How to Install Electric Radiant Heating Wire on a Cement Slab
Using electric radiant floors as a supplemental heating source in a room has become very popular in the last few years. We’ve decided to install 1000 sq. ft. of electric radiant heat in the basement of our house to take the cold edge off the concrete slab, which otherwise stays a brisk 55 degrees all year round.
When installing electric heating wires on to a slab (or really any substrate), a professional installer (read: DIYer) has a vested interest in keeping the radiant heating wire and any mesh bonded tightly to the slab. A close, secure bond to the slab ensures:
- The heating wire maintains a very low profile, making it easier to cover with a thin layer of thinset or self-leveling mortar. This is advantagous because wires that stick up through the initial layer of thinself or self-leveler can be easily cut or knicked, rendering the entire heating mat useless. Also, since both SLM and thinset are expensive, the lower profile of the wire ensures a minimal amount of SLM/thinset is required, thus reducing overall cost.
- The wire doesn’t “come loose” while spreading thinset or SLM, which might move the wire in a way that compromises the installation. For instance, all electric radiant heating systems require that the heating wires never cross. Crossed wires create an unsafe condition and will likely cause the mats to overheat when they are operated. Gluing down the wires ensures they don’t move.
Most radiant heating wires are approximately 1/16″ – 3/32″ thick. Hot gluing the mats allows thinset or SLM used to cover the mats to be poured at a mere 1/8″ – 1/4″ thick.
Steps for Hot Gluing Radiant Heated Flooring Mats
- Lay out the mat according to your plan for the room. (All radiant heating flooring vendors will provide you a plan for how to lay out the radiant wire if you first give them a drawing of the room).
- Plug in and heat up an electric glue gun. You’ll want to use a “professional glue gun” that can take 1/2″ glue sticks. Hobby models that use 1/8″ sticks will go through glue sticks too quickly).
- Drop a pool of hot glue onto the slab under where the wire will go. Press the wire into the glue. If your slab is below-grade, it is probably 50-60 degrees. The hot glue will begin to freeze quickly, creating a tight grasp around the wire. (Note that in some places you may have to cut the radiant heating wire out of the mesh, as shown in the picture above).
- Move down the wire hot gluing the wire every 12-18″ or wherever the wire protrudes from the flat plain of the surface of the slab.
- After you finish the install, carefully recheck all the wire to ensure it is tightly bonded to the floor. Be careful walking with shoes on across the wire, as a stone or other object caught in the treads could nick the wire.
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