Flooring underlayment

A flooring underlayment comprising:

• a) thermoformed membrane, the membrane including:
• i) a panel having a panel top surface for supporting a finished flooring material and a panel underside surface opposite the panel top surface;
• ii) a plurality of dimples projecting from the panel underside surface, each dimple having a closed dimple lower end spaced apart from the panel underside surface by a dimple height;
• iii) a plurality of grooves open to the top surface for receiving at least a portion of an elongated heating element therein, each groove formed within a groove body projecting from the panel underside surface, the groove body having a closed groove lower end spaced apart from the panel underside surface by a groove height that is between 30 percent and 90 percent of the dimple height;
• and
• b) a fabric sheet having an upper surface releasably adhered to the dimple lower ends of the plurality of dimples by respective frangible bonds, and a lower surface for anchoring in a layer of adhesive mortar applied to a subfloor surface, the frangible bonds facilitating decoupling of the membrane from the fabric sheet after installation to isolate the finished flooring material from shifting forces exerted between the subfloor and the membrane;
• wherein the dimples are arranged in a matrix of rows and columns, and the groove bodies extend in a straight lines spaced apart from the dimples, and wherein a ventilation gap is provided between a lowermost surface of each groove body and the upper surface of the fabric sheet, the ventilation gap beneath each of the plurality of groove bodies providing fluid communication between space around adjacent dimples on either side of each groove body for facilitating evacuation of moisture from beneath the membrane.

A method of installing flooring, comprising:

• a) applying an adhesive mortar first layer to a subfloor surface;
• b) laying a flooring underlayment on the adhesive mortar first layer, the flooring underlayment including a fabric sheet releasably secured to closed ends of dimples projecting downward from a panel underside surface of a membrane body panel, the laying step including anchoring a lower surface of the fabric sheet in the adhesive mortar first layer, the dimples having dimple sidewalls defining a dimple height extending vertically from the panel underside surface to a dimple lower end of each dimple, and the dimples holding the membrane body panel above the fabric sheet;
• and
• c) installing an electrical heating cable in a groove of the membrane, the groove open to an upper surface of the membrane body panel and formed within a groove body projecting from the panel underside surface, the groove body having a closed groove lower end spaced apart from the panel underside surface and the groove body having a groove height extending from the panel underside surface to the closed groove lower end, wherein the groove height is between 30 percent and 90 percent of the dimple height, and wherein a ventilation gap is provided beneath a lowermost surface of the groove body and an upper surface of the fabric sheet.