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Flooring 101 Home Tile Flooring Radiant Heat Bostik Heatstep FAQ sheet

Bostik Heatstep FAQ sheet



What makes the floor warm?

The red heating cable in the white weave of a HeatStep mat gets warm and transfers heat to the floor. The floor, in turn, transfers heat to the rest of the room. HeatStep wire does this the same way with the red heating cable attached to straps.

Does HeatStep mat and/or wire weaken or strengthen my floor?

HeatStep mats and wire have been tested by the Tile Council of North America (TCNA) to ASTM C627, officially known as "A Standard Test Method for Evaluating Ceramic Floor Tile Installation Systems Using the Robinson-Type Floor Tester". It tests for deflection under increasing weight loads on a wooden framed floor or with a concrete slab floor. HeatStep mats passed these tests for HEAVY classifications, such as shopping malls, commercial areas and etc. HeatStep mats apparently add tensile strength to the tile and mortar sandwich. When in doubt, follow TCNA and ANSI (American National Standards Institute) specifications.

Is HeatStep electric floor warming efficient?

Radiant floors warm people and objects directly without overheating the air. Electric radiant converts nearly all its energy into a usable form. Set the home thermostat lower and still be comfortable. Use a programmable thermostat and the system automatically sets back to a lower temperature when the rooms are not in use. Insulate below the floor or below the heating system and on top of the concrete slab to allow the system to respond faster and use less energy.

What does it mean that HeatStep is a very low EMF product?

EMF is the abbreviation for Electromagnetic Field, also commonly referred to as Electromagnetic radiation, or EMR. HeatStep twists two heating elements together to minimize EMF. We test our products to a protocol known as REET (Radiant Electric Emissions Test) which is conducted by an independent third party test lab known as ETL/Semko. Scientific studies vary, but recommendations suggest reducing EMF exposure.

What voltage do I need for my HeatStep floor?

HeatStep is built for 120 VAC or 240 VAC for warming larger areas. Both systems have the same efficiency. The best option is to see what power is available for your installation. 240 VAC is more common outside the United States and in commercial applications. A HeatStep thermostat can control up to 150 square feet of heated floor on 120 VAC or 300 square feet on 240 VAC.

What's the warranty on HeatStep products?

HeatStep heating elements are covered by a limited twenty-five (25) year product replacement warranty. HeatStep controls have a two year limited warranty. The HeatStep warranty is transferable to a new homeowner, unlike others. HeatStep warranties the product, not just the original homeowner.


You make different products, so which one is the best one for my application?

HeatStep mats work great in thinset or selfleveling mortar over frame floors or slabs. Normally rooms needing less than 150 square feet of heated area with square corners are the best for HeatStep mats. HeatStep wire does the same thing, but it costs less, installs with straps and can be used in the same areas. Rooms needing more than 150 square feet of heated area and/or rooms with angles or arcs are good for HeatStep wire as it easily molds itself to unusual shapes.

Specifically, how is HeatStep Wire different than HeatStep Mats?

Mats install faster in rectangular spaces and everything is preset for you. Mats add a fiber reinforcement to the thinset or self-leveling mortar which makes your floor stronger. The heating cable is attached to a white mesh mat with optimal 2.5 inch spacing and 12 watts per square foot output.

Wire costs less per square foot than the mats and the installation works well with unusual room shapes. So, wire is more popular in larger areas or rooms with angles, curves, nooks, or tight spaces that don't fit well with mats. You can adjust the spacing of the wire to match the heat loss from the room.

How much HeatStep Mat or Wire should I order?

1.    Calculate total wall-to-wall area of the room.

2.    Subtract the square footage of all built-ins (cabinets, sinks, etc.)

3.    Multiply this by .90. Round to the nearest 5 sq. ft. This is the heated area.

4.    Based on the square footage of heated area, select the appropriate HeatStep Mat(s) or Wire spool(s) from the HeatStep product listing.

Will the HeatStep system raise my floor height? How much?

Estimate 1/8 - 3/8 in (3.1 - 9.5 mm) depending on the installation method. Here are three examples:

1.    Most installers use a 1/4 to 3/8 inch notched trowel to apply thinset mortar.

If thinsetting and setting tile directly over the heating elements, estimate 1/8 - 3/8 in (3.1 - 6.3 mm) of increased height.

2.    If you skim coat thinset over the heating system first, let it dry, and then thinset the tile, estimate 1/4 - 3/8 in (6.3 - 9.5 mm added thickness.

3.    Or, you can apply 1/4 - 3/8 in (6.3 - 9.5 mm) inch self-leveling thinset to cover the heating elements and then cover with a finished floor covering material like wood flooring.

So, how much more thinset will I need for a HeatStep floor?

A safe estimate is to plan on using 60% more thinset than would normally be needed with a cold floor.

What kind of floor coverings can I put over my new radiant floor?

If you embed the heating elements in mortar, you can use many kinds of floor coverings. The most popular warm floors are tile and stone. If you cover the heating elements with a self-leveling thinset, you can install laminate, floating, or glue-down hardwood flooring.

Are there floor coverings that don't work well over a radiant floor?

Nail-down floors won't work for obvious reasons. Vinyl flooring may deform and discolor on top of the heating elements.

