2 Min. Read

Thinset vs. Self-Leveling when Installing Radiant Floor Heating

Luxury Vinyl Tile LVT Before and After with TempZone Flex Roll and Self Leveling Cement 1

If you’re not a pro and are new to installing radiant floor heating, you will likely face the obstacle of choosing either latex-modified thinset or a self-leveling compound. Both have their advantages and disadvantages, but when choosing between the two of them, it truly boils down to the type of flooring that you are installing with your radiant heat system.

Before the installation process for radiant floor heating systems begins, it’s important to understand exactly what latex modified thinset and self-leveling compound is, as well as the pros and cons of each.

Latex-modified thinset is a blend of cement, very finely graded sand, and a water retention compound that allows the cement to properly hydrate. It is used to attach ceramic tile, glass tiles, metal tiles, stone tile, and cement tiles to all kinds of substrates like concrete, plywood, and vinyl flooring.

Tile being installed over underfloor heating with thinset

Pros of Latex-Modified Thinset:

  • Very durable and resistant to cracking.
  • Less expensive than self-leveling compound.
  • Readily available.
  • No primer is required.
  • The same material to cover the wires and mesh is used to set the tiles, so there is only one item to buy.

Cons of Latex Modified Thinset:

  • If a second batch is needed, it is difficult to create the exact same consistency as the first batch.
  • Can be difficult to level evenly.
  • More labor intensive.
  • More chance of damaging wires with the trowel.

When it comes to flooring, tile installations are almost always done with latex modified thin set. If you were installing vinyl flooring, it would be more difficult to achieve a perfectly level and flat floor with latex modified thinset, so self-leveling is a better choice.

Speaking of level floors, leveling underlayment is more likely to give you a completely flat surface. Self-leveling compound is polymer-modified cement that’s typically used to create a flat and smooth surface with a compressive strength. It is used as an underlayment for many types of floor coverings requiring a flat surface, including sheet vinyl, vinyl composition tile, ceramic tile, carpet, and wood.

TempZone Flex Roll Pro Page Thumbnail

Pros of Self-Leveling:

  • It is flat (self-leveling).
  • Perfect for laminate flooring.
  • Faster installation process than latex modified Thinset.
  • Less likely to damage wires.

Cons of Self-Leveling:

  • More expensive than latex-modified thinset.
  • Primer is required.
  • Its thick density can cause the wires and mesh of the radiant heating system to float.
  • The mesh needs to be attached/stapled down every few inches.
  • Areas, such as vents and doorways, need to be dammed off.

The rule of thumb is when installing vinyl or laminate flooring; self-leveling is the ideal compound to use. By using latex-modified thinset under a vinyl (either sheet vinyl or luxury vinyl tile) or laminate floor you run the risk of the mortar being slightly uneven which can make the flooring unstable. For hardwood floors, it's usually better to use self-leveling underlayments between the sleepers. 

Now that we’ve got the basics covered, you can make an informed choice. The next step is figuring out which floor heating system to install! You can get started with a free instant quote

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This is very useful stuff!

Well done! I personally use SLU exclusively. It provides the flattest tile surface while it protects and encapsulates the wire. If you need to change 1 tile or the whole floor you may do so without the collateral damage to the floor heat system.

Linnay, Thank you sooo much for your informative read! What brand/type self leveling material do you use? Laticrete has some good reviews but I wanted to get your opinion! Patrick

I appreciate the information on the benefits of self-leveling and the benefits of of Latex-Modified Thinset. I had no idea that the Self-Leveling was less likely to damage wires when installing. My brother is looking at dong some renovations to his home within the next year or so, I will be sure to share this information with him so he can make the right decision. https://tileprodepot.com/product/laticrete-nxt-primer/

I am planning on floor heating on a remodel of a Florida room which has a slab. My plan is to put down an insulation layer, then heat cable, then thin-set then latex tile adhesive and tile. See any issues with this plan?

WarmlyYours Responds...

Chas, that sounds like a good plan but you can also accomplish this with one less "ingredient." You can use latex modified thinset as your adhesive for attaching the insulation to the slab, for embedding the heating cable, and for setting the tile. We have a cross-section drawing of the depths that you can review here: https://www.warmlyyours.com/publications/TZ-FLOOR-HEAT-3-TILE-OVER-INSULATED-CONCRETE-THINSET-A and, as always, feel free to give us a call if you have any further questions at 1-800-875-5285. Hope this helps!

We are installing in floor heating in our sunroom. The subfloor is plywood and the builder put tape to seal the seams. My question is should we use the self leveling compound down first then lay the wires and then another layer of thin set over the wires then install the engineered vinyl plank flooring down? Heather Bondy

WarmlyYours Responds...

