Effective Fasteners for Metal Construction
With dozens of fasteners to choose from, which are the most
As the number of metal roofing
companies grow and as metal roof construction increases, the
selection of fastener screws available has also grown. Fasteners
are integral to the overall performance of metal roofs. Choosing
the most effective roofing fastener screw ensures energy efficiency
and quality workmanship, fulfills necessary uplift requirements and
minimum design loads, and promotes long roof life. Choose the wrong
fastener and your roof can fail.
Self-Tap to Self-Drill
Before the mid-1960s, if you were looking for the most effective
fastener screw for your metal roof, you probably found a
self-tapping fastener (A, AB, B). Today, there are still installers
trained on selftapping fasteners who consider them to be the most
effective way to attach panels.
Self-tapping fasteners usually have a 14-diameter hex- or
hex-washer head, and feature steel-backed, bonded rubber washers.
The washer assembly⎯not attached to the screw⎯moves to accommodate
any error in driving the screw. "If the fastener is driven a few
degrees off vertical (to the panel), the washer can move to provide
a seal," says David Webster, Leland Industries, Toronto. "Self-tapping
fasteners require drilling pilot holes in the panel and structural
material, a time-consuming step. The additional labor may negate
any savings when using self-tapping fasteners in preference to
self-drilling fasteners. Self-tapping fasteners are more likely to
be supplied with mechanical zinc plating, [which is] a thicker
plating. This is considered obsolescent by some, but is still
routinely applied to certain self-tapping fasteners."
Modern self-drilling fasteners come in a much greater variety
and many find them more effective for metal construction
applications and profiles. Webster says fastener diameters #8, #10,
#12 and #14 are the most commonly used and most effective with
lengths from 1/4-inch to 8 inches. There are at least eight
different head style types, the most common being some form of hex
washer head in 1/4-inch, 3/8-inch or 7/16-inch diameter.
Webster cites an advantage, often overlooked with self-drilling
fasteners, which is the hole size. "The size of the hole is the
shank diameter, an important advantage when sealing the hole made
by the drilling action," he says. "Choice of shank diameter and
head style allows for many fastening options. [There's] a choice of
head styles including low-profile heads for use with hidden
fastener panels. I believe the best all-around fastener for
attachment of metal sidewall or roofing panels will be a #12
diameter self-drilling screw with a point capable of drilling
through multiple laps of high-tensile sheet and the structural
member. The screw must penetrate the member to show a minimum three
laps of thread when seated. This will ensure that fully crested
threads are engaged to provide maximum holding power. The #12
fastener will feature a hex washer head with a washer face to bear
on the accessory sealing washer. The washer drives straight but
allows movement if the screw is driven off the vertical."
The type of metal panel being fastened largely determines the
most effective fastener. For instance, "Installing an R-Panel into
wood using a #10 Pole Barn Fastener with a Hi-Lo thread will
provide better pull-out values and if the fastener has a type-17
point then that allows for quicker/ easier drilling," says Ken
Fastener, Kansas City, Mo.
For metal-to-metal applications, choosing the most appropriate
fastener often starts with determining the total thickness of the
material being fastened. "Attaching roofing sheets to a purlin, the
#12 with a T-3 self-drilling point has a drilling capability from
0.036-inch to 0.210-inch total steel thickness," Webb says. "For
roof lap stitching, a 14-14 x 7/8 inch T-1 can be used. The T-1 has
a mini drill point that can attach total steel thickness of
0.024-inch to 0.095-inch. To attach roofing sheets to structural
steel, Dynamic Fastener offers a T-5 Fenderhead that can drill from
0.250-inch to 0.625-inch total steel thickness."
Keith Self, metal building product manager, Birmingham
Fastener, Birmingham, Ala., says other factors playing a role
in selecting the most effective fastener include where in the
project the connection is being made, the environment, and the
manufacturer and/or installer preferences. But he cites the most
common fastener for metal-to-metal applications is the integral
head, self-driller with an EPDM washer.
