Most wood-engineered products are highly suitable to be installed on Underfloor Heating systems, such as Wood You Like's Basic 15/4 and the load-breading (20/6) range. The cross-layered (plywood) backing gives it more stability and is not very prone to shrink as much as solid boards can when installed almost directly onto a heat source.
We do recommend you check if the product you buy is suitable and to follow the recommendation of the manufacturer on preparation/installation instructions.
However, to obtain the best performance of your floor in the long term, it is important to follow these guidelines. As there is no reliable way of recording or monitoring the heating-systems settings and room conditions over time, it would be impossible to prove or disprove or whether all the guidelines had been followed. Therefore we can not give a guarantee.
In practice, any floor is almost certain to shrink when used with an underfloor heating system, and there will be some movement of the floor. This is due to the relatively high moisture content. After a month’s use with an under-floor heating system the levels of the moisture in the wood drops. This loss of moisture manifests itself as shrinkage. If the moisture loss is severe, there can also be a breakdown in the cellular structure of the wood, leading to splits in the wear-layer. (this can happen with Jatoba, Maple for example).
Some species are more suitable for use with an under-floor heating system than others. The following species have been tested and proven to be stable: European Oak, Merbau, Walnut and Iroko. We don’t recommend other species to be installed on an under-floor heating system.
Steps to take
If you install a wood-engineered floor on a under floor heated sub floor, there are some conditions you should respect:
- Tubes should be located minimal 3cm below the surface of the screed.
- The screed must dry naturally to below 1,8% moisture content (anhydrite: 0,3%). Do not turn the under-floor heating on before the correct moisture level is achieved
- The maximum temperature of the surface of the screed should be 28 ° C and steady.
- Relative atmospheric humidity should be maintained between 50-65%, adjust by ventilate or using a humidifier.
- Make sure the boards can acclimatise in the area for 3 to 7 days before installation. Keep air temperature between 10° C and 20° C and relative atmospheric humidity between 50-65%.
- Leave the board in the shrink-wrapped foil until the installation.
- The use of standard, micro bevelled planks will minimise the visual impact of shrinkage. A square edge board will show up the shrinkage much more through slight gapping.
- Heath up the water of the system to 20° C
- Raise the temperature every day with 5° C until a maximum of 45° C
- Maintain this temperature for 5 days.
- In the following days, lower the temperature with 5° C every day until you reached the temperature of 20° C again.
- Than turn off the system.
Installation of the wood-engineered floor:
- A PU-based adhesive, such as Sika T54, Mapei P990 or similar, should be used, and will act as both adhesive and moisture barrier, and thermal conductor.
- Wood should be sealed as soon as possible after laying. Oiled floors should be fed and maintained more often than conventional, non under-floor heated floors.
After installation of the wood-engineered floor:
- After fitting, the floor should be allowed to cure for 2 days before the heating is turned on.
- The heating should initially be turned on at the ambient temperature.
- It should then be raised by no more than 1° C per day until the required temperature is reached.
- The room temperature should be maintained between 20°-23° C
- The heating system should be run in strict accordance with the manufactors’ instructions.
- Beware of leaving solid furniture and/or heavy rugs in one position for any length of time. If the floor is “capped” in this way - trapping heath - this will lead to cupping and gapping, from which the floor may not be able to recover
Two years after this floor was installed the owner noticed the rug (underneath a table) was lifting. Removing the rug he did not discover a hidden toy what he first thought was causing the 'bump' but the delaminating of one of the boards.
The extra insulation of the rug allowed a build up of heat which then softened the adhesive between toplayer and backing to allow the tensions in the Oak to pull it apart.
Underfloor heating and wooden flooring is fine, adding a rug isn't!
Parquet floors - the most stable choice
An original parquet floor, installed the "Dutch way" will give your client the most stable floor possible and is in fact one of the few Solid floors that can be used safely in combination with UFH.
As you can see on the image: every 10mm wood block connects with at least 3 blocks of 7-finger mosaic (Industrial Grade - 8mm thick). In other words, the floor is "engineered" at your clients home.
If instead of screed/concrete the UFH system is covered with WBP plywood, this then replaces the Industrial Grade mosaic subfloor. The wood blocks - in any pattern your client likes - is then glued straight onto the plywood.
Example of Oak Prime - large double plait pattern - installed over UFH (with plywood subfloor).