Clay tile roof flashing leaks:
This article describes common leak points in flashing on clay tile roofs.
We explain the conflict between stopgap leak patching using asphalt-based roofing cement and the corrosive effect that leads to additional deterioration of metal roof flashings. This article series explains clay tile roofing types, clay roofing tile inspection, tile roofing diagnosis, & tile roof repair.
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On modern clay tile roofs, especially where curved mission style tiles are installed, the flashing material is often custom built of copper, lead coated copper, or hand-made using soft copper; traditional clay tile roofs.
Especially where flashing material needs to rest atop curved clay roofing tiles, factory-built or site-built curved soft-metal flashing or flexible membrane self-adhering membranes are most widely used.
Some contemporary tile roof installations use lead sheets that were easily formed to follow the contour of the clay tiles, but modern flashing products include metal that is pre-formed to match tile shapes.
The flat clay tile roof shown at above left, located in Poughkeepsie, New York, demonstrates traditional copper flashing visible at the intersection of the roof tiles and the dormer face.
Flashing at the dormer sides is not exposed but we expect that conventional step flashing was installed under those tiles, possibly with a counter flashing, also not visible. In an un-finished attic one can often spot the nails that secured the roof flashing to the dormer sheathing and roof deck in these locations.
Our second clay tile roof flashing photo (above right) illustrates copper valley flashing, also on a home in Poughkeepsie, NY. Below the clay tile roof valley has been patched as have two damaged roofing tiles. This is a reasonable stop-gap roof repair but not a durable one.
In fact inspecting several copper-flashed older roofs that were being disassembled for renovations we found compelling evidence of the down-side of blobbing asphalt based roofing cement or flashing compounds on metal roof flashing.
The roof flashing was literally corroded away more extensively wherever it had remained in long-term contact with the flashing cement. So while the patch job stopped the initial leak, it also ultimately corroded away the flashing material.
Our two photos below illustrate leaks at roof-cement patch jobs on a clay tile roof.
The short term reliability of roof cement to fix leaks is illustrated by these photos.
Differences in materials and intense thermal movement in a clay tile roof, combined with dry-out and shrinkage in the asphalt roof cement used to patch the tile roof shown at above left meant a history of recurrent leaks in this roof (photo above right).
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