First, measure the actual heated area, not the total square footage of the room. Do not lay heating cables under cabinets, furniture or appliances.
Next, decide on heat output. When installing Mapeheat Cable with Mapeheat Membrane: A 3-pillar spacing in Mapeheat Membrane produces 10 W per sq. ft. (low output), which is not typically recommended but is acceptable for low-use areas when trying to stretch coverage. A 2-pillar spacing in Mapeheat Membrane produces 15 W per sq. ft. (high output), which is best for installations on a concrete slab or when heat loss is a concern. An alternating pillar spacing of 2-3-2 in Mapeheat Membrane produces 12 W per sq. ft. (standard output).
When installing Mapeheat Cable with Mapeheat Cable Guides: A spacing of 3" in Mapeheat Cable Guides produces 12 W per sq. ft. (standard output). Alternating spacing of 3"/2" in Mapeheat Cable Guides produces 15 W per sq. ft. (high output), which is best for installations on a concrete slab or when heat loss is a concern.
Always default to the lesser square foot on the chart.
Before removing the heating cable from the packaging, measure and confirm the intended square footage of your heated area. Use the coverage chart on the cable box to determine which cable spacing will yield the desired square footage. Note that consistent spacing between the cable and across the room must be maintained for even heat distribution. If you have too much cable left over, double-check that you have purchased the right cable based on the square footage of the area. If the wrong cable was purchased, contact the distributor to see if a return is possible. Otherwise, install any excess heating cable in buffer zones (such as behind the toilet) or in areas not previously calculated; or, install the cable tighter to the perimeter.