Hymenochaete rubiginosa is saprobic on hardwood. It's perennial. Its growth form is effused-reflexed and the caps fuse laterally. The individual caps are about a millimeter thick and can extend several centimeters outward from the substrate. The cap has concentric bands and can be tomentose or glabrous. These were glabrous. The colors of the cap can be ochre-brown, reddish brown, or, like these, dark brown. The margins are a lighter color. The fertile surface lacks pores and is grayish with warts and bumps.
The similar Hydnoporia tabacina has a woolly upper surface and is more yellow and orange.
Hymenochaete means "hairy membrane," and rubiginosa means "rust-colored."