A floor support includes a base having a bottom surface and a top surface; a plurality of bosses arranged in an ordered array on the base, the ordered array configured to provide multiple options for routing an electric heating cable among the plurality of bosses; and a thermal insulation layer adjacent the bottom surface. Each of the plurality of bosses includes an upper surface; a perimeter wall extending from the upper surface to the top surface, the perimeter wall sloping underneath the upper surface; and an interior wall sloping continuously toward an interior of the boss as the interior wall as the interior wall extends from the upper surface to the top surface.