Many
regions within the U.S. experience wind conditions that are powerful
enough to damage homes, and given the roof’s location on the structure,
it can be very susceptible to loss; thus, the contractor’s role in
guiding homeowners in choosing appropriate roof materials in wind-prone
regions is essential. For homeowners in wind-prone areas, roofing
materials that can withstand severe wind events are indispensable.
Concrete roofing tile is an excellent option to defend against the
powerful forces of wind and reduce the chances of weather-related
property damage.
It is worth noting just how complex wind can be.
Not only is it directly affected by temperature and barometric pressure
differences in the atmosphere, but variations also influence it in
terrain and topography.
Despite these variables, wind acts in
relatively predictable ways once it impacts the surface of the home. For
example, when the wind hits the side of the structure, it travels
upwards and over the roof edge, resulting in varying degrees of uplift
pressure.
Wind Uplift Considerations
ASCE 7-22, or “Minimum Design Loads and Associated Criteria for Buildings and Other Structures1,” is an integral part of U.S. building codes. It outlines wind uplift pressure considerations, with the key points being:
- The
uplift pressures that affect a roof are highest at the corners of the
roof (i.e., eave/rake corner, peak of the ridge at the rake edge). - The edges: rakes and eaves, are a close second in uplift pressures.
- As
wind moves across a roof’s surface, negative pressure, or suction, is
created and results in an uplift toward the centers of a roof plain.
Some concrete roof tile applications have been tested to perform in sustained wind speeds up to 180 miles per hour when installed according to industry and manufacturer guidelines.
What impacts How Wind Affects the Roof
Many
factors influence how the wind may affect a roof it meets. These
include both speed and direction. Additional factors include:
- The Design of the Roof: Steep-pitched, gable roofs are more susceptible to wind uplift than low-pitch, hipped roofs.
- Fastening
Methods: The number, style, and frequency of fasteners (i.e., nails,
screws, or foam adhesives) can significantly shift the overall wind
resistance of the tile’s installation. -
Local Weather: High-Velocity Hurricane Zones, for example, experience a greater frequency of high winds.
- Incorrect
Installation: When installing concrete roof tile, it’s, of course,
important to follow the manufacturer’s published roof system
installation guidance for optimum wind protection performance, as well
as to ensure the warranty is valid. Incorrect installation, including
misaligned tiles, improper fastening devices, or poorly installed
flashing, can reduce the roof’s performance in high wind events.
Additional Industry Guidance
The
Tile Roofing Industry Alliance, which for 50 years has been the
industry’s voice for tile roofing code development, testing and
installation best practices, provides guidance and information for both
concrete and clay tile roofing options, as well as for wind resistance.
TRI Alliance’s information states:
“In regions prone to
tornadoes, hurricanes or extreme winds, roof tile provides one of the
best defenses against wind-related property damage.
- Concrete and clay tile roofing helps in resisting hurricane-force winds.
- Natural air ventilation under the tile created by its high porosity and installation techniques helps to relieve wind stress.
- Independent
testing sponsored by TRI Alliance shows that with proper attachment,
clay and concrete roof tiles can sustain winds in excess of 125 miles
per hour that would strip off most other roofing materials. -
Clay
and concrete tile roofing have been tested in accordance with Florida
Building Code – Residential, Sixth Edition, to meet SECTION R 4402
High-Velocity Hurricane Zones — Roof Assemblies and Rooftop Structures,
with wind speeds up to 150 miles per hour2.”
Wind Testing AND Building Codes
Though heavier in weight than many other roofing options, concrete roofing tile is highly durable and resilient in subtropical climates and high-wind regions. The tile is long-lasting and, with the benefits of its shape and construction, helps reduce wind uplift stresses.
Concrete
roof tiles are subjected to various wind testing measures in accordance
with performance standards to determine the resistance that a given
installation method meets for the design requirements in each region.
One of the world’s most stringent wind testing requirements is for the
High-Velocity Hurricane Zone of Southern Florida. Some of the wind
resistance tests for concrete roof tile include:
- ASTM C1568 –
08(2020) Standard Test Method for Wind Resistance of Concrete and Clay
Roof Tiles (Mechanical Uplift Resistance Method) - ASTM C1569 – 03(2016) Standard Test Method for Wind Resistance of Concrete and Clay Roof Tiles (Wind Tunnel Method)
- ASTM C1570 – 03(2016) Standard Test Method for Wind Resistance of Concrete and Clay Roof Tiles (Air Permeability Method)
- TAS 100, 101, 102, 102A, 108, 110 and 112 are all standards of procedures for testing the performance of tile roof systems.
Additionally,
the Southern Building Code Congress International (SBCCI) commissioned
Redland Technology to investigate wind loads on roofing tile systems
with the goal of developing a code methodology. Redland performed two
experiments to develop their design method3, and these were:
-
Wind
loads were estimated from wind tunnel tests where surface pressures on
medium and high-profile roofing tiles were measured as wind was blown
across a tile array - Wind uplift resistance was estimated
from constant displacement rate uplift tests that quantified the uplift
resistance of roofing tiles with various attachment methods.
The
resulting method was incorporated into the Standard Building Code
(SBC), and later the Florida Building Code (FBC) and International
Building Code.
Some concrete roof tile applications have been
tested to perform in sustained wind speeds up to 180 miles per hour when
installed according to industry and manufacturer guidelines.
Their
true advantage in wind resistance, however, is attributed to their
shape and construction, which allow wind to move freely through the
system, significantly reducing stress on the roof.
Today’s
concrete tile roofs provide exceptional curb appeal and, with an
extensive range of colors and profiles available, can meet almost any
desired architectural aesthetic. Though heavier in weight than many
other roofing options, concrete roofing tile is highly durable and
resilient in subtropical climates and high-wind regions. The tile is
long-lasting and, with the benefits of its shape and construction, helps
reduce wind uplift stresses.
While no roof will ever be 100%
windproof, concrete tile roofs are able to withstand both sustained
winds and more significant wind gusts, performing exceptionally well
against the wind when compared to many other roofing materials.
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https://www.roofingcontractor.com/articles/99108-an-examination-of-concrete-roofing-tiles-wind-resistance-capabilities
