Engineered Oak Flooring over Underfloor Heating
Marchand 20mm engineered oak is suitable for underfloor heating, hydronic and low-temperature electric, when the system is set in screed and run within the limits on this page. Plenty of engineered floors claim the same; the difference is usually the wear layer. A 6mm oak face on a cross-bonded eucalyptus core moves less than a thin veneer on a softwood ply, and it has been proven over heated slabs in Central Otago winters. This page is our full declaration; the signed document is at the bottom.
The one number that matters
The surface of the floor must never exceed 27°C. Not the water temperature, not the screed, the surface the boards sit on. A thermostat with a floor sensor is the way to hold it there, and the warranty also sets limits of 75 W/m² thermal flux and 0.15 m²K/W thermal resistance. Above 27°C oak dries, shrinks and checks, and no warranty covers that.
Which systems
Hydronic. Warm-water pipes set in the slab or a screed. This is the system most Marchand floors sit on and the one we would choose; the heat is even and the water temperature is easy to limit.
Electric. Low-temperature electric cable or mat systems, fully embedded in a levelling screed so heat spreads evenly before it reaches the boards. Electric systems laid directly under the adhesive, or foil systems designed for floating floors, are not approved.
Any system must be fully embedded, controlled by a thermostat with a floor sensor, and commissioned before the flooring goes down.
Before installation
Run the heating for two weeks. The system should have been operating for at least two weeks before the boards are installed, to drive residual moisture out of the slab or screed and to prove the controls. Then turn it down to a moderate setting for the installation itself.
Test the slab. Slab moisture at or below 5% by weight, or 65% relative humidity, measured with the heating off for a period beforehand, and a primer applied as the installation guide describes.
Acclimatise the boards for 48 to 72 hours in the heated room, in closed packs, with the room held between 40% and 60% relative humidity. Boards leave our warehouse at 6% to 9% moisture content and need time to meet the room.
Installation
Full glue-down with a flexible wood flooring adhesive, exactly as for an unheated floor. A floating installation over underfloor heating is not approved: an air gap under the boards insulates them from the heat and lets them move. Glue-down keeps the oak in contact with the screed, which is what makes the heating work and the floor stay flat.
Bringing the heat up
After installation, leave the heating at its moderate setting for the adhesive to cure, then raise the temperature gradually over at least three days to the running level. Do the same in reverse at the end of the season. Sudden changes, up or down, are what stress a timber floor; a slow ramp is what keeps it settled.
Living with it
Keep the room between 40% and 60% relative humidity. Heated floors in dry alpine winters can drop below this, and a humidifier makes the difference. Rugs on a heated floor trap heat beneath them; use thin, breathable rugs and avoid rubber backings. Follow the after care guide in every other respect.
Proof
A Marchand floor installed in 2021 over an older heated concrete slab, more than 200m² of it, has been monitored since. There has been no warping, delamination or cupping, and no change in performance, which is what a 6mm wear layer on a stable core should deliver.
Frequently asked questions
Can engineered oak flooring go over underfloor heating in New Zealand?
Yes. Marchand 20mm engineered oak is approved for hydronic and low-temperature electric systems set in screed, with the floor surface held at or below 27°C.
What is the maximum floor temperature?
27°C at the surface, controlled by a thermostat with a floor sensor. The warranty also limits thermal flux to 75 W/m² and thermal resistance to 0.15 m²K/W.
Can it be floated over underfloor heating?
No. It must be fully glued down so the boards stay in contact with the screed.
How long should the heating run before installation?
At least two weeks, then turned to a moderate setting during installation and raised gradually over three days afterwards.
Which is better, hydronic or electric?
Both are approved when embedded in screed. Hydronic gives the most even heat and is easiest to limit; electric must be in a levelling screed, not laid directly under the adhesive.
Does underfloor heating affect the warranty?
Not when the system is approved and run within the limits. Exceeding 27°C at the surface, or using an unapproved system, voids it.
The declaration
Download the Underfloor Heating Declaration (PDF)
Related
Last reviewed September 2026.