One of the most frustrating things about roof leaks is that the point where water appears inside your home is rarely directly below the point where water enters the roof. Water that enters through a small gap in a flashing or a cracked tile travels along battens, rafters, and sarking, following the path of least resistance. It might travel several metres horizontally before it finds a gap in the ceiling to drip through.
This means that a water stain in the middle of your bedroom ceiling might be caused by a problem at the edge of the roof, near a chimney, or at a completely different part of the roof structure. Diagnosing the source requires systematic investigation - both from inside the roof cavity and from the outside of the roof.
This is the number one cause of roof leaks on tile roofs in Canberra. The mortar pointing that seals ridge caps cracks and fails due to freeze-thaw cycles, thermal movement, and age. Once cracks appear, every rainfall sends water into the roof cavity.
How to identify: From the ground, look for visible gaps or missing chunks of mortar along the ridge line and hip lines. From inside the roof cavity, look for water staining on the underside of the ridge beam or top of the ceiling batts directly below the ridge.
Fix: Remove old mortar, re-bed ridge caps with flexible bedding compound, and re-point with flexible pointing. This is a permanent repair that addresses the root cause.
Tiles can crack from hail impact, foot traffic, falling branches, or long-term freeze-thaw degradation. Displaced tiles - those that have shifted out of position - create gaps where wind-driven rain can enter.
How to identify: A visual inspection from the ground can reveal obviously broken or shifted tiles. Binoculars help. From inside the roof cavity, look for localised wet patches or daylight visible through the tile layer.
Fix: Replace broken tiles with matching profiles and re-secure displaced tiles with clips. A straightforward repair when caught early.
Flashings seal the junctions between the roof and walls, chimneys, skylights, vent pipes, and where different roof planes meet. They are made of metal (usually lead, zinc, or Colorbond) and rely on sealant to maintain a watertight bond. Over time, sealant dries out and fails, metal corrodes, and building movement opens gaps.
How to identify: Look for lifted or corroded metal at wall-to-roof junctions. Inside the cavity, look for water staining near where the roof meets a vertical surface.
Fix: Re-seal with appropriate sealant, re-dress lead flashings, or replace corroded flashings entirely. The method depends on the type and condition of the existing flashing.
Valleys collect water from two roof planes and channel it downward. When the valley flashing corrodes or debris creates a dam, water is forced sideways under the adjacent tiles.
How to identify: If leaks appear along a line corresponding to where two roof planes meet, valley issues are a strong possibility. From outside, check for debris accumulation in valleys.
Fix: Clear all debris, and replace corroded valley flashings. Ensure tiles overlap valley flashings adequately on both sides.
Metal roof fixings have rubber washers that seal the screw hole against water entry. When these washers deteriorate (typically from UV exposure over 15 to 20 years), the seal fails and every screw becomes a potential leak point. Loose screws that have backed out due to thermal movement are also a common issue.
How to identify: From inside the roof cavity, look for drip marks at screw locations. On the roof surface, look for screws that sit proud of the sheeting rather than sitting flush.
Fix: Replace deteriorated rubber washers (or the entire screw assembly) and re-tighten any loose fixings. On older roofs, a systematic check and replacement of all fixings is recommended.
Skylights are among the most common leak sources because they create a large penetration in the roof surface with multiple sealing points. The flashing apron around the skylight, the seal between the flashing and the glass or dome, and the junction between the flashing and the roof material are all potential failure points.
How to identify: Water appearing around the skylight frame, drips from the skylight edge, or staining on the ceiling around the skylight.
Fix: Re-seal the skylight flashings, replace degraded rubber gaskets, or in severe cases, replace the skylight and its flashing kit entirely.
In an emergency - such as an active leak during a storm - temporary measures can minimise damage while you wait for a professional repair. These include placing a bucket under the drip, using towels to absorb water and protect flooring, and if safely accessible, placing a tarpaulin over the affected area on the roof. However, these are strictly temporary. No amount of silicone, roof sealant, or duct tape applied from the outside constitutes a permanent repair. Proper leak repair requires identifying the root cause and addressing it with appropriate materials and methods.
If you cannot identify the leak source from inside the roof cavity, if the leak involves flashings or structural elements, or if you are not comfortable working at height, call a professional. Our $99 roof inspection includes a thorough leak investigation with a detailed report identifying the source and recommended repair approach. Call (02) 5133 5608 or book online. We cover all ACT suburbs, 7 days a week.
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Tile roofs are the most common roof type across Canberra's established suburbs. Here is a detailed guide to the most common causes of tile roof leaks and how each one is repaired.
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