A system for detecting and locating a leak in a building layer , the system comprising: at least one sensing module comprising: - at least one cell having a major surface juxtaposed to a portion of a first surface of the building layer and incorporating at least one pair of mutually spaced electrodes defining a sensing path extending parallel to the cell major surface ; and - sensing circuitry cooperable with said cell and configured to apply a voltage between the cell electrodes to measure an electrical property therebetween, said sensing circuitry being further cooperable with a probe arranged to be applied to a second surface of the building layer opposite said first surface and being further configured to apply a voltage between at least one of the cell electrodes and the probe to measure an electrical property therebetween; and control circuitry operatively associated with said sensing circuitry and configured to: - detect the presence of a leak within the portion of the first surface based on at least a first measurement from the sensing circuitry of the electrical property between the cell electrodes ; and - locate a point of leakage within the portion of the first surface based on at least a second measurement from the sensing circuitry of the electrical property between the probe and at least one of the cell electrodes . at least one sensing module comprising: - at least one cell having a major surface juxtaposed to a portion of a first surface of the building layer and incorporating at least one pair of mutually spaced electrodes defining a sensing path extending parallel to the cell major surface ; and - sensing circuitry cooperable with said cell and configured to apply a voltage between the cell electrodes to measure an electrical property therebetween, said sensing circuitry being further cooperable with a probe arranged to be applied to a second surface of the building layer opposite said first surface and being further configured to apply a voltage between at least one of the cell electrodes and the probe to measure an electrical property therebetween; and - at least one cell having a major surface juxtaposed to a portion of a first surface of the building layer and incorporating at least one pair of mutually spaced electrodes defining a sensing path extending parallel to the cell major surface ; and - sensing circuitry cooperable with said cell and configured to apply a voltage between the cell electrodes to measure an electrical property therebetween, said sensing circuitry being further cooperable with a probe arranged to be applied to a second surface of the building layer opposite said first surface and being further configured to apply a voltage between at least one of the cell electrodes and the probe to measure an electrical property therebetween; and control circuitry operatively associated with said sensing circuitry and configured to: - detect the presence of a leak within the portion of the first surface based on at least a first measurement from the sensing circuitry of the electrical property between the cell electrodes ; and - locate a point of leakage within the portion of the first surface based on at least a second measurement from the sensing circuitry of the electrical property between the probe and at least one of the cell electrodes . - detect the presence of a leak within the portion of the first surface based on at least a first measurement from the sensing circuitry of the electrical property between the cell electrodes ; and - locate a point of leakage within the portion of the first surface based on at least a second measurement from the sensing circuitry of the electrical property between the probe and at least one of the cell electrodes . <EOS>