Ceramic, stone and glass floors are attractive and durable alternatives to the usual wood, carpet or vinyl floors. However, these natural surfaces are unfortunately cold underfoot. Winter heating sources do not solve the problem and summer air conditioning makes it worse.

For a quiet, unseen addition that adds a comfortable feeling to a naturally cold floor, installation of electric radiant floor warming systems could not be easier. Electric floor warming systems install easily and economically. While electric floor warming comes in many different configurations, the heart of any of the systems is an energy efficient heating cable installed directly underneath the floor finish. It gently warms the tile, stone or glass to a temperature controlled by the specially designed thermostats.

What makes radiant floor warming so attractive? Probably the single most important element is that the systems are virtually invisible, install directly beneath the final floor finish and eliminate the need for transition changes from room to room. Tile, stone or glass are excellent heat conductors, so the warmth will be evenly dispersed over the entire heated floor space. In truth, the only visible part of the electric floor warming system is the thermostat, and you can even hide that in a closet or cupboard if you choose.

There are many types of electric floor warming systems on the market today. While each has it’s own unique product features and benefits, for the purpose of this article, we will simplify these types into three main groups.

• Free Form Cable Systems
• Roll-out Mat Systems
• Blanket Systems

Free Form Cable System

Free Form Cable Systems provide flexible, full coverage installation by lacing the cable across the room in predetermined patterns to cover all areas of the floor requiring warming. These systems consist of a low profile, flexible heating cable encased in a durable outer protective coating that provides protection during the installation process. Free form cables are easy to lay out on the floor and even easier to correct during the installation process. Free form cables are exceptionally adaptable for today’s trendy curved bathroom fixtures or meandering walls.

Roll-Out Mat Systems

Roll-Out Mat Systems are quick to install due to the nature of their cookie cutter design. Generally, mats are fabricated with the same low profile, flexible heating cable but are adhered to an open weave mesh to make the installation process quicker. These pre-formed roll out mats can be flipped and turned during installation to quickly fill a square or rectangular shaped room. They are adaptable for spot warming applications in larger rooms as well as commercial projects where format repetition is a huge benefit to installers.

Blanket mat systems are custom designed mats that fit to the exact floor dimensions of the room, including rooms with angles and curves. By being pre-built to the measurements provided by the customer, they are virtually guaranteed a perfect fit. Blanket mats usually have a very low profile and the mat itself is denser than the roll out open weave mesh, which is why they are termed “blankets.”

Installation Methods

Installation of radiant electric floor warming systems is traditionally a multi-trade project. Normally, the tile setter or floor covering installer installs the floor warming system and a certified electrician takes care of the electrical hookups for the thermostat. Electricians must follow all applicable national (CEC and NEC) local electrical and building codes regulations and inspection procedures while tile and floor covering installers should follow the guidelines of the Tile Council of North America in the U.S. and the Terrazzo, Tile and Marble Association of Canada.

With the increase in demand for tile, stone and glass floor finishes, it is important to understand the floor warming installation processes for each type of substrate, application or product available. To ensure a professional quality installation, every project should begin with the following “cast in stone” premises.

Basic Rule #One: Follow the manufacturers directions for installing any type of substrate, whether it’s double layer plywood, cement backerboard or a concrete slab.

Basic Rule #Two: Follow the manufacturers directions for installation of thin-set mortar, self-leveling underlayments and grout.

Basic Rule #Three: Follow the manufacturers directions for installation of all floor-warming systems.

Now that we’ve cleared that mystery up, follow these basic guidelines when installing any radiant electric floor warming system.

Installations Over: Double layer 5/8” (15.85 mm) exterior grade plywood substrate 16” (40.64 cm) o.c.; 1/2” (12.70 mm) cement backerboard over 3/4” exterior grade plywood substrate 16” (40.64 cm) o.c.

All surfaces should be between 40°F (4°C) and 90°F (32°C) and structurally sound, clean and free of all dirt, oil, grease, paint, concrete sealers or curing compounds.

