This has a semicircular or fan-shaped fruit body which is quite woody with a maze of gill-like ridges on the underside. This bracket is broadly attached to the substrate, and sometimes has a defined umbo. The upper surface is lumpy and warty, these often formed in concentric ridges with shades of grey, brown and buff, with paler margins. Fruit body 10 to 20cm across, 1 to 10cm thick.
Seen from spring onwards. Found on the dead wood of oaks, which causes a brown rot which attacks the heartwood. Common and widespread.