A heater mat for a rotor blade includes a plurality of electrically conductive heater wires extending in a path along a span of the rotor blade and a plurality of yarn thread knitted to the plurality of heater wires, each of the yarn threads looping around at least one of the plurality of heater wires. A warp thread is positioned between adjacent heater wires and knitted to adjacent pairs of the yarn threads without looping around the plurality of heater wires, to maintain spacing between adjacent heater wires of the plurality of heater wires. An electrical current flowed through the plurality of heater wires inhibits ice accumulation on the rotor blade assembly.