This disclosure describes devices and methods for forming voids in or adjacent concrete structures. In some embodiments, a device may include a structure. The structure may be substantially planar. The structure may include a plurality of channels extending therefrom. In some embodiments, the channels are closed at a first end distal from the structure. In some embodiments, the channels are open at a second end proximal to the structure. In some embodiments, the device may be formed from a molded pulp. The molded pulp may be configured to inhibit penetration of water. In some embodiments, the device may be configured to substantially support poured concrete during at least a portion of a curing process of the poured concrete.