Why most roof leaks are misdiagnosed

Water is a patient traveller. It enters at one point, follows a batten, a screw thread, a joint or a fold, and only appears inside the building somewhere quite different. That is why a stain in a bedroom ceiling is rarely under the actual failure, and why simply coating the ceiling side of the problem changes nothing.

A correct waterproofing response starts on the roof, not on the ceiling. It begins with a proper look at the substrate, the flashings, the parapets and the drainage: under load if possible, on a rainy day if the client agrees. Only then does it move to specification and product.

First: parapet capping. Water sits on top of a parapet, finds a crack in the mortar bed, and runs down inside the cavity for metres before showing itself. A coating on the wall face does nothing about this.

Second: flashing details around penetrations: geyser stands, aerials, vent pipes, chimneys. These are almost always the entry point on older roofs, and almost always missed on a quick quote.

Third: lifted or slipped tiles on the weather side of the roof. A single displaced tile can feed a leak that appears three rooms away.

Diagnosis on a Williams & Co inspection means climbing the roof, photographing what we see, mapping the water path back from the stain, and writing it down. If we cannot explain the water path in one clear sentence, we have not diagnosed it yet.

That written diagnosis becomes the scope of the quote. It is why our quotes read differently to a quick one-page price on the back of an assumption.