Floor underlayment for retaining heater cable

1. A membrane for decoupling heated flooring from a subfloor, the membrane comprising:

a flexible base; and

a plurality of projections formed into the base and extending outward from the base, each projection of the plurality of projections having:

a perimeter wall defining a height of the projection and having a plurality of sides each intersecting with two other of the sides;

a top surface integral with the perimeter wall; and

exactly one flange portion extending from one of the sides of the perimeter wall;

the plurality of projections arranged so that:

each projection has, selected from the plurality of projections, a plurality of adjacent projections, and forms with each adjacent projection a corresponding channel of a plurality of channels;

for each channel of the plurality of channels, the corresponding flange portion of at most one of the projections forming the channel extends over the channel such that the channel retains a first heater cable for heating the heated flooring; and

the corresponding flange portion of each projection does not face the same direction or the opposite direction of any of the corresponding flange portions of the plurality of adjacent projections.

2. The membrane of claim 1 , wherein in each of the plurality of projections, each of the plurality of sides has a planar portion, the flange portion of the projection extending from the planar portion of one of the plurality of sides, and wherein the plurality of projections are further arranged so that the plurality of channels facilitate retention by the membrane of one or more heater cables traveling in a plurality of directions across the membrane, the one or more heater cables including the first heater cable.

3. The membrane of claim 2 , wherein the corresponding plurality of sides of each of the plurality of projections cooperate to give the perimeter wall of the projection a substantially triangular shape.

4. The membrane of claim 2 , wherein the corresponding plurality of sides of each of the plurality of projections cooperate to give the perimeter wall of the projection a substantially trapezoidal shape.

5. The membrane of claim 4 , wherein the perimeter wall of each of the plurality of projections further comprises a plurality of rounded corners each disposed between a pair of adjacent sides of the plurality of sides, the plurality of rounded corners enabling the first heating cable to maintain contact with the perimeter wall as the first heating cable is bent around the projection.

6. The membrane of claim 1 , wherein the plurality of projections are further arranged so that the plurality of channels facilitate retention by the membrane of a plurality of heater cables traveling in four or more directions across the membrane.

7. The membrane of claim 6 , wherein the plurality of heater cables includes the first heater cable having a first diameter and a second heater cable having a second diameter different from the first diameter.

8. The membrane of claim 7 , wherein each of the plurality of channels is configured to retain any of the plurality of heater cables having a diameter between about 4.1 mm and about 4.75 mm.

9. The membrane of claim 1 , wherein:

the perimeter wall of each projection of the plurality of projections defines an interior of the projection;

the top surface of each projection is a substantially planar surface extending over the entirety of the interior of the projection; and

each projection further comprises a slit disposed through the top surface to allow transmission through the membrane of one or more of a gas, a liquid, and a flooring adhesive, the corresponding slits of two or more of the plurality of projections forming a straight line from a first end of the membrane to a second end of the membrane opposite the first end.