As Florida continues to tighten its code requirements for tile
roofs, the industry responds with new installation techniques
and training programs
by Charles
Wardell
After hurricanes Frances, Charley, and Ivan blew through Florida in
2004, the Federal Emergency Management Agency (FEMA) sent teams to
survey damaged homes and buildings. One of the most common problems
the teams found was failure of the roofing system. Although the
investigators saw failures with all roofing types, the tile
industry was the first to respond with new design criteria and
installation details. These details have since been added to the
Florida Building Code, and more code requirements are under
discussion.
Evolving Codes
This isn't Florida's first storm-driven code revision. The last one
was in 1997, five years after the devastation left by Hurricane
Andrew. Before then, most tiles installed on low-pitch roofs in
Florida had been set in a bed of mortar. Because so many of these
roofs failed in 1992, the tile industry developed alternative
installation techniques that could better resist high winds,
including methods for adhesive and mechanical attachment, which
where then included as options in the Florida code.
After Hurricane Andrew, Dow and Polyfoam both introduced a foam
adhesive that's much stronger than mortar and which is now used by
installers certified by each company. In addition, the Tile Roofing
Institute (TRI) developed guidelines for using smooth-shank nails,
ring-shank nails, and screws. According to TRI Technical Director
Rick Olson, the emphasis was as much on cost as it was on safety.
"Mortar was running $30 to $35 per square at the time, while our
options cost as little as $6 per square."
Installers quickly warmed to the new techniques. With few
exceptions, most post-1997 roof tiles were fastened in place using
one of these systems. The 2004 FEMA survey found that these roofs
had a much higher survival rate that those installed earlier.
In a tropical storm, hip and ridge cap tiles turn into deadly
projectiles. The solution is to attach hip and ridge tiles to a
ridge board, using screws through the tile that penetrate at least
1 inch into the board.
But some roofers continued to use mortar. Tim Reinhold with the
Tampa-based Institute for Business and Home Safety reports that his
organization had supported a code-mandated ban on mortar-set tiles
in high-wind areas, but he notes that opposition by roof installers
was too strong. As a compromise, the industry came out with a
code-approved prebagged mortar with just the right amount of sand
and cement.
The 2004 FEMA investigation underlined the weakness of mortar set.
Tom Smith of TLS Consulting in Rockton, Ill., who served on the
FEMA survey teams, says that the size of the blow-off area of
mortar-set systems typically was much greater than for tiles
attached with foam or mechanical fasteners. He advises against
mortar set, no matter what type of mix the roofer uses. FEMA's Home
Builder's Guide to Coastal Construction (http://www.fema.gov/rebuild/mat/mat_fema499.shtm),
published in June 2005, also recommends mechanical attachment
rather than mortar set in all high-wind areas.
Other industry groups agree. For instance, Reinhold says that
IBHS's Fortified … for Safer Living program, which certifies
homes as disaster resistant, has never approved a mortar-set roof.
"We've heard comments that tiles are so dense that it's hard to get
a good bond. We recommend against it."
Mortar-set roof tiles were easily stripped from an apartment
building in Punta Gorda by Hurricane Charley in 2004. To improve
attachment, both mechanical fasteners, such as screws or nose
clips, and adhesive foam are recommended for coastal
homes.
New Hip and Ridge Requirements
Mortar's weakness was further highlighted in 2004 by problems with
hip and ridge tiles. The 1997 code revisions had simply neglected
these. "Trim tiles had been treated as decorative accessories, so
they were not adequately addressed [by the code]," notes Olson. He
reports that many roofers were still setting hip and ridge tiles on
a bed of mortar, even where they had nailed or screwed the field
tiles. Over time, the mortar's grip on the hip and ridge tiles
weakened, leaving them without secure attachment. "They would blow
off and become airborne, bouncing across the roof plane, breaking
field tiles, and causing other structural damage." This happened
even on homes built to current code standards and even on homes far
enough from the beach to see considerably lower wind speeds. "We
realized that something had to be done," Olson notes.
Tiles properly secured with adhesive foam withstood the
onslaught of Hurricane Charley over Port Charlotte Harbor, Fla., in
August 2004. The only weak link was the rake detail. Best practice
calls for a rake board and battens, as detailed in the illustration
below.
Two-piece barrel profiles require a foam pad for the bottom
tile and a double pad for the overlapping tile, as shown. In wind
zones above 110 mph, exposures B and C, apply foam adhesive pad 1"W
x 1"H x 8"L per ASCE 7-98. The Tile Roofing Institute also
recommends ridge boards to secure ridge caps. Best practice calls
for nose clips to secure the eaves edge, which is most vulnerable
to wind uplift.
To solve the problem, TRI worked with the Florida Roofing, Sheet
Metal and Air Conditioning Contractors Association, Inc. (FRSA) to
develop new attachment guidelines for hip and ridge tiles. The new
guidelines were included in the latest edition of the TRI/FRSA
Concrete and Clay Roof Tile Installation Manual. The manual was
released in October of 2005, and adopted by the Florida Building
Code in November.
The new guidelines spell out how to properly install hip and ridge
tiles. On all tile roofs, the contractor now has to include wood or
metal nailers along hips and ridges, and the installer has to
securely fasten tiles to this board using screws, nails, or a foam
adhesive.
