“Is your flooring compatible with underfloor heating” is one of the most common questions we get asked at Kite. And almost always, the answer is “yes”. Most engineered wood floors are compatible with some form of underfloor heating, but the tricky thing is that not all floors are compatible with every system. So the correct question should be,
“Is the floor I want, compatible with the system I want?”
And the answer to that question is not always “yes”.
At Kite, we talk a lot about fitting strategy (there’s more than one way to fit a floor…), but with heating systems, it’s even more important to plan things out from the beginning. Our nightmare scenario is when a customer orders a non-refundable, bespoke floor, and then we discover it’s not compatible with the underfloor heating system they have fitted. Oh dear. So, how do we avoid this?
1. Is the system water-based or electric?
Broadly speaking, there are two types of underfloor heating systems, one with pipes (water-based), and one with wires (electric). We won’t go into which is better, but whichever system you go for, you must, must check your fitting strategy works.
Water-based systems, that are set in a screed, are almost always compatible with wood floors. However, electric systems, that aren’t part of the structure of the building, are commonly designed for floating floors (planks that are not fully bonded to the subfloor). This works fine with plank flooring, but parquet, such as Herringbone or Chevron, has to be glued down.
There several electric systems that are foil-based, and you simply cannot glue floors to them. An example of an electric, foiled-based system would be this from Warm Up – Heating Matt Range. This means they are not compatible with parquet. There are electric systems that are compatible with glue-down floors; these are often the ones used with tiles – Sticky Matt. Always, always, check with the technical teams at your underfloor heating company, as to whether your floor can safely be fitted, before ordering the system.
2. Is the system within the subfloor floor or on top (an overfloor system)?
If the system is within a screed, it will be more structurally sound than if it sits on top. Remember, for us to safely fit a floor, the subfloor should be level (less than 3mm deviation across a 2m rule), and sound (so no movement). Regularly we come across water-based systems that sit on top of the subfloor, such as Wundertherm. These are cheaper and easier to install than structural systems. However, often these have been loosely fitted onto chipboard, so there is movement and creaks.
If you have chosen a plank floor, fitted floated, then normally it can be made to work, although there may be floor bounce, if the system isn’t flat. But glued-down parquet is much harder.
The manufacturer recommendation is to apply a quick drying levelling compound across the system, and then glue to this, but if there is movement in the subfloor, cracks appear. And even if no cracks appear, it’s expensive, as the compound has to be 1) flexible to heat changes, so a premium product, and 2) deep to avoid cracking. You may think you’re ending up saving money, but when we send you the levelling bill, you’ll think again. At Kite, we’ve tried other solutions, but fundamentally, if the subfloor isn’t structurally sound, you shouldn’t be fitting a glued down product.
And again, this is not ideal, if the customer has bought a bespoke glued-down floor, and the system has already been fitted!!
As a business, we’re now trying to avoid fitting parquet to these types of systems, and are strongly recommending plank floors, fitted floated. But we also know sometimes clients have their heart set on parquet, and the systems have already been fitted!
3. A single heat source
As we’ve explained before, wood is a natural product, and when it dries out it shrinks, and when it picks up moisture, it expands. This means, if you’re using an underfloor heating system, it must be under the entire wood flooring area, not partially underneath, as one area will expand and contract more than the other.
The solution to this is to put a break in the floor, covered with a door bar, but that doesn’t look good. So when designing your system, make sure you think this through.
4. Before, after and during fitting…
Before floor fitting, for most water-based systems, a commissioning process must take place, whereby the systems is gradually turned up, and then down. The guidance from the British Standards is as follows, but every system may be slightly different;
12.6.4 Precautions prior to laying where underfloor heating is to be use 
This process almost always takes our customers completely by surprise (it is bizarre, that the companies that actually fit these systems never seem to mention it to their customers… but hey, we’re just flooring guys :).
The reason for this is you cannot fit a wood floor on a heating system, and then simply crank it up to the max, because then the timber reacts to that shock. This process also helps with the drying of the screed, another one of our fitting challenges (read our Blog on this). A couple of days before the fitting starts, the system must be turned off, then turned up gradually after the floor is fitted.
5. Speak to the technical teams
Almost all underfloor heating manufacturers have technical teams that are super helpful. Before ordering your system, give them a call, and check through everything, from the type of materials, fitting strategy, and also how to commission your system. The worst that can happen is you’ll find out you’re on the right track, or they could easily highlight something your contractor, architect or project manager missed.
We’ve had several situations where we’ve arrived to fit a floor, and something is wrong with the underfloor heating. This then sets off a rubbish chain of events involving blame pointing and ultimately costs.
At Kite, we try our best to give great advice, but we’re not the project manager for your build. So, make sure, whoever is, checks your final strategy.
So there you have it, five things to think about with underfloor heating systems and wood floors.
Whether you buy through us or anyone else, remember, the most important question is not, “is my flooring compatible with underfloor heating”, it’s….
“Is the floor I want, compatible with the system I want?”.
Happy Project Planning.
