A joist has a front surface and first and second opposite side surfaces. The side surfaces extend in a rearward direction from the front surface. They also extend in a lateral direction perpendicular to the rearward direction. An electrical box has a hole configured to receive a fastener that fastens the box to the first side surface. The box further has a side wall and a rear wall together defining a cavity that is isolated by the box from the hole. The cavity is configured to extend along both side surfaces of the joist and to contain electrical connections. The side wall extends laterally beyond the hole and the rear wall is located rearwardly beyond the hole.</SD OAB>