Expansion joints shall be provided through the tile work from all construction or expansion joints in the substrate. Follow ANSI Specification AN – 3.8 “Requirements for Expansion joints” or TCA Detail EJ171 “Expansion Joints.” Do not cover expansion joints with mortar.

When installing floor-warming systems over a plywood or cement backerboard surface, be sure that the substrate is strong enough to support a tile or stone floor finish. Installers must verify that deflection under all live, dead and impact loads of interior plywood floors does not exceed industry standards of L/360 for ceramic tile and brick or L/720 for stone installation where L = span length.

Free form cable systems on plywood or cement backerboard

Installing Strapping for Free Form Cable systems on plywood or cement backerboard: Install the strapping onto the floor by following your preplanned sketch. Outside runs of strapping should be positioned so the tab clips will close towards the outside of all cable turns. Secure strapping to plywood or cement backerboard with staples or wood screws following manufacturer recommendations. Fasten the first end of the strapping to substrate. Staple or angle a screw to the opposing end of the cable to pull strapping tight to floor.  Insure the strapping is snug against the floor. Install strapping on all perimeter runs of the room first. Then install subsequent runs of strapping at 30” to 36” (76cm to 91cm) intervals between the perimeter runs.  Install extra staples or screws every 12” to 18” (30cm to 45cm) for center runs of strapping and every 5” to 8” (12.7cm to 20.3cm) in outside runs.

Installing Free Form cable into strapping: When routing heating cable to the beginning of the strapping, use clips to attach heating cable to the subfloor. Wind the cable at appropriate intervals and snap into the strapping slots. Then carefully turn the cable and snap into the next appropriate slot. Do not extend cable beyond the edge of the strapping. Close the first one or two hinged clips on strapping in order to hold the cable secure before proceeding to the next strapping run. Subsequent clips should be left open until cable placement is completed. Once the cable layout is completed, close all hinged clips, including the hinged clips not used, to securely fasten the cable to the floor, and flatten the height of the system prior to application of the thin-set. Use additional clips provided to fasten down any part of the cable that is not snug to floor. Please note than some strapping styles available simply laces like shoelaces, so closing the clips might not be required.

Roll Out mat on plywood or cement backerboard

Installing Roll Out Mat on plywood or cement backerboard: The heating cable portion of the roll out systems is adhered onto lengths of mesh mats that make it quick and easy to cover a large area. These mats can be angled, turned or completely flipped around in order to cover the space by cutting only the mesh, and moving the remaining sections of mats in a new direction In doing this, you are creating as much walkable heated area as possible. Once the mat is fitted to the area being installed, you can affix the mat to the floor in two different ways. Many mat systems come with an adhesive backing. Simply press the adhesive side of the mat onto the substrate and apply your thin-set. Other systems come with clips or staples that attach the mesh to the floor similar to the Free Form Cable Systems. With all mat systems, it is not recommended to attach the actual heated cable to the floor. Always adhere the mesh portion.

Installing Blanket Mat System on plywood or cement backerboard slab: Because most Blanket Systems are custom fitted to the room, you simply lay the system in place and apply the thin-set adhesive.

Installing thin-set adhesive or self-leveling underlayment for all Floor Warming Systems: Comb on thin-set mortar with the flat side of the trowel, taking care not to nick the heating cables. Completely cover the floor-warming system with thin-set mortar. Let thin-set dry following recommended times on thin-set package. If using self-leveling underlayment, follow directions on manufacturer package.

Installations Over Cured Concrete Slab

When installing floor warming systems over a cured concrete slab, rough or uneven concrete surfaces should be made smooth with a Portland cement underlayment to provide a wood float (or better) finish. Dry, dusty concrete slabs or masonry should be dampened and excess water swept off. Installation may be made on a damp surface. New concrete slabs must be plum and true to within 1/4” (6 mm) in 10’ (3 m). Latex Portland cement mortars do not require a minimum cure time for concrete slabs.

