Installation Case Study: Radiant heat revives residential bathroom
Utilizing an electric floor heating system in a bathroom over an unheated crawl space, a Michigan homeowner regained comfort and functionality
After years of living with a cold bathroom located above an unheated crawl space, a homeowner in the Lansing, MI, area decided to make a change. Because her bathroom also was due for some updating, the homeowner opted for a full bathroom remodel, complete with heated floors and a curbless shower.
The homeowner chose a curbless shower for its modern, seamless look. However, curbless showers are also useful for universal design purposes, as they are accessible by people of all ages and abilities. Without a threshold to step over, homeowners can effectively “age in place” in their homes. This is a big selling point for many homeowners, whether they’re considering resale or not.
No matter if it’s used inside or outside of a shower, tile is inherently cold. When it’s used in a bathroom located above a crawl space, it becomes even colder. That’s why this homeowner decided to heat her entire floor — shower and all — during her bathroom renovation. To make sure the heating system and subfloor would not be susceptible to water damage, she opted to have it waterproofed.
For her heating needs, the homeowner turned to WarmlyYours, based in Lake Zurich, IL. The company got the project started with a custom installation plan, which specified the room’s dimensions, how the heating cable should be laid out, where the thermostat should be located, as well as the location of permanent fixtures. The entire bathroom measured 60 square feet, with 50 square feet of heatable space (not taken up by permanent fixtures or too close to walls). As a result, WarmlyYours quoted two heating cables, one thermostat and a 54-square-foot Prodeso Installation Membrane with ProBand waterproofing accessories. One 40-foot heating cable was dedicated to the shower floor, while the other 120-foot cable was devoted to the rest of the bathroom. This resulted in the power requirements being 5 amps and 592 watts, which meant only one 15-amp non-GFCI breaker was required.
To complete the work, the homeowner hired a professional tiler. With materials in hand, the first step in the process was to test the heating elements to ensure they were working properly. The tiler used a digital ohmmeter and Circuit Check to test the system on site. After confirming that the system was in good working order, it was time to plan the layout of the Prodeso Installation Membrane. Using the tried and true method of “measure twice, cut once,” the installer dry fit the membrane to the floor, making sure that the square-shaped “studs” on each piece of the membrane lined up perfectly with the others. This ensured that the heating cable was properly spaced.
Next, because the subfloor was made of plywood, the installer used a latex-modified Portland cement thinset mortar to adhere the membrane to the subfloor. The Prodeso Membrane features vapor management properties that allow the thinset to dry and cure properly while keeping any moisture from the subfloor in check.
With the membrane installed, the tiler ran the floor heating system’s cold lead and sensor wire to the electrical box where the thermostat would be installed. Then, he began pressing the heating cable between the membrane’s “studs” in a serpentine pattern, per the WarmlyYours installation plan. When he was finished, he placed the floor sensor parallel to a section of heating cable to relay the floor temperature back to the thermostat. Then, he confirmed that the sensor was working properly by testing it with a digital ohmmeter.
With the floor heating system in place, it was time to waterproof the system. Using ProBand waterproofing accessories from WarmlyYours, the tiler adhered the material to all seams of the membrane as well as along the edges and corners of the room and shower. This preventative step ensured that any water on the floor would not seep through to the subfloor.
Once the waterproofing materials were in place, the tiler spread unmodified thinset across the floor and immediately began the tile installation. Typically, a layer of thinset or self-leveling cement must be spread over the heating element and completely dry in order to hold the heating element in place before the tile installation can start. When using a Prodeso Installation Membrane, there is no wait time between installing the heating cable and installing the tile because the membrane is already holding the heating element in place. Therefore, there’s no need for an extra layer of thinset or self-leveling cement over the heating element and, therefore, no wait time. As a result, this project was expedited, making it possible to complete this flooring project in only one day. This benefit, combined with the membrane’s ability to be waterproofed and prevent cracking in the tile above, are the reasons why the homeowner chose this particular floor heating installation method.
The homeowner selected large-format tiles for the bathroom floor and mosaic hexagonal-shaped tile on mesh backing for the shower floor. For the large-format tile, the installer used a tile leveling system to ensure that the floor was completely level. Then, he tested the system one final time to make sure it was in good working order.
Once the homeowner got the green light, she had a licensed electrician install the thermostat and finish the job.
In the end, the homeowner was left with a bathroom that finally felt as warm as the rest of the home.