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Radiant Floor Heating Systems

Thanksgiving and Christmas are bearing down on you. When I still was building and remodeling six days a week, I clearly remember how customers wanted me gone and out of their homes during this festive season. The stress level that accompanies turkeys, family, gift giving and parties is already high enough so the dust, plastic barricades and disruption that is part of remodeling is not a welcome guest in most homes. Now is not the time for you to start a project.

You and I both know that Old Man Winter is lurking in the shadows and just after New Year's Day, he could visit you with those ice-cold bathroom and man-cave floors. Brrrrrrrr! Now's the time to plan to fulfill that nagging resolution you've made in past years to install warm, affordable and luxurious radiant floor heating when you tackle that upcoming remodeling project.

Hot Water or Electric?

There are two avenues you can pursue when it comes to creating toasty warm floors that sooth the soul and your feet. Hot water radiant floor heating systems are the darling of new construction as they can be easily installed when there's no drywall or plaster in the way.

Remodeling contractors and serious DIYrs working in existing homes tend to lean towards electric radiant floor mats. These systems are very easy to install. The thin mats that contain radiant heating cables are sandwiched between the finished flooring and the subflooring that's already in place in your home.

The labor costs to install a hot water system are exponentially higher than the electric mats. An electric mat can often be installed in a standard bathroom in about two hours or less. A plumber trying to install a hot water system might spend that much time pulling the permit!

Hot water systems require tubing be installed under the floor you're trying to heat. There needs to be a source of the hot water, and this often is a new small water heater that's dedicated to the task of keeping your feet warm. A recirculating pump is also part of this system. All of this equipment requires some space in your existing mechanical room.

The electric radiant floor mats have no moving parts and only require that a new separate electric cable be run to the room where the mat will be. This new electric circuit is usually fairly easy to extend from your main electric circuit panel. The only other task is to install an electric box on the wall that will house the computerized thermostat that manages the flow of electricity to the mat.

What Types of Finished Flooring are Compatible?

The good news is that just about any finished flooring material works on top of radiant heating. Ceramic tile, marble, granite, slate, laminate flooring, and other engineered flooring materials all play nicely with radiant floor heating. As always, research the specifications and requirements with the finished flooring before you get started.

The primary issue you might have with radiant floor heating with a finished floor is the expansion and contraction that is a byproduct of the heating cycle. When the radiant system is activated, it gets warm. The floor temperature could approach 100 F or so depending on what your system is. This rise in temperature can cause materials to expand.

When the thermostat is satisfied, the radiant floor starts to cool down. This, by default, produces contraction in the finished flooring. You simply need to ensure you install the finished flooring, per its written instructions, to account for this slight back and forth movement.

The Installation Process

I had the good fortune to install one of the electric radiant floor mats in my man cave ham radio shack last year. I ordered the mat online by telling the company the size of my room, they made it in days and it was shipped directly to my home with the required thermostat and all installation instructions.

One of the coolest parts that was included was a computerized tiny monitor that was used during the entire installation process that told you if somehow the mat got damaged during one of the installation steps. Accidents can happen, but if you just exercise normal precautions, you'll not have an issue with damaging the mat.

No matter what product you decide to use, the first step in the installation process is to STOP and read the written installation instructions. Don't read just the first step and get to work. Read the entire set of instructions from start to finish and make sure you have all the needed tools and that you understand how you'll complete each step.

If you need help, most of the manufacturers have online help or you can call them to give you a verbal assist on the phone.

The instructions I used stipulated that I had to embed the electric mat in fresh thinset. Thinset is a powdered mortar that you mix with water. Once mixed with water it has the consistency of cake batter. You use a notched trowel to spread it on the subfloor.

I took the time before I mixed the thinset to inspect my wood subfloor. I wanted to make sure it was secured to the floor joists so I used my drill driver to install drywall screws every 8 inches down each joist. I also carefully felt along the top of each joist to make sure there were no nailheads or fasteners that were proud of the surface. I didn't want anything that might cut into the electric heating cables in the mat.

My instructions also said that once the mat was set in the thinset I needed to cover it with more thinset. The depth of this thinset needed to be one-quarter inch. What's more, this thinset needed to be very smooth and in the same plane so the finish flooring would end up smooth.

To get this second layer of thinset in the same plane I installed 2-inch-wide strips of one-quarter inch trim lumber along the edges of the room. I had figured all this in when I ordered the mat so the edges of the mat were about one inch from the wood strips. You need to think about this before you order your mat, so if you're in doubt, talk with the mat manufacturer before you place your order.

With the wood strips in place, I started on the far wall away from the door and started to spread the thinset in a strip as wide as the room and about 18 inches from the far wall. I had the mat rolled up and set the long edge in the fresh mortar and started to unroll it.

I used a hard rubber grout float to press the mat firmly into the thinset. It worked well. I continued to spread thinset in a line, unroll the mat and patted it into the thinset with the rubber float. In about 30 minutes I was kneeling outside the room with the mat embedded in the fresh thinset. I checked the little monitor and the green light was on so I know I had not damaged the mat.

The next day, I applied the layer of thinset over the mat using the wood strips on the edge of the room as screed guides. I had cut a straightedge piece of lumber that was one inch less in length than the room was wide. I slid this lumber back and forth while pulling it and the thinset on the other side was in a perfect plane with the wood strips. It looked gorgeous!

It only took about an hour to add this extra layer of thinset. I took my time to ensure there were no humps or low spots. It's so important for this layer of thinset to be smooth and in the same plane. Once again I checked the little monitor and the green light was still on.

At this point, you're almost finished. You need to allow the thinset mortar to dry a few days if you're installing a wood floor over it. You don't want all the water in the thinset soaking up into the wood flooring.

My instructions called for a temperature probe to be installed near the wall thermostat. This probe needed to be installed just under the finished flooring. Since I was installing laminate flooring, it was very simple to place this probe.

My mat has been keeping me toasty warm up in my secret man cave above my garage for a year now. I love the computerized thermostat that's programmable. It allows me to save lots of electricity by just turning the mat on before I plan to be in the room. It then turns the mat off an hour or so before I intend to go back into the house. The thermostat has a manual override if you want to change the room temperature for any reason.


You're going to love radiant floor heat. It's silent, it's warm and it works. Radiant heat is considered by many to be the ultimate heat. It's what you feel when you stand in the sun, it's what you feel in front of a campfire and it's going to make you one happy camper when you walk into your bathroom on a frigid winter morning.


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