Abstract: A system for locating a leak in a building layer comprises a sensing module comprising a cell having a major surface juxtaposed a first surface of the building layer and incorporating mutually spaced electrodes defining a sensing path extending parallel to the cell major surface. Sensing circuitry cooperates with the cell and applies a voltage between the cell electrodes to measure an electrical property. A probe is applied to a second surface of the building layer opposite the first surface and applies a voltage between at least one of the cell electrodes and the probe to measure an electrical property. Control circuitry detects the presence of a leak within the portion of the first surface based on a first measurement; and locates a point of leakage based on a second measurement from the sensing circuitry of the electrical property between the probe and the cell electrodes.