Free form cable system on cured concrete slab

Installing Strapping for Free Form Cable System on cured concrete slab: Install the strapping onto the floor by following your preplanned sketch. Outside runs of strapping should be positioned so the tab clips will close towards the outside of all cable turns. Fasten the first end of the strapping to concrete substrates using an adhesive tape kit. Alternative installation methods include hot melt glue guns or tapcons. Ensure the strapping is adhered tightly to the floor. Install strapping on all perimeter runs of the room first. Install subsequent runs of strapping at 18” to 24” (45.7cm to 60.9cm) intervals between the perimeter runs.

Installing Free Form cable into strapping: Follow the same directions for winding the cable onto the strapping as for plywood and cement backerboard installations.

Roll out mat on cured concrete slab

Installing Roll Out Mat on cured concrete slab: Follow the same directions for adhering the mat to the substrate as for plywood or cement backerboard installations.

Installing Blanket Mat System on cured concrete slab: Because most Blanket Systems are custom fitted to the room, you simply lay the system in place and apply the thin-set adhesive.

Installing thin-set adhesive or self-leveling underlayment for all Floor Warming Systems: Comb on thin-set mortar with the flat side of the trowel, taking care not to nick the heating cables. Completely cover floor-warming system with thin-set mortar. Let the thin-set dry following recommended times on thin-set package. If using self-leveling underlayment, follow directions on manufacturer package.

Cable and mat system crack suppression systems

Installation Using Crack Suppression Systems
“Crack suppression or isolation membranes (ANSI A118.12) for thin-set ceramic tile and dimensional stone installations act to isolate the tile or stone from minor in-plane substrate cracking,” according to the 2007 TCNA Handbook.

It is generally recommended that floor warming systems should be installed ABOVE the crack suppression/isolation system to achieve full protection from the stress cracks in the substrate below. Additionally, the width of the crack suppression product should be three times the width of the tile installed over the substrate crack. Follow manufacturers installation instructions for the crack suppression system you have purchased. And of course, never staple or screw through the previously installed crack suppression systems.

Cable and mat anti-fracture systems

Installation Using Anti-Fracture Systems
There are many applications where you need to protect the entire surface area from multiple shrinkage cracks, non-structural cracks up to 1/8” (XX mm), or cover joints in plywood underlayments, cement backerboards and concrete masonry. In these cases, you would want to install a full anti-fracture layer over the entire substrate. It is also required when installing tile or stone over hydronic (water or fluids) heating systems.

In these instances, the majority of manufactures’ recommend that the floor warming system be installed BELOW the anti-fracture system for the floor finish to achieve full protection from stress cracks, contaminates and movement from the substrate below. Follow the manufacturers’ installation instructions for the anti-fracture system you have purchased.

Uncoupling membranes, a geometrically configured membrane system designed to provide air space between the tile and the substrate below, are generally used to allow independent movement between the tile and the substrate and limit the transfer of stresses. Manufacturers of this type of membrane product REQUIRE that the floor warming system be installed underneath their membranes.

Cable and mat waterproofing systems

Installation Using Waterproof Membrane Systems
“There is a wide variety of built-up membranes, single-ply membranes, non-metallic, lead or copper waterproofing, as well as liquid applied waterproof membranes available for use with both vertical and horizontal thin-bed (ANSI A118.10) and thick-bed installations of tile and stone,” according to the TCNA 2007 handbook.

Regardless of the type of waterproofing system purchased, there is no debate on this process. The floor warming system must be installed UNDERNEATH the waterproofing system to protect the floor warming system from water damage and electrical shock. Follow the manufacturers installation instructions for the waterproofing system you have purchased.

In closing, remember that this article is meant as an overview of the general steps involved during the installation processes for electric floor warming systems. Always remember to read the written installation instructions included in your product before you begin. Consult your local electrical inspector prior to beginning your installation, as additional electrical inspections may also be required during the installation depending on local building codes. Familiarize yourself with the safety warnings included in the instructions. Radiant electric floor warming systems not only provide quiet, efficient and even warmth to the floor but require no maintenance, do not disperse dust or provide areas for mold growth. Once installed, electric floor warming is not seen or heard or worried about, it just feels really, really great!