A pad and carpet will insulate your radiant floor so you might be disappointed with its performance. Rubber and cork floors also have higher insulating values so you may not be pleased with the warmth. Bamboo is a type of grass and you should check with the manufacturer to make sure it is rated for elevated temperatures. Although the temperature at the surface of a radiant floor should not exceed 85F (29C), the temperature at the bottom of the finished flooring could see temperatures of up to 110F (43C).

Do I need to put insulation under my HeatStep floor?

Insulation will reduce heat loss and improve your response time during warm-up periods.

If you can get it under the floor framing or under your thinset (follow Tile Council of North America guidelines), insulation is a good idea. There are a number of products made to work under thinset floors, so check your local flooring distributor or dealer.

Do you recommend a control to manage my radiant floor?

Yes. A HeatStep thermostatic control has GFCI protection and a floor sensor to set the floor temperature. It has a system on/ off switch that comes in handy and some models have programmable features to turn the system up and down, automatically, based on the entered schedule.

How much load can a HeatStep thermostat handle?

HeatStep thermostats are dual-voltage thermostats (120 VAC and 240 VAC) that are rated for up to 15 amp service. They can handle up to 150 square feet of heated area at 120 VAC (15 Amps) or 300 square feet at 240 VAC (15 Amps). For larger areas that need one control, simply add a Relay for another 15 amps of heated area.


Can I cut the heating cable if I have too much?

No. That will damage the cable. Each cable is built with a specific ohm (resistance) value, so the length must remain as it came from the factory.

Then what can I do if I have too much heating cable on the job?

If you find you have too much heating cable, you can always use of some of the excess next to the toilet or other areas you planned to leave unheated. You can adjust the loose heating cables as close as 2 inches to each other, but stay 6" away from the toilet wax ring. If your mat or wire is too long for the project, don't roll it up in the wall; that will cause dangerous overheating. Return it for one that is perfect for your project.

Can I shorten the shielded power lead? Can I shorten the sensor wire?

Yes and Yes. After you have pulled the shielded power lead and the white sensor wire into the control box in your wall, you will probably have some left over. You can cut off the excess and make the connections to the HeatStep thermostat. Never cut the heating cable or the sensor probe (the bulb at the end of the wire).

If I have heating cable left over, can I cut them or leave them in the wall?

No and Never. Never cut the heating cable. Always embed the cable in mortar in the floor and that includes the factory splice that joins it to the power leads. Never put heating cable or factory splices in the wall.

If I cut or damage the heating cable, can it be repaired?

Never cut the red heating cable for any reason. If during installation, you damage it, you can call our toll free number at 1-800-726-7845 and you can purchase a "Heating Wire Repair Kit". These kits should be installed by a licensed electrician.

How do I secure HeatStep wire strap to a slab?

Drilling holes and fastening the strap with screws is an approved method. If you have backerboard over plywood, you can use nails or screws to hold the strap. The fastest and easiest way, however, is to spray the back of the strap with high-strength spray adhesive. Hot glue is a good alternative to spray adhesive. We also include double-sided tape in our kits (or you can purchase it separately), and this works well, especially over concrete.

Why should I use both an ohm meter (multimeter) and a Wire Fault Detector?

Because these work well together. The multimeter tells you the resistance (ohms) is up to factory specifications and the Wire Fault Detector sounds an alarm if you damage the wire during installation.

The multimeter will also show a change in resistance if a wire is severed, but it doesn't sound an alarm. So, our advice is to use both devices when you install your radiant floor.


Your manual says I'm supposed to wait 2 to 4 weeks after installation to turn my HeatStep system on. Why?

Mortar requires time to cure completely. If you turn on the system before the mortar is cured, it will shrink, crack and pop up your floor covering. Refer to the instructions on the bag of masonry or call the manufacturer.

Does it take a long time for the floor to get warm?

From a cold start, the system takes a while because it's warming up the whole mass of the floor. A HeatStep thermostat helps with this because it "sets-back" the temperature to a lower level, but not completely off.

When the room is ready for the "comfort" temperature, the control will warm the floor up quickly. On average, this takes 20-45 minutes. Insulation below the floor warming system will reduce your warm-up time.

What does a programmable control do?

The programmable thermostat control lets you set a seven day schedule for your warm floor. Typically, the floor gets warm in the morning and in the evening when you are using the room. Programmable controls are popular because they start warming before you come into the room and they reduce the floor temperature as you leave. Then, you are always comfortable, but you don't waste energy.

What's a good temperature to set my radiant floor at?

The surface of your floor should not exceed 85F (29C). Your control is programmed to let your floor "set back" to a reduced temperature. If you have a wood or laminate floor surface, most manufacturers specify it should not exceed 82F to 84F (27C to 28C).

What could go wrong with HeatStep products?

The installation manual lists several things that could cause, prior to installation, harm or damage to the product. Typically, HeatStep is in greatest danger on the jobsite where sharp tools and construction traffic can damage a heating cable. Once the floor covering is installed on top of the HeatStep, there is very little that can harm it.

Contact Us: (800) 7Bostik / (800) 726-7845

S-Bostik-FAQ 1233

Flooring 101 Home Tile Flooring Radiant Heat Bostik Heatstep FAQ sheet