Frequently Asked Questions (FAQ)

On this page you will find a number of frequently asked questions about the JK fermafloor system. Hopefully you will find the answer to your particular question. If not, feel free to contact us.

Choosing floorheating instead of traditional heating has a number of advantages. For one it increases the comfort of living, lowers the energy bill and gives complete freedom in decorating the rooms, because there are no longer any radiators in the way. Choosing specifically for the JK fermafloor system offers additional advantages like higher fire-resistance, sustainable materials and an improved sound-insulation.

To find out whether the underfloor construction meets the required standards, a structural engineer will need to be hired to research the underfloor. The stability of the underfloor needs to be in good condition; this is a deciding factor in determining whether the floor needs to be partially or completely replaced and/or altered. For more information on the required standards see step 01 from option A or option B on the JK fermafloor page.

Who can be consulted for a quotation completely depends on the phase the project is in. When a preliminary design still needs to be made, one of the advisors from fermacell or JK floorheating can provide you with advice and a price formation. If the project is already in the execution phase, the technical execution can be done by one of the selected fermacell Experts. If desired, it is possible to also include one of Uzin Utz Netherlands’ specialists for tailor-made advice with regard to the correct floor finish.

All JK fermafloor system elements have been tested and guarantee the best quality. Fermacell’s Flooring Elements have a European Technical Approval by Kiwa, which means that the flooring elements have been thoroughly tested and approved. The JK flextube Inverse Soft floorheating pipes by JK floorheating have also been tested and approved with certificates by Kiwa. Besides that, the JK sealing compound, JK fermafloor primer and JK fermafloor levelling compound, combined with the right finishes adviced by Uzin Utz Netherlands, offer an extra guarantee with the Uzin Utz Warranty System. This Warranty System offers a 10 years certainty. Uzin Utz Netherlands draws up an agreement with you tailored to the project in question. Free of charge. For this one of the 25 experienced Technical Commercial Advisors is linked to the project for a tailor-made advice with an extensive assessment.


The build-up height is dependent on the chosen option and the eventual floor finish. It is possible to calculate the build-up height without floor finish for both options. There is also a difference depending on the chosen flooring element (with or without 9 [mm] felt layer). When the 2E22 flooring element is chosen there is no 9 [mm] felt layer. The 2E26 flooring element does have this, which is why this gypsum fibreboard is higher.

Option A with 2E22: 25 [mm] gypsum fibreboard + (at least) 5 [mm] smoothing compound = 30 [mm]
Option A with 2E26: 25 [mm] gypsum fibreboard + 9 [mm] felt layer + (at least) 5 [mm] smoothing compound = 39 [mm]

Option B with 2E22: 25 [mm] gypsum fibreboard + 10 [mm] top board = 35 [mm]
Option B with 2E26: 25 [mm] gypsum fibreboard + 9[mm] felt layer + 10 [mm] top board = 44 [mm]


The JK fermafloor system is an accepted system, based on research and years of experience, with two tested and released options for fixing the floorheating pipes. Of course you are free to choose a different way of fixing the floorheating pipes. Yet, only when one of the two tested options by JK fermafloor are chosen it is possible to give out a warranty on the system.

In order to give warranty on the JK fermafloor system the floor needs to be finished according to one of the tested options. This means that when option A is chosen, a layer of primer and smoothing compound are always needed, as adviced by Uzin Utz Netherlands, to give of warranty on the system. With option B the need to use a smoothing compound on top of the top board is dependent on advice from fermacell.

To answer this question a heat release calculation needs to be made. This calculation is based on the recorded data from the design. Of course all this is dependent on the residents’ way of living.

In order to begin using the floorheating system, a heat-up procedure needs to be followed after the floor finish has been placed on top of the gypsum fibreboards and the ground floorheating. Naturally, how long it takes to start heating up depends on the chosen type of floor finish. When the floor finish has dried/hardened enough, according to the procedure the water flow regulator of the manifold can be turned up to 20 [°C]. After this the temperature needs to be raised by 5 [°C] every day, up until 40 [°C]. This basically means that after 12 days the floorheating should be up to the correct temperature and can be used. Yet, if the temperature in the room is still too low, it is possible to raise the temperature of the water flow regulator to a maximum of 50 [°C].

A more elaborate explanation can be found in JK floorheating’s user manual.

Naturally, each project is unique. Generally, when calculating with one crew of two mechanics, during a normal workday it is possible to screed, lay and seal 100 [m²] of floorheating. A 16-hour drying time of the JK sealing compound needs to be added when choosing option A. It is also important that the room temperature is between 15 and 30 [C°].

In the Experience Center (at JK headquarters) in Ede (NL) all forms of floor finishes, with both tested systems, can be seen and felt.

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