An electrical box includes a front surface having an opening providing access to a hollow interior of the electrical box, at least one sidewall extending rearwardly from the front surface to form the hollow interior, and a seal disposed on an exterior surface of the at least one sidewall. The seal has a triangular cross-sectional shape including a thin end configured to first enter an opening of a building structure receiving the electrical box therein. A tapered surface of the seal is compressed as the electrical box is received into the opening in the building structure to provide a seal around an exterior surface of the at least one sidewall of the electrical box.