed on ground and upper floors of buildings.
  • Installed with any floor type - Any floor can be laid over the system, including carpet, vinyl and linoleum.
  • Floating floors - Laminates, real wood and engineered floors can be fitted as a "floating floor" directly over the panel.
  • Replaces radiators - There is no need for supplementary heating.
  • No need to excavate the floor - The Retro18 system provides a solution for projects where the excavation of the floor is too expensive or intrusive.
  • Height of a 5p coin - The system has an 18mm depth before the floor coverings are fitted, around the same height as a 5p coin.
  • Rapid heat up – As the Fermacell board is a ‘dry screed’ providing thermal mass, the boards transmit heat efficiently resulting in a floor that heats up a much quicker.
  • Directly tiled over - The dense, rigid, thermal gypsum board can be tiled over directly with just a thin de-coupling layer (mesh) in-between.
  • High thermal output - Up to 125W/m2.

Underfloor Heating Supply are now stocking retrofit products. The RETRO18 range of overlay board allows you to lay underfloor heating over old flooring without having to spend a significant amount of money and time excavating the floor. The best part of the RETRO18 range of overlay boards is their height – at just 18mm, or the height of a 5p coin

The RETRO18 Fermacell gypsum fibre boards are a homogenous composition of gypsum and cellulose fibres, recycled from waste paper and water.

One of the main issues with installing wet underfloor systems in an existing property where the floor structure is already in place, is often the potential upheaval of the floor. The system’s profile is too high to be laid over existing flooring, often increasing floor height by at least 50mm plus a thickness of insulation. Care must be taken to consider the quality of an insulation layer which is often ignored by other suppliers – insulation beneath underfloor heating is vital to ensure correct control and keep running cost to a minimum. Underfloor Heating Supply recommends the use of SuperfoilUF insulation beneath their Retro18 dry board system.