Installing Wood Flooring Over Underfloor Heating
You can read the condensed underfloor heating excerpt from our full installation guide on this page, or you can download the full installation guide below.
Because wood naturally lowers heat transfer throughout the entire floor construction, it should only be used over an Underfloor Heating (UFH) installation after consulting with a heating expert.
Please keep in mind that most Ted Todd engineered floors have a moisture content (MC) of between 8% and 10%. After a period of time under an UFH installation the MC of the wood may drop to 6%-8% or lower. This could cause some shrinkage in the floorboards.
Similarly, if the UFH system is switched off after installation (such as in the summer) the MC of the floorboards may rise again causing some width expansion. As a result, the MC of the wood floor should be carefully examined prior to installation, and if necessary, additional acclimatisation should be performed.
Similarly, if the heating system is turned off and the site’s humidity rises again, room should be made for some wood expansion.
All of our engineered floors can be used with UFH systems. Check with the UFH system’s manufacturer to ensure that the system can be appropriately controlled so that the highest temperature of the wood floor (at any point) does not exceed 27°C.
Ted Todd wood floors must be installed over UFH systems in conjunction with the Ted Todd Fidbox monitoring system, which allows the temperature and humidity of the wood floor and subfloor to be monitored and recorded.
The Ted Todd Fidbox device is vital, and an infrared heat monitor can be used to supplement it. These will allow you to adjust your heating system’s maximum operational temperature to a floor surface temperature of 27°C. This is easily accomplished in water systems by setting the flow-control valves regulator to a maximum water temperature that is compatible with the system. For electric systems, you must additionally configure the system such that the floor temperature does not exceed 27°C.
Please keep in mind that the 27°C applies to the entire floor, and hot patches can be prevalent in badly fitted systems.
The warmest spots in the floor should be used to calibrate both the water and electric systems. In order to prevent excessive temperatures in some areas, the sub-floor construction must have a heat-distributing layer that provides an even temperature across the whole surface of the floor area.
Please keep in mind that underfloor heating is intended to be a “slow” heating source. The appeal is that they emit a consistent amount of heat throughout time. The only time a temperature of 22°C cannot be obtained with a floor temperature of 27°C in most properly insulated homes is when the 22°C is requested too rapidly. In this case, using an underfloor heating system such as a standard radiator will damage the floor since the short-term temperature rise will cause the floor to overheat.
Please keep in mind that room temperature controls are not the same as floor temperature controls. To avoid overheating, the UFH heating system must have its own control system at the floor level. Colour loss in the natural tone of the floor or slight longitudinal changes in the floor are all early symptoms that the heating system is running too hot.
This is common in the vicinity of knots.
The hardwood layer in your floor will begin to shrink if corrective action is not taken promptly. The hardwood layer will curl up at the borders if this happens. In extreme cases, the dried hardwood layer will shift to the point where it is loose and begins to delaminate from the backing layer. When dried-out hardwood layers become loose, they are usually replaced; but, in some cases, the wear layer can be bonded back into place. (Using a micro nail gun to hold the boards in place while the glue cures is optional.) Replacing wear layers is a professional job that necessitates removing either the entire plank from the floor or, in certain cases, the hardwood wear layer as well. This can occasionally be done without causing damage to the floor’s finish.
The floor, on the other hand, will need to be refinished if there are no bevels between each component. The refinishing process could be simple, requiring only a moderate sanding of the existing finish and the application of extra coats of finish. In some cases, the floor will need to be sanded down to bare wood before being refinished. Please note that the adhesive bond strength of every Ted Todd engineered wood floor is tested.
The hardwood layers and core’s bonding performance fulfils all European criteria.
Underfloor heating causes shrinkage in the hardwood layer of the board, not poor adhesion, which causes wood floors to fail. Ambient humidity and temperature should be maintained at all times.
When using underfloor heating, avoid laying carpets or heavy items that trap heat on the floor, since this might cause the wood to dry up too quickly. Some electric underfloor heating systems are not suited for use with timber flooring; verify with the UFH manufacturer to ensure that the system meets the criteria.
Water Fed Systems
Before beginning laying, the UFH installer must confirm that all services running beneath the floor have been thoroughly tested and commissioned. Follow the heat up technique outlined below once the screed is dry, as stipulated in Chapter 2 – Moisture Testing. Please note that this is to ensure that the system is functioning properly and to allow the installation screed to dry out. Under no circumstances should the system be run at these high temperatures once the wood flooring is installed.
Day 1 – 20°C
Day 2 – 30°C
Day 3 – 40°C
Day 4 – 50°C (or the maximum planned operating temperature and maintained constantly for 7 days)
Day 12 – 40°C
Day 12 – 40°C
Day 13 – 30°C
Day 14 – 30°C
Day 15 – Turn off the heating system.
Allow four days before taking a final moisture reading. If there is a period of more than 7 days between the last cooling down day and the commencement of the flooring installation, the UFH system should be run at minimal operating temperature for two days. After that, the system should be turned off for at least four days before another moisture check is performed prior to laying.
Electric Underfloor Heating Systems
Some electric UFH systems are not suited for use with timber flooring; verify with the manufacturer to ensure that the system will follow the general criteria. If the system is suitable, proceed to ‘Floating Installation’ section for instructions.
Underfloor Heating Systems Over Suspended Floors
If the UFH is suspended in joists or an overlay system is used, be sure the heating system is rated for use with engineered wood floors and follow the manufacturer’s installation recommendations. Always check joist spacing as per Chapter 4 of our installation guide and follow our basic UFH rules.
Underfloor heating one part of a continual floor area
If the UFH is to be installed in only a portion of a continuous floor area (for example, in an open lounge-diner area with UFH only in the lounge area), the floor area must be divided. There must be a separation between the heated and non-heated areas. This is when a Ted Todd “T” section comes in handy. This is to prevent any issues with differential expansion or shrinkage.
Reaction To Fire
When laid without an air gap underneath, all Ted Todd wood floors with a thickness of 8mm or more can be classified as Dfl-S1 at the very least, according to BS EN 14342-2013. When built with or without an air gap underneath, most Ted Todd 20mm thickness 2-ply Oak flooring can be categorised as Cfl-S1 according to BS EN 14342-2013. On request, specification sheets for each Ted Todd floor, including the fire classification, are available. Please review the design specifications for the project where the wood floor will be installed to confirm that the wood floor and installation method meet the requirements.