What causes roof leaks in Sydney homes?

Blocked or corroded valleys

The valley is the metal channel where two roof planes meet, and it carries more water than any other part of the roof. Leaf litter collects there, holds moisture against the metal, and eventually rusts a pinhole or a whole section through.

A valley leak typically shows up during sustained heavy rain rather than a light shower, and often stains a ceiling some distance from the actual fault because water runs along a batten before dropping.

Failed ridge capping and pointing

Traditional cement pointing goes hard, then cracks as the roof moves and heats. Once it cracks, wind-driven rain gets under the capping and into the roof space. In Sydney this is one of the most common leak sources on tile roofs over about 20 years old.

Flashings that were never right

Chimneys, parapets, skylights, wall abutments and vent penetrations all rely on flashing. Where a flashing was surface-sealed rather than properly turned into the brickwork, it will leak eventually — often years later when the sealant perishes.

Gutters that overflow backwards

A gutter that is blocked, sagging or has lost its fall backs water up under the roof edge and into the eaves. Owners often assume this is a roof leak; it is a drainage problem, and the fix is different.

Low-pitch additions

Rear additions and enclosed verandahs are frequently built at a pitch below the minimum for the roofing material used. They cope in ordinary rain and fail in a heavy downpour, because water moves too slowly to clear the laps.

What to note before you call

• Which rooms and which part of the ceiling
• Whether it happens in all rain or only heavy, wind-driven rain
• Whether it started after a storm or has been getting slowly worse
• Any recent work — solar panels, antennas, additions, painting