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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 roofs: This article explains clay tile roofing types, clay roofing tile inspection, tile roofing diagnosis, & tile roof repair. Our page top photo shows clay roofing tiles installed in Patzcuaro, Mexico. Clay roofing tiles have been used in Europe, the Middle East, and Asia, since the Greek and Roman Empires, and the Americas since Europeans arrived there.
Clay tile roofing material is costly to purchase and install, but it can have an indefinite life expectancy.
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The clay roof tile systems we discuss in this article series are "real" clay tile roofs on which the tiles themselves are intended to provide the water shedding and drainage necessary to form a dry covering over a building.
At left the very damaged clay tile roof depended on the tiles themselves to carry away rainfall. But other roofs use clay tiles to protect a waterproof underlayment from sun and for aesthetic reasons.
Such "cosmetic" clay tile roofs are commonly installed in some areas (Boca Raton, Florida) over a completely functional waterproof membrane.
Cosmetic clay tile roofs also protect the roof membrane from deterioration from sunlight, but the tiles themselves are not forming the waterproof covering.
A Little History of Clay Roofing Tiles in the U.S & Other Countries
Our photo (left, by the author DF- 1966) shows decorative clay roofing on Yongnyong-jon hall, a Korean shrine forming part of the oldest shrine in Korea Jeongjeon, the Jongmyo Confucian shrine constructedby King Jaejo beginning in 1394.
Koreans believed that the royal spirits achieved peace only after their tablets were brought here from Chongjon. Thus, Chongjon enshrined the souls still roaming the earth, while Yongnyong held those who had achieved eternal rest.
As NPS historic preservation expert Sweetser points out,
Our glazed roof tiles shown below were on homes in freezing climates of Norway (below left) and Duluth, MN (below right). Best Practices Guide to Residential Construction points out that
Photo above left: highly vitrified glazed clay tile roof in Molde, Norway. At abovbe right, a vitrified clay glazed flat tile roof in Duluth, Minnesota. Both of these roofs tolerate freezing climate and other harsh weather conditions.
[Click to enlarge any image]
Clay roof tiles, typically 7" x 13" are 1/4" to 1/2" in thickness and are shaped in molds and fired in a kiln to 2000 degF to cause the clay to vitrify. The vitrification (glasification) process makes the tiles hard and waterproof by melting and fusing silicas and aluminas in the clay.
Clay roofing tile surfaces may also be decorated with an embossed pattern to resemble wood, slate, or stone. Un-glazed tiles are terra-cotta red, a color provided by iron oxide in the clay.
Clay roof tiles may also be made with a colored glaze, adding both color and an additional layer of hard surface protection. While traditional clay tile glazing was performed by hand dipping and pouring glazing compound over the tiles, Carson Dunlop point out in their Home Study Course for home inspectors, since the 1970's glazing on clay tiles has been spray applied and the tile backs are left un-glazed, both reducing tile cost and permitting moisture to escape from the back surface of the tile.
In between the soft, fragile un-glazed low-fired clay tiles of Mexico and South America and the hard-fired glazed roofing tiles used in northern climates are harder-fired but unglazed clay roofing tiles we see in frequent use in Arizona where tolerance for sun makes these a long-lived material compared with lower-cost asphalt shingle roof coverings.
Both flat and curved clay tiles are in wide use in the American Southwest. The clay tile roof shown at above left is located near Phoenix, and at above right the clay tile roof is on a building located in Surprise, Arizona.
Higher quality clay roofing tiles are kiln fired to a higher temperature, are harder, less porous, and thus more durable. Inexpensive clay roofing tiles that are fired to lower temperatures insufficient to achieve vitrification are soft, easy to break, and less water resistant.
Carson Dunlop's sketch (left) illustrates the traditional tapered mission style clay roof tiles, and at right, the less-rounded barrel-mission style clay roof tiles. [Click to enlarge any image]
Carson Dunlop's sketch (left) illustrates the Spanish roofing tile that is roughly "S" shaped, including the pan or drainage trough on the left side of the tile and the raised tile surface on its right side. Variations of these interlocking tiles include a lower-profile "S" tile and also Greek and Roman clay roof tiles.
All of the rounded mission tile roofing materials need to be enclosed at the eaves or lower roof edge to avoid blowing rain and wind (wind-lift damage) and animal entry. Tile end closure is discussed at How clay roofing tiles are secured.
Our photo (left) and Carson Dunlop's sketch (above right) illustrate a typical interlocking roofing tile that is flat.
In our photo you can see metal tabs that mark the location of inserted replacement or repair clay tiles. The tabs should be bent up over the tile edges but appeared to have been flattened by snow sliding down the roof.
