Polyporus alveolaris is a saprophyte that grows on dead hardwood. It’s an annual sessile species with distinct diamond shaped pores. The pore surface is white to tan and the pore size ranges between 1-2 per mm. The pores are also congruous with one another and are not maze-like. The upper surface is usually reddish yellow, but varies with location. The fruiting body has a single pileus that may overlap others. One distinct feature of this species is the dark squamules present on the upper surface. Polyporus alveolaris is usually considered to be centrally stipitate, but it often appears to have a lateral stipe. This species usually grows up to 1 cm long and .5 cm deep; however this varies considerably depending on the environment. The species has a corky texture and has a somewhat waxy, smooth upper surface.
The microscopic features include spores that are cylindrical, hyaline, and smooth. The spore size is 11-14.5 × 4-5 micrometers. The basidia are clavate with 4 sterigmata. The basidium size is 28-42 × 7-9 micrometers, with a basal clamp.