Why Tiled Roofs Leak: The 8 Usual Causes and How Each Is Fixed

Causes 1 and 2: cracked and slipped tiles

1. Cracked tiles. Concrete and terracotta tiles crack from hail, from branches, from age and most often from people walking on them the wrong way. A crack in a tile lets water straight through to the sarking or, on older roofs with no sarking, straight into the ceiling. On the Sunshine Coast, hail is a regular cause: the 2025 season produced stones of 8 to 14 cm across the south-east, which crack even sound tiles.

2. Slipped or lifted tiles. Tiles hook over battens and are held by their own weight and, on the edges and ridges, by clips. When a clip corrodes or a batten sags, a tile slides down and opens a gap above it. Wind can also lift tiles that are not fixed, which is why AS 2050:2018 covers mechanical fixing.

The fix: replace the cracked tile with a matching one and re-seat or clip the slipped one. The whatsthedamage Sunshine Coast guide lists a tile replacement job at $290 to $970, with $580 typical, and ABC Roof Restoration starts at $50 per tile. Matching an old tile profile is part of the work, and our tiled roofing team handles it.

Causes 3 and 4: ridge mortar and pointing

3. Cracked or missing pointing. The thin finishing layer along every ridge and hip is the first thing to fail on a tiled roof. Mortar is rigid, the roof moves, and ridge mortar is expected to crack within 8 to 15 years. Once it cracks, wind-driven rain runs under the caps.

4. Failed bedding. Under the pointing sits the mortar bed that holds the caps. When water has been getting into it for a few seasons the bed crumbles, the caps rock, and the gaps get bigger every storm. Leaks from failed bedding show up as stains along a hip line or near the top of a room.

The fix: re-pointing with a flexible compound where the bed is sound, or lifting the caps and re-bedding where it is not. The same Sunshine Coast guide lists a ridge capping repair at $390 to $1,175, and Rite Price Roofing puts full re-bedding at $40 to $80 per metre. We explain the difference in our ridge capping guide, and the service is on our ridge capping and re-pointing page.

Causes 5 and 6: valley irons and flashings

5. Rusted valley irons. A valley is the metal channel where two roof faces meet at an internal angle. It carries more water than any other part of the roof and holds leaves, so it stays wet. On the Sunshine Coast, salt finishes the job. The AS 4312 corrosivity guide puts anything within 200 m of a surf beach in the harshest C5 band, and valleys on beachfront homes at Buddina and Sunshine Beach rust through well before the tiles show any wear. A rusted valley leaks under the tiles where nobody sees it.

6. Failed flashings. Flashings seal the joins around chimneys, vent pipes, skylights and where a roof meets a wall. They lift as the sealant ages, corrode near the coast, and get disturbed when aerials or solar cabling go in. A lifted flashing leaks every time it rains, right at the spot it protects.

The fix: a rusted valley iron is cut out and replaced; tiles either side are lifted and reset. Flashings are re-fixed and re-sealed, or replaced where corroded. Both are standard roof repairs. Our guide on salt air and your roof explains why coastal valleys go first.

Causes 7 and 8: blocked gutters and low pitch

7. Blocked gutters and valleys. When a gutter cannot drain, water rises over its back edge and runs into the eaves and the wall cavity. When a valley is full of leaves, water spreads sideways under the tiles on both sides. In a heavy fall this happens fast. The Bureau of Meteorology records 217.5 mm of rain in an average February at Sunshine Coast Airport, and a good part of that comes in single storms.

8. Low pitch and missing sarking. Tiles shed water by gravity and overlap. AS 2050:2018 sets a minimum pitch of 15 degrees for roof tiles. Below that, wind pushes rain back up under the laps. Sarking is the reflective membrane under the tiles that catches that water and drains it to the gutter, and older roofs often have none, or have sarking that has torn at the eaves.

The fix: clear the gutters and valleys, and check the fall and the downpipes. For a flat section that keeps leaking, options range from sarking under the tiles during a re-tile to changing that section to metal. See gutter and fascia painting for keeping gutters sound, and our storm season checklist for what to clear before the wet.

Finding where the leak is coming from

A stain on the ceiling is rarely under the hole in the roof. Water gets past a tile, lands on the sarking or a batten, runs downhill along it and drops off somewhere else. On a roof with a steep pitch that can be several metres from the source. So we work backwards from the stain, uphill along the rafters, and check every ridge, valley, flashing and tile above it.

A few patterns help narrow it down:

• Leaks only in wind-driven rain point to ridges, pointing, low pitch or a lifted flashing.
• Leaks in every fall point to a cracked tile, a rusted valley or a blocked gutter.
• Stains along a hip or the top of a wall point to bedding and pointing.
• Stains around a light fitting or vent point to the flashing above it.
• Damp at the eaves or a wet outside wall point to gutter overflow.

We do this on every roof leak repair, and we do not stop at the first fault. Many leaking roofs have more than one fault, and fixing a tile while a valley is rusting through only moves the problem. Published Sunshine Coast guides list a roof inspection at $195 to $485.

Repair or restore?

A single cause gets a single repair. Published Sunshine Coast guides list a minor leak repair at $240 low, $485 typical and $775 high, and Canstar puts a spot repair at $200 to $500. Those are guide figures. A cracked tile, a lifted flashing or a short run of pointing sits in that range.

When the list is long, the sums change. If the ridges need re-bedding, several valleys need replacing and the tiles have gone chalky and porous, you are paying for most of a restoration without the coating that would stop the next round. A full roof restoration does all the repairs in one go, then seals the surface under a primer and two membrane coats with our 10-year warranty (terms apply). The cost calculator gives you a starting range for that.

Either way, start with a look. We estimate from satellite imagery, then inspect on site. We work across the coast, from Pelican Waters and Mountain Creek to Bli Bli and Noosaville. If water is coming in now, contact us and we will get to it.

Sources

• ABC News on south-east Queensland hailstorm frequency, 2025
• AS 2050:2018 Installation of roof tiles
• whatsthedamage roofing cost guide, Sunshine Coast
• ABC Roof Restoration cost guide
• Roofing Calculator HQ ridge cap cost calculator
• Rite Price Roofing re-bedding and re-pointing cost
• GAA corrosivity environment guide, AS 4312
• Bureau of Meteorology, Sunshine Coast Airport climate averages

Tyler Czebotar, Seaspray RestosQBCC licensed roof restorer on the Sunshine Coast, 15 years in roofing. About