This clay tile roof was located near New York City. Lots of these tiles were broken, particularly on the low slope roof section: we suspected some of the clay tile roof damage was due to foot traffic.
See ROOF INSPECTION SAFETY & LIMITS where we provide more photographs of this roof (Walking on Clay Roofs) and This article explains roof safety and roof damage issues when inspecting, repairing, or otherwise walking on clay tiles as well as other roof materials such as asphalt, slate, and wood roofs.
We recommend against walking on clay tile roofs as you are likely to damage the roof leading to the need for costly repairs. 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. our photo of a tarred roof valley and damaged interlocking clay roof tiles (above left) was taken from a ladder at roof edge.
Details about clay roofing tile shapes, profiles, styles, types are at CLAY TILE ROOF STYLES, DESIGNS for detailed descriptions of different clay roof tile styles and characteristics, and at ROOFING TILE SHAPES & PROFILES where we discuss the basics of roof tile profiles and what they mean.
The illustrations of of how clay roof tiles are secured (below left) and of typical eaves closure of the open ends of Spanish or mission style roof tiles was provided courtesy of Carson Dunlop Associates. The tile roof eaves closure and drain openings shown below are on homes in Surprise, Arizona. Notice the larger drain opening in the eaves closure for the roof at below right. [Click to enlarge any image.]
Details about clay roofing tile fastening specifications are at CLAY TILE ROOF CONNECTIONS.
Photos below: at below left is a mission style clay tile roof with an open eaves design, Buenos Aires, Argentina. At below right is an open eaves clay tile roof design in Molde, Norway.
Clay tile roof eaves are also left open routinely in warmer climates such as Mexico, Central and South America, as we illustrate below with this roof from Xotolar, Guanajuato, Mexico.
Best Practices Guide to Residential Construction lists these producers and sources of clay roofing tilies, roof tile fastening systems, and related clay roofing products
Clay Roofing Tile Fasteners & Adhesives - Sources & Manufacturers
-- Adapted with permission from Best Practices Guide to Residential Construction.
As we discussed at SLATE ROOF INSPECTION & REPAIR, the fasteners or metal flashings on clay tile roofs are more likely to wear out than the tiles themselves. However clay tile roofs are often damaged by foot traffic, ice and snow, or by severe storms. Also see CLAY TILE ROOF STYLES, DESIGNS for detailed descriptions of different clay roof tile styles and characteristics, and see ROOFING TILE SHAPES & PROFILES for the basics of roof tile profiles and what they mean.
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Frequently Asked Questions (FAQs) about clay tile roofs
Question: What is the minimum slope for a tile roof?
(Feb 18, 2013) what is minimum roof degree requ said:
what is minimum roof degree require for clay roof tile
Reply: waterproof membrane required beneath roofs at slope under 3:12
About minimum slope allowed for clay tile roofs or other tile roofs, if you read through standards such as ICC-ES-ESR2015 "Concrete and Clay Roof Tile Installation Manual for Moderate Climates" (copy on file) you'll see that there is no prohibition of clay tiles on low slope roofs. Rather for slopes at 3:12 or less the installer is required to install a BUR or similar waterproof membrane on the roof below the tiles.
The document I cite is available from the Roofing Institute - the Western States Roofing Contractors Association (TRI/WSCRA) and other sources.
I give contact information for the Tile Roofing Institute in the article above,
Question: why do I see daylight through the tile roof? Does that mean it leaks?
(Jan 25, 2013) Anonymous said:
I am in process of Purchasing a home with spanish clay tile without underlayment. We checked for water leaks and surprisingly there are none but on a sunny day, we can see the light poking through the holes...How could that be? Can someone advise if it is safe to purchase it. There are [no] water stains either
5/2/2014 Rob said:
Hi anonymous, hopefully I can catch you. I am curious about what happened in your situation. I just found out that the home I really want to buy has the same problem with no underlayment (concrete tiles,not clay).
Rob and Anon,
On some roof designs, particularly if there is sufficiently steep slope, in the attic one might observe daylight filtering in through the roof covering for a slate or clay tile roof that is installed on spaced nailers. The roof may never leak, given pitch and adequate head lap of the slates or tiles, OR it may leak horribly if there is wind-driven rain blowing water up-slope.
In that circumtance on an older home the observation of leak stains on the nailers or on the floor below would be helpful clues telling us that the roof has or has not leaked.
"Safe to purchase" is too big and vague a question to answer by text with almost no information about a building.
Questions & answers or comments about clay tile roof installation, maintenance, inspection & repairs.
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