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Best Flooring for Radiant Heating: Tile, Stone, Engineered Hardwood, Vinyl Plank, Laminate and Carpet Ranked by Heat Transfer and Risk
Flooring & Tile
The Best Flooring for Radiant Heat, Ranked by How Much Heat Gets Through It and How Much Can Go Wrong Under It
A heated floor is a big, slow, gentle heater, and the flooring is the last thing between it and your feet. Some floors let the heat straight through and do not care how warm they get. Some let most of it through but have a temperature they must never pass. One of them is a blanket, and you would not put a blanket over a radiator and expect a warm room. I have been putting floors over heated concrete since the early 1990s, in my own houses and my clients’, and this is the order I would rank them in, with the reason for each and the Simcoe County price to put it over a slab.
The ranking
| Rank | Floor | R-value of the covering | Sheet cap | What goes wrong | Installed over a slab |
|---|---|---|---|---|---|
| 1 | Porcelain or ceramic tile | about 0.2 | None that matters | Cracks if the slab cracks under it; use an uncoupling membrane | $15.75, $19.25 with membrane |
| 2 | Natural stone | about 0.1 to 0.2 | None that matters | Price, and soft stones stain; heat is not the problem | $25.25 at mid grade |
| 3 | Engineered hardwood, glued down | about 0.5 to 0.7 | 27 to 29 C | Gaps and checking if the surface runs hot or the house runs dry | $12.75 |
| 4 | Vinyl plank (SPC), glued down | about 0.2 to 0.3 | 27 C, some 29 C | Expansion, and dark planks in a south window | $7.00 |
| 5 | Vinyl plank, floating | about 0.3 to 0.5 with pad | 27 to 29 C | Gaps at the ends of long runs; the pad costs you heat | $6.00 |
| 6 | Engineered hardwood, floating | about 0.9 to 1.1 with pad | 27 to 29 C | Hollow feel, and the pad is insulation | $9.25 |
| 7 | Laminate with underlay | about 1.0 | 27 C, a few 29 | Peaking and swelling if anything spills; the underlay is insulation | $5.50 |
| 8 | Carpet and pad | 1.5 to 4.0 | Not an issue | The floor is warm and the room is cold; the slab has to run hotter to push heat through | $5.00 |
R-values are typical of the products, not a spec; the manufacturer’s sheet gives the real one. Prices come from the flooring price table in this section, with glue-down labour over a slab where the floor is glued.
The two numbers that run the whole page
On the slabs we build the water goes into the tubing at about 40 C and the floor surface runs 30 to 37 C, which is what makes a heated floor pleasant, and what has been under our tile, vinyl and engineered hardwood for thirty years. Under tile nobody cares. Under wood, laminate or vinyl the manufacturer’s sheet caps the surface at 27 to 29 C and the warranty hangs on that number. Run warmer and you are trusting the builder’s experience and the product, not the warranty. If the sheet gives no number at all, the product has not been tested over radiant and you are the test.
The radiant compatibility article goes through the temperature rule in detail, and what it means for a system that was designed hot. A boiler set to 60 C to push heat through carpet will cook a wood floor the day the carpet comes out. The flooring and the heating design have to be decided together, which is why we size our systems from a real heat loss before anyone picks a plank.
Why tile and stone win without trying
Tile is a thin sheet of fired clay with almost no insulating value, and it does not shrink, swell, cup or off-gas when it gets warm. Put it directly over the slab and the floor surface tracks the slab temperature within a degree. Nothing else does that. It is also the only floor on this list where the surface temperature limit is somebody else’s problem: a tile floor at 30 C is uncomfortably warm to stand on, but the tile does not care.
The one thing that does go wrong is the slab itself. Concrete cracks, heated concrete moves a little with every cycle, and tile bonded straight to it cracks where the slab does. An uncoupling membrane between the two is $3.50 a square foot and I would not tile a heated slab without one. Stone is the same story with a bigger invoice. Tile over a heated slab is a tile question more than a radiant one.
Wood and vinyl: the floors with a number on the sheet
Engineered hardwood is the floor most of our clients want over a heated slab and it works, with conditions. Glue it down, so there is no air gap and no foam pad between the heat and the wood. Keep the planks under about 5 in. wide and the house between 35 and 55% relative humidity. Know the surface temperature, with a floor sensor or a mixing valve, and decide whether you live by the sheet’s 27 to 29 C or by thirty years of experience. Do those four things and a good engineered floor over a heated slab behaves better than a solid floor over a cold crawlspace, because the temperature in the slab barely changes from October to April. The engineered over radiant page has the species, widths and start-up procedure.
