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Clay tile roof wear & damage:
In photographs & text this article describes & explains the causes of all types of wear and damage that can be found on clay tile roofs by visual inspection. These include roofing tiles that are cracked, broken, pitting, spalled, loose, or missing, and of course, leaks in a clay tile roof.
This article series explains clay tile roofing types, clay roofing tile inspection, tile roofing diagnosis, & tile roof repair.
Examples of Clay Tile Roof Wear or Installation Problems that Limit Roof Life
In discussing types of clay tile roof damage, we include advice about how to inspect a tile roof and on how, if ever, you might walk on a clay tile or concrete tile roof.
[Click any image for an enlarged, detailed version.]
Our page top photo shows clay roofing tiles installed in the Northeastern U.S. This roof had been damaged by foot traffic. Clay tile roofs are often damaged by foot traffic, ice and snow, or by severe storms.
Our photo (left) shows the author (DF, back to camera) examining a clay tile roof installed on the Hwang Lim Won orphanage in Seoul, Korea in 1966.
The roof was constructed using an S-tile profile and was not leaking. Tiles on the structure had to withstand Korean monsoon weather of heavy rain and high winds.
Our photo of a tarred roof valley and damaged interlocking clay roof tiles (above left) was taken from a ladder at roof edge. At above right, on a barn on the Roosevelt Estate in Hyde Park NY, ice and storm damage have broken many of these rectangular flat roof tiles.
[Click to enlarge any image]
The common failures on clay tile roofs include cracked broken tiles, spalling (in freezing climates), loose tiles that slide down out of place (on roofs where not every tile is secured to the roof deck), flashing failures (corrosion or cracking), and fastener failures. We also find leaks in clay tile roofs that were improperly flashed or that were built on a low slope and without a waterproof membrane.
Our photo of broken clay roof shingle-tiles (above right) was taken during an inspection made without walking on the roof surface - for obvious reasons: we didn't want to shoulder the blame for this damage.
The clay tile roof shown at left, located near Xotolar, Guanajuato, Mexico, is more than 40 years old and shows only minor damage.
We recommend against walking on clay tile roofs as you are likely to damage the roof leading to the need for costly repairs. More discussion on walking on fragile roofs is later in this article.
Our photo (above left) shows broken clay roof tiles, a very common clay tile roof defect that is also a common leak source.
At the photo lower left corner you can see a pair of replacement clay tiles that have been put in place, but more replacements are needed wherever a broken roof tile is found. Carson Dunlop's sketch (above right) illustrates the most common locations where cracked or broken tiles are found on clay tile roofs.
In some climates clay tiles may also become damaged by spalling from freezing when the tiles were wet.
When it is necessary to walk
on tiles, some authorities suggeest that you step only on the head-lap (lower 3 inches) of each
tile. With Mission- or S-tiles, it is best to step across two
tiles at once to distribute the weight. When significant
rooftop work is required, place plywood over the tile to
distribute the load.
Removal of Roof Tiles May Be Necessary for On-Roof Access
Watch out: our own experience is that it is absolutely impossible to walk on many clay tile roofs without damaging them, particularly soft clay such as the roof type used in Latin America (our photo at left).
For these roofs contractors have to remove sufficient clay tiles to provide a walking area. The removed tiles are replaced as the worker is leaving the work area of the roof.
On some other fragile but not totally fragile roofs such as slate roofs, cement tile, cement-asbestos, fiber cement, and hard-fired ceramic clay tile roofs, contractors suspend a ladder over the roof surface, hanging it from the ridge, and cushioning it off of the roof surface using foam or insulation padding, or contractors work from scaffolding. - Ed.
White Stains on Clay Tile Roofs
White stains on tile roofs are typically an efflorescence deposit and may indicate that the tile is absorbing water, thus nearing end of life. But the extent of effloresence and its significance in clay tile roofing varies quite a bit depending on the type of roofing tile (its degree of vitrification), climate, and other features.
Generally where we have seen white effloresence staining on clay tile roofs (such as the Mexican clay tile roof photographed below left ) I have not seen a notable correlation with remaining clay tile roof life.
The amount of water absorption into clay roofing tiles depends on the extent of clay vitrification, in turn an effect of how the clay tiles were fired or produced. Soft low-vitrification clay tiles such as those shown at above left (Mexico) are more likely to absorb water and would not perform well in freezing climates.
More often we see dark stains on these clay tile roofs, typically an algae formation. Generally low-vitrified soft clay tile roofs fail due to the fragility of the roofing tiles themselves, not from water absorption and mineral salt formation.
[Click any image for an enlarged, detailed version]
Our second clay tile roof (above right and in close-up at left), also showing some white effloresence stains on some tiles, is located in Duluth Minnesota. This roof is on an older home, is performing well in a very cold climate. This roof is almost certainly using a highly-vitrified clay roofing tile.
Other clay tile roofs I observed in Duluth and similar roofs I inspected in Oslo and Molde, Norway, used a vitrified flat clay tile that was also coated with a hard glaze. No white effloresence staining is found in these roofs.
Clay tile roofs are more likely to fail due to the fragility of the roofing tiles themselves, not from water absorption and mineral salt formation.
Hidden Structural Damage Below Clay Roofing Tiles
Here we illustrate another reason to stay off of clay tile roofs - very fragile, loose clay tiles and rotted collapsing structure below.
Walking on the roof we show at left is almost certainly going to break tiles and risk injury as the supporting structure may break below the inspector.
This particular roof condition could also be observed from inside the home's attic.
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black stains on clay roof
(Feb 20, 2013) Vinehoward@gmail.com said:
Purchasing a home and the Clay roof is blackened all over with what might be mold, or is it deterioration of the clay tile itself. Can it be cleaned and restored, and is a sealant needed to prevent future black staining?
Howard, typically the black stains on clay roof tiles are a species of algae. For diagnosis, remedy, and prevention of black stains on roofs see these articles:
Questions & answers or comments about wear & damage to clay tile roofs: spalling, pitting, cracking, breaking, loose, or missing clay tiles.
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Roof Tiling & Slating, a Practical Guide, Kevin Taylor, Crowood Press (2008), ISBN 978-1847970237, If you have never fixed a roof tile or slate before but have wondered how to go about repairing or replacing them, then this is the book for you. Many of the technical books about roof tiling and slating are rather vague and conveniently ignore some of the trickier problems and how they can be resolved. In Roof Tiling and Slating, the author rejects this cautious approach. Kevin Taylor uses both his extensive knowledge of the trade and his ability to explain the subject in easily understandable terms, to demonstrate how to carry out the work safely to a high standard, using tried and tested methods.
This clay roof tile guide considers the various types of tiles, slates, and roofing materials on the market as well as their uses, how to estimate the required quantities, and where to buy them. It also discusses how to check and assess a roof and how to identify and rectify problems; describes how to efficiently "set out" roofs from small, simple jobs to larger and more complicated projects, thus making the work quicker, simpler, and neater; examines the correct and the incorrect ways of installing background materials such as underlay, battens, and valley liners; explains how to install interlocking tiles, plain tiles, and artificial and natural slates; covers both modern and traditional methods and skills, including cutting materials by hand without the assistance of power tools; and provides invaluable guidance on repairs and maintenance issues, and highlights common mistakes and how they can be avoided.
The author, Kevin Taylor, works for the National Federation of Roofing Contractors as a technical manager presenting technical advice and providing education and training for young roofers.
The Carson Dunlop home study course for home inspectors can be examined at the company's website at http://www.carsondunlop.com/us/home-inspection-training/
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