Nailers aren't a new idea, of course, but this is the first time
they have been required. "Most of the procedures we recommend are
not new; they have just now been put into a tremendously detailed
document," says FRSA Executive Director Steve Munnell. The new
manual's step-by-step instructions and diagrams for doing proper
hip and ridge tile installation were based, in part, on the fact
that roofs using these techniques fared much better during the
storms. "The folks in South Florida indicated that houses with
mechanically attached ridge and edge tiles did better," notes
Reinhold.
Updated Design Guidelines
TRI has addressed design as well as construction by beefing up its
Concrete and Clay Roof Tile design criteria. The old version,
published in 2002, had just one page dealing with high-wind
applications. The new version, released in July 2006, includes nine
pages of tables, formulas, and specs for areas subject to sustained
winds over 100 miles per hour. The tables let the designer
calculate uplift forces for various wind speeds on a given tile
based on roof type, height, and pitch, and then specify fastener
types for that uplift force for different tile profiles and
sheathing thicknesses. "We want to help designers select the right
options," says Olson. "For instance, one screw or nail per tile may
be adequate for areas subject to a certain wind speed, while the
tiles on a roof subjected to higher winds will need two nails. The
new criteria show them which they need when."
Going forward, TRI will also recommend further code requirements.
"Because of the complex architectural designs on many of today's
roofs, we're seeing an accelerated wind force against the front
edge of the roof," explains Olson. "Because of this, the first
course down to the eaves has a lot more potential to pop off [than
the courses above it]. By the end of the year, we hope to analyze
and find a better way to attach those tiles."
To keep rake tiles from becoming windborne debris, secure edge
tiles along the rake to battens, as shown.
Installer Training
Ever-stricter codes bring the challenge of training installers to
follow them, however. Although the TRI/FRSA guidelines have been in
place for a year, for instance, Olson says that many roofers and
contractors still don't understand them.
In fact, some installers aren't even following the 1997 guidelines.
The FEMA teams found some roofs with mechanically attached and
foam-adhered tiles that didn't perform as predicted. Olson, who
also studied failed roofs after the storms, says that the culprits
involved installation problems on both foam and mechanically
fastened roofs. On the foam installations that fared poorly, Olson
discovered that installers hadn't followed the foam manufacturer's
instructions. They used too little foam or didn't put the foam at
the right locations on the tile, or both. With the failed
mechanically attached roofs, the problem was not enough fasteners,
or fasteners of the wrong type.
Foam manufacturers have responded by meeting with the installers of
problem roofs. In some cases, they have made those installers get
recertified to use the system. TRI has also launched a nationwide
training initiative to help remedy the problems. According to
Olson, the institute plans to have completed four trainings by the
end of this year, and it will add programs wherever 50 or more
attendees sign up. (Cost is $195 for TRI members and $295 for
nonmembers.) The two-day program covers installation practices for
the entire country but also includes a section on high wind. TRI
will also offer a special high-wind training program to Florida
contractors in January and February 2007.
Both training programs go beyond fastening. Issues covered
include:
- How to properly lay out a complex roof so that the courses are
straight and meet in the right places. "A lot of installers are
used to straight gables, but today's roofs are architectural focal
points with features like dormers and different levels," Olson
explains.
- How to properly flash tile. Because of their profiles, tiles
often don't sit flat against the roof, and many are installed on
battens. Olson has seen tile installations by people not familiar
with these conditions in which the flashing actually directs water
under them. "Ninety percent of the callbacks we see are flashing
related," he notes.
- How to properly fasten tile. Often the fastening tables say to
use two screws, but the installer uses only one. Or the installer
fastens the tiles with the same 8-penny nails used for the battens,
when they're supposed to use 10-penny nails. "It's all because
people are in a hurry and they don't think anyone will notice. We
want to teach them the importance of following the
guidelines."
"There really isn't a training school for these guys," says Olson.
"This country isn't like Europe, where there's a long tradition of
craftsmanship. And after storms, we see a lot of transplanted
roofers from other parts of the country who might not be familiar
with how to install tile in Florida. We find that a lot of bad
habits get passed down." ~
Charles Wardell writes on construction topics
from Vineyard Haven, Mass.
For More Information
The Fourth Edition of the FRSA/TRI Concrete and Clay Roof Tile
Installation Manual can be ordered from the Florida Roofing, Sheet
Metal and Air Conditioning Contractors Association, Inc., http://www.floridaroof.com ; 407-671-3772. This manual
covers the proper attachment methods for concrete and clay tiles in
high-wind zones, using Florida construction standards. An online
copy is available free from the Tile Roofing Institute (http://www.tileroofing.org/uploadedFiles/TRI_SITE/Become_a_Member/Florida%20Manual.pdf).
The Concrete and Clay Roof Tile Installation Manual for Moderate
Climate Regions, which covers best-practice installation methods,
industry standards, and code requirements, can be ordered from the
Tile Roofing Institute, http://www.tileroofing.org ; 312-670-4177. Cost
is $10.
Foam adhesives come with specific recommendations for installing
tiles with their products. For more information, go directly to the
manufacturer: Dow Chemical's Tile Bond: http://www.dow.com/buildingproducts/tilebond Polyfoam
Products' Polyset One: http://www.polyfoam.cc/products/roof/polyset1.html