A water-impermeable membrane assembly for sealing a surface of a substrate comprises a waterproofing sheet and a plurality of conduits having openings in at least a first major surface, and a leak-alarm circuit disposed at least partly within said equipment space, the leak alarm circuit having a leak-alarm target operative to trigger activation of the leak-alarm circuit when in contact with a water-containing liquid. The leak-alarm circuit comprises an electronic circuit comprising a transmitter and a battery for transmission of a signal. The assembly also includes a capillary pathway disposed within at least a portion of the conduits, including at least one conduit in fluid communication with the equipment space and with respective openings disposed in at least said first surface, so as to provide a pathway for transport of a water-containing liquid by capillary action from said openings to said leak-alarm target.