Water Leak Under the House? Finding Leaks in Floor Voids

Most houses built before the 1930s have a suspended timber ground floor. Joists sit on sleeper walls and boards sit on the joists. The space beneath carries the cold supply pipe, often the heating flow and return, and sometimes a hot water run to the kitchen. The void is ventilated by air bricks in the outside walls, which is why it stays dry in a healthy house. When a pipe down there weeps, the water soaks into the oversite and the base of the walls. Nobody sees it, because nobody goes down there.

The signs arrive at floor level. Boards start to cup, with their edges rising, or a board that was flat begins to creak and move. A musty smell lingers in the front room or hall and is strongest first thing in the morning. Skirting boards swell and paint lifts along the bottom of a wall. In winter the room can feel colder than it should, because wet ground beneath pulls heat out of the floor. In the terraces of Watford, Harrow and inner London these signs are easy to blame on an old house, but a healthy void does not smell.

A survey does not begin by lifting the floor. We prove a loss at the meter and, if the boiler is involved, at the pressure gauge. A thermal imaging camera scanned from above shows the line of a warm pipe through the boards and any cold, wet area spreading from it. A borescope camera goes through a hole the size of a pound coin, or through an air brick. It shows the joists, the pipe and any standing water without disturbing anything. The acoustic microphone and tracer gas narrow the point further where the void is deep or cluttered.

Once the leak is pinned to one place, one board is lifted and the pipe is exposed. The repair is made in copper or barrier pipe if you want it done on the visit. The board goes back and the report records what was seen, the readings taken and photographs of the pipe before and after. Where water has damaged joists, boards or plaster, that report supports a trace and access claim on your buildings insurance. Trace and access pays for finding the leak and making good the opening. Fixing the pipe is usually not covered, so we keep the costs separate.