There are many reasons that cause your roof to leak. Amongst them are a few reasons listed below.
Skylights: Some skylight installations leak the day they are cut into a roof. This is usually because of a poor selection of skylights or a faulty installation. The life of a skylight is usually less than the roof, so old rusty skylights leak and need replacement.
Broken roof tiles: Roof tiles often break if you have falling branches and overhanging trees.Children like throwing things and these things can break fragile roof tiles.There is a danger of broken tiles as soon as you let people walk on your tile roof.
Rusty valleys: Another reason for a roof that leaks is because of the rusty valleys. Although tile roofs do not rust, there are valleys on many roofs and in the old days, they just used galvanized metal valleys. These valleys have a 20 to 30 years life and rusted valleys are quite common on Sydney roofs.
Faulty tile ridge capping: The bedding under tile ridge capping crack with the passing time. Water seeps into the cracks and does three things.
It can pool behind the bedding and eventually overflow into the roof cavity.
It can run along the back of the bedding and find a drainage path along the tile and seep out without causing any harm.
It can run along the back of the bedding and not find a release drainage path.
The result is a leak. These leaks are hard to spot without removing the ridge capping first.
Chimneys: The flashings around chimneys deteriorate and often cause leaks.
Faulty flashings: The edges of roofs have to be waterproofed by flashings. If a new roof leaks, then the roofer usually has made a mistake on the roof flashing. We can usually evaluate the quality of the roof installation by evaluating the finishing off the flashes.
Rusty roofs: It is easy to see if a roof is rusty. Although it takes a while between when a roof begins to rust and when holes form and water starts dripping. Often the rusty areas are hidden but close inspection will reveal the rust spots at laps.