Our page top photo shows clay roofing tiles installed on a low slope roof in San Miguel de Allende, Mexico. Below we comment on the special steps needed to keep a low slope clay tile roof from leaking.
The installation guidelines for clay roofing tiles vary widely by geographic area. For example at How clay roofing tiles are secured we include a photograph of a clay tile roof in a mountainous area of Mexico where very little is done to fasten the tiles to the roof structure.
Our photo at left shows a tile roof ready for installation in Mesquite Cove, Arizona. The tiles will be secured to battens nailed over an underlayment. Notice the drainage gaps in the batten strips.
In windy or stormy areas owners sometimes leave heavy stones on the edges of their roof to avoid wind blow-off of the tiles. In coastal areas where high winds and hurricanes are a threat to all roofs, extra steps are taken to fasten tiles to the roof surface.
Clay tile roofing material and installation labor are more expensive than alternate materials, but the material has a life expectancy of up to 350 years where high quality vitreous tiles are used. Clay tiles are heavy, weighing between 850 and 1,700 pounds per square (depending on the tile type).
Roof Slope or Pitch Requirements for Clay Tiles
Clay roofing tiles are installed on slopes as low as 4/12, restricted to 6/12 in some jurisdictions. Our photo (above left) shows a low slope clay tile roof in San Miguel de Allende, Mexico.
This roof was built without sufficient pitch (about 2/12) and it leaks badly during heavy rains, as you can see by our photograph of the roof's under-side (above right). Raising the high end of this shed roof a few inches will improve the roof drainage and stop the leak problem.
Where clay tiles are installed on low slope roofs (less than 4/12) for aesthetic reasons, install a waterproof membrane on the roof surface below the tiles.
The clay tile roof support system shown at left uses locally-cut trees and bamboo-like grasses to support the roofing tiles. This system works acceptably in areas such as central Guanajuato, Mexico where the structure is not subjected to high winds nor freezing weather.
Even here, a too-low-slope clay tile roof will be quite leaky - which is of little concern if sheltering only an outdoor shed or animals in a warm climate.
Most clay tile roofs permit exposure of more than 50% of the length of the tiles, and interlocking clay tiles have an 80% to 90% exposure of the tile surface. An exception is that for shingle flat clay roofing tiles the exposure is less than 50%.
Head lap specification for clay tile roofs
Interlocking and curved clay roof tiles have no head lap. Clay roof shingle tiles have a 2" to 4" head lap.
Photo above: clay tile roof installation in Boca Raton, Florida.
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Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. Mr. Cramer serves on the ASHI Home Inspection Standards. Contact Mark Cramer at: 727-595-4211 mark@BestTampaInspector.com
John Cranor is an ASHI member and a home inspector (The House Whisperer) is located in Glen Allen, VA 23060. He is also a contributor to InspectApedia.com in several technical areas such as plumbing and appliances (dryer vents). Contact Mr. Cranor at 804-747-7747 or by Email: email@example.com
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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.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
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Green Roof Plants: A Resource and Planting Guide, Edmund C. Snodgrass, Lucie L. Snodgrass, Timber Press, Incorporated, 2006, ISBN-10: 0881927872, ISBN-13: 978-0881927870. The text covers moisture needs, heat tolerance, hardiness, bloom color, foliage characteristics, and height of 350 species and cultivars.
Slate Roofs, National Slate Association, 1926, reprinted 1977
by Vermont Structural Slate Co., Inc., Fair Haven, VT 05743, 802-265-4933/34. (We recommend this book if you can find it. It
has gone in and out of print on occasion.)
The Slate Roof Bible, Joseph Jenkins, www.jenkinsslate.com,
143 Forest Lane, PO Box 607, Grove City, PA 16127 - 866-641-7141 (We recommend this book).