Getting Started: Heated Floor
Basement bathrooms always get cold, especially in Pittsburgh. So we decided to add NuHeat, which comes in both a cable and mat system. Cables need to be self-leveled, and since this bathroom floor wasn’t exactly perfect we killed two birds with one stone.
Layout the location of the NuHeat cable guides, keeping in mind they need to be 1 to 6 inches from the wall and any furniture, e.g. vanity cabinets. Guides also have to be 6 inches from the toilet flange, primarily because heat will melt the wax ring.
Use a hammer drill and tapcon or masonry bit to drill holes for the guides. Tapcon kits usually come with a masonry bit, 1-1/4″ tapcon screws are good for this project. That said, we used plastic inserts and screws; so those are also an option.
Secure cable guides with the tapcon screws using a drill or impact driver.
Prime the existing concrete floor before adding the NuHeat cables and self-leveler; this is necessary for proper bonding of the self-leveler to the concrete. Also, use the primer that’s made by the manufacturer of the self-leveler, e.g. we used Ardex P51 primer.
Use a sponge and gloves to apply the Ardex P51, it’s easier to apply the primer before the NuHeat cables. Start at the shower entrance and work your way out of the bathroom. Let the primer completely dry before self-leveling or adding the NuHeat cables.
Heated floor systems all require the use of a thermostat, which also requires an electrical box. If you’re not comfortable installing the box, call a licensed electrician; fortunately Steve’s brother is one those said professionals!
Fish a cable from the electrical box to the floor; tape the cables and floor sensor together and to the cable; fish the cable up to the electrical box.
Tuck the floor sensor into the box and install the NuHeat wire in the cable guides, spacing it every 3 stud bays. Again, the wire needs to be 6 inches away from the toilet flange; we can’t stress that enough since nobody wants a leaky toilet bowl.
Finally, the floor sensing probe should be evenly spaced between the wires, not near a heating source and at least 12 inches into the heated area. Secure it to the concrete using the same guide and screws that were used for the cables.
Add 2×4 wood blocking at the shower pan entrance and doorway to prevent floor leveler from going into the pan and outside the bathroom. It’s easier to watch the video than for us to explain it in words.
It doesn’t matter how high the blocking is, it just has to be high enough for the self-leveler to be contained in the bathroom.
Shop vac any debris from the floor and apply latex caulking to the bottom of the blocking to prevent the leveler from oozing out. It’s amazing how sneaky leveler can be, it will find every crack and find a way to invade the space next to the bathroom.
Use sill plate foam along the perimeter of the room; staple it to the drywall for a 1/8″ expansion and contraction joint between the leveler and drywall. Once the self-leveler sets the foam can be cut using a utility knife
Test NuHeat Wires
NuHeat cable resistance must be tested before, during, and after installation to validate NuHeat warranties. Yes, this is a royal pain in the butt; however, it’s a necessity to CYA and call NuHeat out on any defects in their material.
Both a resistance and insulation test should be done. Follow the NuHeat instructions for this as they could possibly change over time.
We do share how to do this test in the video tutorial.
Ardex makes some of the best products in the world. But they can be super hard to find. That said, it’s well worth your time to find Ardex Liquid BackerBoard as it can be used to level floors up to 1-1/4″ in height.
Mix Liquid BackerBoard per Ardex and measure the water per the instructions, then mix to the required RPMs and time constraints; Ardex tests these instructions and following them will ensure the product works properly.
We used the Ardex mixing kit, it’s not necessary, but comes with everything required to mix the leveler; gauging tool, squeegee, measuring buckets, mixing paddle, and barrel…it’s awesome.
You could also use a garbage can but clean it thoroughly.
We mixed two bags of liquid BackerBoard at a time; always use a silica dust respirator and safety glasses.
Pour the liquid BackerBoard over the wires and concrete floor. We just needed to cover the wires, if you need to really level the floor, add screws at the height required and set the leveler accordingly.
We continued to add the leveler until the wires were covered; liquid backer board is very easy to use and squeegee over the concrete floor.