Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
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 on Roofs for 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 slope, sheathing, underlayment specifications: this article describes the requirements & specifications for clay tile roof installation: roof slope, roof sheathing,m and clay tile roof underlayment.
This article series discusses best practices in the selection and installation of residential roofing. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.
Also see our clay roof tile home page CLAY TILE ROOFING and 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.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
Roof Slope Requirements for Tiled Roofs
Most manufacturers recommend minimum slope requirements for their tiles as well as special underlayment and fastening techniques for low-slope installations.
[Click to enlarge any image]
Typical minimums are shown in Table 2-5. Some manufacturers allow specific tile types to be installed on roofs as shallow as 2 1/2 :12 if a full waterproofing layer, such as a built-up roof or single-ply membrane, is installed.
Reduced exposure and special fastening techniques may also be required for low slopes.
On slopes less than 3 1/2 :12, roofing tile is considered decorative only. The underlying roof provides all the necessary waterproofing.
In general, there is no maximum slope for tile roofs. However, on extremely steep roofs above 19:12 or on vertical applications, wind currents may cause tiles to rattle. To avoid this, use wind clips on each tile along with a construction grade silicone sealant or other approved sealant.
More information about roof slope & roof slope calculation or measurement is at ROOF SLOPE DEFINITIONS.
Roof Sheathing Requirements for Tiled Roofs
While spaced sheathing is allowed under the codes, most installations today are done on solid wood sheathing with or without battens. The sheathing must be strong enough to support the required loads between rafters. Minimum requirements are nominal 1 inch for board sheathing or 15/32 for plywood and other approved panel products.
Underlayment Requirements for Clay Tiled Roofs
Because of the long service life of tile, a long-lasting underlayment should be used as well. Underlayments play a key role in tile roofing, since most tile roofs are not completely waterproof.
At a minimum, use a Type II No. 30 or No. 43 felt, lapped 2 inches on horizontal joints and 6 inches at end laps. The underlayment should lap over hips and ridges 12 inches in each direction and turn up vertical surfaces a minimum of 4 inches (Figure 2-20).
At tricky areas, such as around roof vents, chimneys, and skylights, self-adhesive bituminous membrane can help achieve a watertight seal.
In windy areas, use tin caps or round cap nails to hold the underlayment securely. The fastening schedule for the underlayment will depend on local wind conditions.
For harsher conditions or shallower slopes, use mineral surface roll roofing, self-adhering bituminous membrane, or other durable waterproofing systems.
For slopes below 3-1/2:12 the underlayment must provide complete weather protection, and the tiles are considered merely decorative. Underlayment recommendations for different types of tiles and climate conditions are shown in Table 2-6, Table 2-7, and Table 2-8 below. [Click to enlarge any tables or images in these articles.]
Tile Roof Underlayment Options from NRCA
In the 1990's NRCA's Thomas Smith noted that a paper published in the Proceedings of the 10th Conference on Roofing Technology expressed concern for the lack of conservative roofing industry guidelines for the components of tile roofing systems in the U.S.
The recommendations in the then-current NRCA Steep Roofing and Waterproofing Manual indeed included recommendations for tile roof underlayment, fasteners, and metal flashings, but Smith noted that these were "non-conservative" for many areas in the United States (and other locations of challenging weather). Smith posed some interim underlayment options to improve the life of tile roof systems, including for 4" in 12" or greater (steeper) sloped tile roofs:
Special provisions were needed for lower slope roofs (under 4" in 12")
Roofing Materials, Methods, Standards
Where to Buy Clay Roof Tiles
-- Adapted with permission from Best Practices Guide to Residential Construction.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs) about clay tile roof slopes & requirement for underlayment
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 slope, sheathing, underlayment specifications.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References