Underfloor heating under your parquet

Which type of underfloor heating do I choose?

When choosing your underfloor heating, you generally have two options: electric underfloor heating and a hot water system. The hot-water system can be divided into a wet and a dry circuit.

Electric underfloor heating

An electric system can be installed almost directly under the parquet. The system runs mainly on thin heating wires or foil mats. In terms of energy consumption, it is equivalent to a hot water system but, as with all other heating appliances, you do need to use it sustainably. You will pay a little more for an electric system than for a gas one, but it is safer. Moreover, it is often used as a supplementary heating system, in combination with a radiator for instance.

Hot water systems

The hot water systems differ in the way the water pipes are installed in the screed. The hot water pipes of a wet system are in cement. The cement will therefore provide insulation. This will slow down the rate at which your house heats up or cools down and consequently your energy consumption will increase.

A dry circuit consists of several components: an insulating underlay, galvanised metal or aluminium channels with heating pipes and a cover layer. These channels ensure good heat conduction and function much faster than a wet hot water system. It goes without saying that both hot water systems work through the central heating system.

We recommend working with an electric system or a dry hot water system. Be sure to discuss the choice for parquet and underfloor heating with your heating specialist. He will make sure that the limitation of your heating is perfectly adjusted.

The humidity in the room

Wood is a hygroscopic or water-attracting material and is therefore very sensitive to humidity. It is therefore important to ensure that the ratio between the effective and maximum presence of water vapour, or relative humidity, in your room is correct. Ideally, these percentages fluctuate between 40-55%, with 30-60% as limit values.

In order to guarantee these percentages, it is best to ensure that there are (temporary) heating and a ventilation system in the room where you want to install your parquet. This way, you create a favourable indoor climate in your home. For more technical information on this subject, please visit the website of the Belgian Building Research Institute (BBRI).

What type of wood do I use?

Wood is a 'living' material. This means that it can deform, spring, warp or even crack. It is therefore essential that you choose a stable and dried wood species to lay your parquet. Some suggestions from our experts:

• Afrormosia
• Afzelia
• Merbau
• Teak
• Wengé

These types of wood are considered very stable and less sensitive to changes in humidity than, say, beech or ash.

Also choose planks with the right width. The golden rule here is that the planks should have a maximum width of 140 mm or 14 cm. This way you will create enough joints and the planks will have enough room to move.

Solid parquet

With solid parquet, it is also important that you use an underlay to attach your planks to. You should then glue the planks to the sub-parquet. Floating parquet is not recommended in most cases because it forms an air-insulating layer and the heat will not penetrate the floor as easily.

Another option for laying your parquet safely is by using multi-layer parquet. The parquet is made up of several layers and is less likely to deform. After all, it has more room to manoeuvre due to its multi-layer character.

How do I create the right subfloor?

When laying your parquet, you must also take the subfloor into account. It is best to ensure that there are sufficient expansion joints and that your screed is poured in correctly. Ideally, the heating pipes should be laid in a cement-bound or anhydrite screed and this layer should be at least 30 mm thick. To let your screed dry, count one week per centimetre. From 5 cm thickness, it is best to take 2 weeks. The moisture of your cement-bound screed is maximum 1.8% CM (absolute moisture percentage based on a carburetion measurement). With anhydrite this is even a maximum of 0.3% CM.

For example: if you lay 8 cm of screed, you will have to wait 5 weeks for the first 5 cm and 6 weeks for the bottom 3 cm of screed. So 11 weeks total drying time.

When your screed has dried out sufficiently, the floor heating can be started up. The best way to do this is to use the following schedule:

1. Ventilate your room properly.
2. Warm up the water temperature until you reach 20°C. From then on, increase the temperature by 5°C every 24 hours. Until you reach a water temperature of 45°C. The surface temperature will then be approximately 27°C. Keep this temperature for as many days as the thickness of your screed. In our case, 8 days.
3. Now lower the temperature again by 5°C per 24 hours until you reach 20°C again.
4. Repeat this process once.

48 Hours before installation, switch off the underfloor heating. Lay your planks in a closed pack in the room where you will be installing them. Make sure that each package lies on the floor individually so that the planks can acclimatise. Do not place them at an angle against the wall; this could cause the boards to warp. The temperature in the room should not be lower than 10°C and higher than 20°C. The relative humidity should be between 45%-60%. 

The underfloor heating can only be switched back on 3 days after installation. Again, follow the same steps as in the diagram. The water temperature may not exceed 45°C while the surface temperature may not exceed 27°C. The humidity must also remain within the limits (45-60%) in order to avoid shrinkage or expansion.

How do I install my parquet?

Make sure that your basic floor (= dried screed) is ready to use. In other words: your screed must be a clean, even and dry surface. Check whether or not it is necessary to lay an underlay on top of your screed. This can be useful for soundproofing, damp-proofing or levelling the floor. If you would like more information about this, you can contact us at info@nobletimber.eu.

Now you can really get started. It is best to start in a corner where you walk into your room and lay your first plank with the groove towards the wall. Use spacers around your parquet and give the wood the necessary space to work. It is sufficient if these blocks are about as thick as the thickness of your plank.

Then apply some glue to the end of the next plank and slide the parts together. Using a hammer and a rubber or wooden block, tap the boards together. Complete your first line in this way.

Start the next line with the sawn remainder of your last plank (if this is larger than 50 cm). Apply glue again in the groove of the long side and on the head side of the board. Then hold your board at an angle of about 30° and let the tongue click into the groove of the board above. Tap it again with your hammer and the block. Any residual glue on the surface should be wiped off with a damp cloth. 

If there are any obstacles, cut out the shape of these with a jigsaw. Enlarge the cut-out by 10 mm on the outer edges. In this way you will be able to absorb the expansion of your parquet. You can then use a rosette to cover the holes.

The last row will probably have to be sawn to make your parquet fit in the room. Always draw this on your planks to saw them correctly and to size. Again, take into account some extra space for the expansion of your planks.

Completion

The simplest part of the installation process. You remove your spacers, apply your skirting boards and give your parquet another layer of maintenance oil. Let your parquet dry for a while and you are ready.