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ROOFING INSPECTION & REPAIR
AMERICAN CEMWOOD ROOFING
BEST ROOFING PRACTICES
BUILT UP ROOFS
CATHEDRAL CEILING VENTILATION
CERTIFICATIONS for ROOFING CONTRACTORS
CHIMNEY FLASHING Mistakes & Leaks
COLD WEATHER ROOF TROUBLE
DECKS, ROOFTOP CONSTRUCTION
EPDM, RUBBER, PVC ROOFING
EXTRACTIVE BLEEDING on SHINGLES
FIRE RETARDANT PLYWOOD
FLASHING on BUILDINGS
FLAT ROOF MOISTURE & CONDENSATION
Green House or Solarium Roof Leaks
HEAT TAPES & CABLES for ROOF ICE DAMS
ROOF ICE DAM LEAKS
MASONITE WOODRUF FIBERBOARD ROOFING
NOISE CONTROL for ROOFS
PLASTIC ROOFING TYPES
PVC, EPDM, RUBBER ROOFING
ROOF ARCHITECTURAL STYLES - PHOTO GUIDE
ROOF CLEANING RECOMMENDATIONS
ROOF COLOR RECOMMENDATIONS
ROOF INSPECTION SAFETY & LIMITS
ROOF LEAK DIAGNOSIS & REPAIR
ROOF NOISE TRANSMISSION
ROOF REPLACEMENT SNAFUs
ROOFING FELT UNDERLAYMENT REQUIREMENTS
ROOFING MATERIALS, Age, Types
SADDLE CONSTRUCTION at CHIMNEYS
SNOW GUARDS & SNOW BRAKES
STANDARDS for ROOFING
STRESS SKIN INSULATED PANELS
TEST LABS - ROOF SHINGLE
TREES & SHRUBS, TRIM OFF BUILDING
TRUSSES, Floor & Roof
UNDERLAYMENT REQUIREMENTS on ROOFS
VENTILATION in BUILDINGS
WALK-ON ROOF SURFACES
WARRANTIES for ROOF SHINGLES
WORKMANSHIP & ROOF DAMAGE
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.
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[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.
Foot Traffic Advice: Walking on Clay Tile Roofs
Profile tile and lightweight tile are the most vulnerable, and concrete tiles are more fragile when they are freshly manufactured or “green.”
If possible, place antennas and other roof-mounted equipment where it is easy to access without crossing many tiles.
Roof access hazards are discussed at ROOF INSPECTION SAFETY & LIMITS
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.
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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