Vinyl plank is cheaper and thinner and most rigid-core products are rated for radiant. The sheet cap is the same 27 C, 29 on a few, and the thing that actually bites is expansion: a 40-ft run of floating SPC grows and shrinks with floor temperature, and the gap at the wall has to allow for it. Glue-down LVP sidesteps most of that and transfers heat better. The vinyl over radiant page covers product limits and the dark-plank-in-sunlight problem, which is a real one.
Laminate and carpet: where the heat stops
Laminate is a fibreboard core with a picture of wood on top, and every manufacturer insists on a foam underlay under it. The core is about R 0.6 and the underlay another R 0.4, so you are at R 1 before the furniture goes in. It will work over a heated slab in a well-insulated house, and its sheet says 27 C like the rest, but you are paying for heat you are not getting, and a spilled dog bowl does what spilled dog bowls do to laminate.
Carpet and pad is the blanket. A medium carpet over a 1/2 in. rebond pad is R 2 to R 3, and a thick one with a felt pad passes R 4. The slab under it still works; it just has to run hotter to push the same heat through, which costs fuel and makes the floor under the carpet warm and the room above it not very. If a basement bedroom must have carpet, a thin carpet over a thin, dense, radiant-rated pad is the compromise, and the heating designer needs to know before the water temperature is set. The R-value page puts numbers to all of this.
Rules of thumb
- Pick the floor before the heating design is finished. The water temperature is set for the floor it has to push through. Change the floor later and the design is wrong.
- Tile where it can be tile. Bathrooms, mudroom, laundry, kitchen if you can live with it. Tile is the only floor on this list with nothing to go wrong from heat.
- Glue, do not float, over a heated slab. Floating floors need a pad, pads are insulation, and the air gap under a floating floor is worse. Glue-down engineered and glue-down LVP both outperform their floating versions.
- Read the sheet, then read it again. Surface temperature limit, radiant approval, maximum run length, humidity range. If any of those is missing, pick another product.
- Keep the total covering under about R 1. Over that the system is working against the floor. Over R 2 the floor is a mistake unless the house is very tight.
- Do not run electric mats under floating floors unless both the mat maker and the flooring maker say yes in writing. Electric heat is hotter and less even than a slab. Electric mats belong under tile.
Questions people ask
What is the best flooring for radiant floor heating?
Porcelain tile over an uncoupling membrane. It transfers heat almost perfectly, has no temperature limit worth worrying about, and does not move. Glued-down engineered hardwood is the best of the warm-looking floors, with the sheet’s 27 to 29 C cap as the warranty line.
Can you put carpet over radiant heat?
Yes, but you lose a lot of heat output. Carpet and pad together are R 2 to R 4, which is more insulation than every other floor combined. If you must, use a thin carpet and a dense radiant-rated pad, and tell the heating designer so the water temperature is set for it.
Does vinyl plank work over radiant heat?
Most rigid-core (SPC) vinyl plank is rated for hydronic radiant, with a 27 to 29 C cap on the sheet. Glue-down is the better choice over a slab. Check the sheet for a radiant approval and a maximum run length, and be careful with dark planks in a south-facing window.
What temperature should a radiant floor be?
On our slabs the water goes in at about 40 C and the floor surface runs 30 to 37 C. Wood, laminate and vinyl sheets cap the surface at 27 to 29 C and the warranty rides on that; above it you are trusting experience and the product. Under tile the limit is comfort, not the product.
Is laminate OK over radiant heat?
Most laminates are approved for hydronic radiant with a 27 C cap on the sheet and the manufacturer’s own underlay. The core and underlay together are about R 1, so the slab has to work harder. It is a usable floor over radiant and not a good one.
Check your floor against your system
The radiant flooring compatibility checker takes the floor you want and the heating system you have, or are planning, and gives you a yes, a no, or the conditions. The hydronic radiant cost page prices the system itself; this section prices what goes over it.
Sources and further reading
- National Wood Flooring Association: the installation guidelines every hardwood warranty points to: subfloor flatness, moisture limits, acclimation, fastening schedules and the radiant-heat chapter.
- Tile Council of North America: the TCNA Handbook methods for tile over wood, concrete and in showers, and the ANSI lippage and grout standards a tile setter is held to.
- Uponor Canada: hydronic radiant tubing and controls; their design manual is where the surface temperature and floor R-value tables come from.
