Beyond the Surface
What Makes a Tile Roof Perform
by Richard K. Olson, President & Technical Director, Tile Roofing Industry Alliance
(Editor’s Note: Richard K. Olson is president and technical director for the Tile Roofing Industry Alliance. The association represents industry professionals involved in the manufacturing and installation of concrete and clay tile roofs in the United States and Canada, and works with national, state, and local building officials to develop installation techniques, codes, and standards for better roofing systems. Olson can be reached at rolson@tileroofing.org.)
Clay and concrete tile offer the longest service life of any steep-slope roofing material, and an unusually broad design palette to go with it. Profile, color, texture, and shadow can reinforce almost any architectural language, from traditional Mediterranean forms to contemporary western residences. Yet the tile is only the visible part of the roof.
Long-term performance depends on the complete assembly beneath and around it: deck, underlayment, flashings, attachment, drainage, ventilation, and transitions. It also depends on whether the roof geometry gives those components a reasonable job to perform. Decisions made while the roof plan is being developed influence how water moves, where debris accumulates, how penetrations are flashed, and whether critical details can be constructed as drawn.
Why the Expectations Are Higher for a 50-Year Roof
Asphalt shingles are replaced on a cycle that, without anyone intending it, forgives a lot of design shortcuts. A valley sized too small, a penetration placed in the wrong spot, a flashing detail that never quite worked, on a product with a 20-30 year lifespan, those get torn off and redone before the full cost of the original decision ever comes due. Concrete and clay tile does not offer that reset. At a service life of 50 years or more, whatever is built into the assembly at the design stage tends to stay there, working or not, for longer than most owners will hold the property.
That is not an argument against tile. It is the argument for it, and for treating its design with the same attention its performance deserves. A roof still protecting the building in 2076 earns the extra hour spent tracing water paths and coordinating valley details during design. A product that will be torn off and replaced twice more before then does not carry the same weight, which is exactly why a shortcut on a shingle roof is so much more forgivable than the same shortcut on tile.
Begin With the Roof Geometry
Roof geometry is often developed primarily as an expression of massing and style. Every added plane, however, changes the way the roof collects and directs water. Valleys receive runoff from multiple surfaces. Dormers create roof-to-wall intersections. Chimneys and wide penetrations interrupt natural drainage. Intersecting ridges can produce short, difficult transitions.
During design, trace the water path from every ridge to its point of discharge. Identify the roof area contributing to each valley, cricket, gutter, and downspout. Look for locations where water changes direction, becomes concentrated, or encounters a vertical surface. This often reveals opportunities to simplify the geometry or identify locations that deserve enlarged details and closer coordination.
Treat Underlayment as a Designed Component
Tile is the primary water-shedding surface, and a durable one. Underlayment is the secondary barrier behind it, as the layer that must perform if wind-driven rain, roof damage, or ordinary weather conditions allow water to get past the covering. That makes it an essential part of the assembly, not a generic layer selected at the end of the specification.
The appropriate system depends on roof slope, climate, deck type, ventilation configuration, expected construction exposure, and the requirements of the applicable code and tile manufacturer. Lower-slope applications may require different treatment than steeper roofs, while hot and freeze-thaw climates place different demands on materials. The design documents should establish the required performance and coordinate the underlayment with the covering, deck, insulation, and ventilation strategy.
Design the Water Path at Valleys & Transitions
Valleys and transitions concentrate water and bring multiple materials together. They should be designed as part of one continuous drainage path rather than treated as isolated standard details. Key decisions include:
• Valley capacity: relate flashing configuration and width to roof area, slope, tile profile, expected flow, and debris exposure.
• Underlayment continuity: show how underlayment interfaces with valley metal, eaves, walls, penetrations, and changes in slope, including required overlaps and material specifications.
• Flashing geometry: direct water back onto the roof surface or into defined drainage without relying on sealant to correct incomplete flashing.
• Crickets and saddles: size them for the width of the obstruction and carry water far enough away from vulnerable sidewalls.
• Discharge points: confirm that upper roofs, scuppers, and downspouts release concentrated water onto a clear path, not directly onto sensitive transitions below.
These conditions should be coordinated before construction rather than improvised after the tile layout is underway. The applicable code, TRI installation guidance, and tile manufacturer instructions provide the technical baseline while project-specific drawings must show how that guidance applies to the roof being designed.
Coordinate Everything That Shares the Roof
The roof is rarely occupied by roofing alone. Plumbing vents, mechanical equipment, skylights, attic vents, satellite equipment, and photovoltaic systems all compete for space. When they are placed independently, the consequences are often transferred to the roofing contractor. Penetrations may land in valleys, too close to hips, or beneath concentrated drainage. Equipment can block access to flashings, and later installations may require tile to be removed and reinstalled.
A coordinated roof plan should keep penetrations away from concentrated drainage where practical, group compatible penetrations, preserve working space around curbs and walls, coordinate photovoltaic attachment and flashing requirements, and maintain access for inspection and future repair. Moving a penetration on paper is far easier than rebuilding a valley in the field.
Translate Design Intent Into Buildable Details
A specification may correctly reference the governing code, approved installation guide, and manufacturer instructions, but general references do not replace project-specific details.
The drawings should communicate unusual conditions, material transitions, and locations where a standard detail does not fit. Enlarged plans and sections are especially valuable at intersecting valleys, low-slope transitions, parapets, curved walls, and changes in tile profile.
Tile layout should also be considered. Small cuts at hips, valleys, and penetrations can be difficult to secure and may undermine the appearance the architect intended. Minor dimensional adjustments during design can produce a cleaner module and more reliable installation.
Attachment requirements must reflect location, roof height, slope, exposure, applicable wind design, the selected tile, and manufacturer instructions. An approach appropriate for one building should not be carried into another without reviewing those variables. Preinstallation coordination among the architect, roofing contractor, manufacturer or supplier, and affected trades can resolve these questions before materials reach the roof.
Protect the Assembly After Installation
Good design can still be compromised after the roofing contractor leaves. Solar installers, mechanical technicians, painters, and other trades may walk on tile without appropriate training or remove units without restoring the original attachment and flashing. Future penetrations should be treated as modifications to several coordinated layers of the building envelope, not merely as holes through tile.
One point is worth adding here: a roof designed well and inspected poorly can still fail, but a roof designed poorly cannot be rescued by any inspection schedule. The design decisions described above are what a proper maintenance program has to work with.
Performance Is the Result of Coordination
Concrete and clay tile can provide enduring architectural character, but performance is not created by appearance alone. It results from coordinated decisions made from the roof plan through project closeout. The architect establishes the geometry. The specifications define the assembly. Manufacturers provide product requirements. Contractors translate the documents into a functioning roof. Owners preserve that performance through appropriate access, inspection, and maintenance.
When those responsibilities are connected, tile does more than finish the building. It becomes part of a complete steep-slope roof assembly designed to manage water, accommodate movement, support future work, and protect the structure over the long term.
Beyond the surface, that coordination is what makes a tile roof perform longer than any other roof option. For design professionals and contractors seeking more information about concrete and clay roofing applications, Tile Roofing Industry Alliance installation resources, or certified contractors, visit www.tileroofing.org.
