some embodiments the protrusions 2 a may be formed from the base material 6 and as such may have a wall thickness approximately equal to that of the base thickness 6 a fig3 shows a detail cross sectional view of an area of the underlayment 1 in accordance with embodiments of the present disclosure in one embodiment the areas adjacent to each protrusion 2 a can form a heating element receiving cavity 3 each heating element receiving cavity 3 can include an interference fit 8 or contained area to hold a heating element 5 or wire in place in some cases the heating element 5 may be inserted into the heating element receiving cavity 3 with a predetermined amount of force required to part e g elastically deform plastically deform flex and or deflect etc at least one of the receiving surfaces 9 of the cavity in one embodiment when the heating element 5 is inserted into the heating element receiving cavity 3 the at least one of the receiving surfaces 9 may return to an original position thereby closing the heating element receiving cavity 3 and containing the heating element 5 fig4 shows a detail plan view of a routing hub 2 of the underlayment 1 in accordance with embodiments of the present disclosure the heating element receiving cavities 3 are shown disposed between protrusions 2 a and or routing hubs 2 in some embodiments one or more of the heating element receiving cavities 3 can be configured differently from another heating element receiving cavity 3 for instance several heating element receiving cavities 3 may be configured to provide a frictional fit for holding a heating element 5 while other heating element receiving cavities 3 may be configured to merely contain a.