Heather, for most applications the layer of self leveling over the subfloor will be unnecessary. But it can be useful if your subfloor has dips or is not level, as it will provide an even surface for the rest of the installation. It can also make sure your heating element ends up 1-1.5" from the top of the flooring surface for optimal performance. If your subfloor is level, you can skip directly to adhering the heating element to the subfloor, embedding the heating element in either self leveling or thinset, and then attaching your flooring. We have some great videos outlining this process and our 24/7 Tech Support Team is always available to answer any additional questions you might have.

I'm remodeling a bathroom that has under the floor radiant heat. The old tile floor had a lot of cracks so we decided to remove and re-tile. After lifting the tile, I discovered that the installer had used 1/2" plywood over the subfloor as the backer board and all of the cracks in the tile followed the seams where they had joined the 1/2" plywood together. The floor also squeaks which tells me it is probably flexing more than is good for a tile installation. The 1/2" plywood is nailed down. I'm trying to decide how to best approach this. One option is to keep the 1/2" plywood and just add a lot more screws to tighten everything up. Another is to take up the 1/2" plywood and replace it with cement backer board. This gets tricky as it looks like the 1/2" plywood was put in place before the plumbing and a hot water baseboard heater that was installed under the sink. What's the best way to deal with this? Thanks, John H

WarmlyYours Responds...

John, that's a great question and while we're reasonably certain that the cement backer board route that you outlined will ultimately be the best solution, our best recommendation for you is to have the floor evaluated by a flooring professional that you trust. There's obviously a lot of variables that would go into this assessment and there's no replacement for someone that can actually see the project up close. We hope that helps!

I'm trying to find an answer for my question and have thus been unsuccessful asking "only" concrete and "only" radiant flooring guys so here goes....building a house...we have (5"??) concrete poured on our main level. We are installing electric heat (instead of glycol) for our "full" house heating needs (no gas...just supplementing with a wood stove). To save $, we would prefer whatever we pour over it to be "the finished floor" (not putting plank, carpet, tile on top). Can thinset "be the floor"?? Can Self-leveling concrete "be the floor"?? any insight will be better than what I've got so far (big fat zero lol!). Thanks!!

WarmlyYours Responds...

Thanks for the very interesting question! It's a tricky one to answer without all of details but we can definitively say that neither thinset nor self-leveling cement would be serviceable final flooring surfaces. They're simply not durable enough for direct and continued foot traffic in that application (installed under a floor covering is a totally different story). Your best bet would be to use our Slab Heating Cables or Mats. These can be attached to your existing slab floor and then embedded in a new layer of traditional concrete, which can then be treated like any finished concrete floor. Hope that helps.

Hi, I am remodeling my bathroom and have put electric radiant floor heating in. I am now looking at just less than an inch between the level of the tile and the level of the tile in the shower pan. I am trying to do a same height walk in shower from floor to shower pan. My question is can I put about 1 inch of leveling concrete over my electric floor heating element and then tile over the top while not completely losing the heat? Thank you

WarmlyYours Responds...

Thanks for the question! Our official installation guidelines for our TempZone heating elements (the type that would be used under tile) stipulate that the heating elements themselves should be installed at a continuous depth that is no deeper than 1.5" inches from the finished flooring surface. Depending on how your floor heating is currently installed, it sounds like your project would be very close to exceeding this limit once you factor in the tiles and the additional thinset to adhere those to the self-leveling concrete. If you feel like this is the case, please don't hesitate to give us a call at a 1-800-875-5285. However, if the heating elements will be within 1.5" of the finished flooring surface, then the heating system will still be able to provide heat for the room because the heating elements essentially turn the embedding concrete/thinset into a "heat bank" that then evenly radiates heat upward through the room. You'll want to keep in mind, though, that since there will be more mass in a floor with 1" thick layer of self leveling concrete, it will take longer to reach the desired floor temperature than a system installed in a thinner level of SLC. Hope that helps!

Hi, we are looking to renovate a slab-on-grade house that has busy multi-coloured flagstone floors on top of a radiant floor system. Wondering if rather than ripping out the floors and risk damaging the heating system, I can skim coat over those floors with concrete?

WarmlyYours Responds...

You should be able to do a skim coat of concrete over the existing floors but you may notice a decrease in heat output (because of the additional material over the heating system). We would need more details about the heating system and how deeply it's installed currently along with the proposed depth of the skim coat to give you and idea of how much of a decrease that will be. Hope that helps and feel free to give a call (1-800-875-5285) if you have any other questions.

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