A 3D liquid detection sensor, liquid-sensitive building material, and liquid detection systems have been provided. The 3D sensor comprises a 3D liquid detection field and an electrical connector to supply a resistance measurement responsive to liquid in the detection field. In one aspect, the 3D liquid detection field includes a first plurality of pins having a distal end electrically connected to a first electrical contact of the electrical connector, and a second plurality of pins having a distal end electrically connected to a second electrical contact. In one aspect, each pin includes a building material attachment barb attached to a pin proximal end. This permits the sensor to be fixedly mounted in drywall or ceiling tile, for example. More specifically, the 3D detection field may include a dielectric sheet (either rigid or flexible), and electrically conductive traces formed overlying the dielectric sheet, with pins extending from the traces.