"Material thickness will determine the length and drill point,
but will typically be a 12-14 x 1-1/4 inch #2 point for
panel-to-purlin application, and a 1/4-14 x 7/8 for a
panel-to-panel [connection] commonly referred to as a 'stitch
screw' or 'lap screw,'" he adds. "On a metal-to-wood application,
the fastener of choice is a 10-12 x 1-1/2-inch type 17 sharp point.
These parts are typically a bonded washer variety and offered in
several different configurations. Twenty-five years ago, even the
self drillers were bonded washer parts, and even today, some
installers still prefer the older technology, because that is what
they are comfortable with and have used in the past. In roofing
applications a long-life head is preferred due to the fastener head
material, typically either zinc or 300 series stainless. They are
guaranteed not to rust."
Self-drilling fasteners come in many forms: zinc coated, zinc
aluminum cap or molded head fasteners, stainless capped screws, and
even bi-metal stainless screws with carbon-steel drill points.
Generally, the most effective fastener screws are those capped with
a non-corrosive metal or alloy to provide the longest life.
Stainless steel bi-metal screws need to be used when attaching two
dissimilar metals such as steel and aluminum.
"Fasteners that drill or pierce the metal panel from the topside
of the roof and attach to the deck structure must have sealing
washers made of EPDM to seal water from entering the building,"
says Joe Stager, vice president of Triangle
Fastener Corp., Cleveland. "Because the head of the screw is
exposed to weather, they should be plated or coated with a finish
that provides increased corrosion resistance than ordinary
zinc-plated fastener screws at a minimum."
When attaching hidden fastener panels for applications like
standing seam roofing, pancake head fasteners are often the most
effective. "These fasteners are designed to be protected from the
elements and are usually not coated with as thick a coating of
zinc," says Tim Martin, regional sales manager, Levi's Building Components, Leola, Pa.
"Stainless steel versions are also available. These fasteners are
covered by the next panel and are hidden from view. The heads on
these fasteners are very thin and should not telegraph through the
Alan Belcher, branch manager at Triangle Fastener's
Jacksonville, Fla., location, says #10 low-profile pancake head
fasteners are effective for clipless or nail-hem panels. Clipless
panels fasten directly to the roof deck. "The low-profile head is
less likely to dimple the panel covering the fastened side of
preceding panel when installed," he says. "A wafer head is even
better, but the tapered shoulder can impact the panel negatively as
Effective Selection Help
This is just a brief overview of some of the most effective
fasteners for metal construction. More detailed and thorough
information is available. Stager says associations like Metal
Construction Association publish documents on fastener selection.
Fastener suppliers are usually the first stop for help. Dynamic
Fastener has a 2017 Tool and Fastener Hand Guide to assist
customers. Belcher says Triangle has an app for smartphones on his
company's website for help.
"Most fastener suppliers have catalogs and websites that detail
the testing done on the fasteners, warranties and other technical
information about the screws available," says Martin. "Certainly,
fastener companies who offer a diverse array of
application-specific fasteners and back it up with a high level of
product and application knowledge, can be a great resource for
fastener purchasers," agrees Chris Ray, national sales manager for
Levi's Building Components.
Self stresses finding a knowledgeable company for advice; one
that can keep up with market changes. "Fasteners have changed over
the years, as have coatings, and even in some cases the materials
you will be attaching to, all this must be considered before
recommending a fastener for a particular application," he says.
"Just because a product worked yesterday, there are always advances
to the way we do things, better, faster and stronger the technology
of fasteners has improved. Fasteners typically are between 1 to 2
percent of project cost, it only makes sense to buy quality
products from a quality company that stands behind their products.
Finding a partner and building a mutually beneficial relationship
is key. In many cases it is not what you know, but who you
Leland advises attending trade shows and open houses
where exhibitors lay out large quantities of sales literature.
"Pick it up, take it home and read," he says. "Sales literature
contains much of what you need to know about the product. Talk with
a sales representative. Request a demonstration. Reputable
manufacturers can usually accommodate a job-site visit to show how
the product performs. New products are on display at trade shows,
and often the manufacturer is on hand with short seminars and
videos to show the product at work. Go online, it's amazing how
much information is available from the manufacturer."
Ray urges fastener customers to always consider the options and
review the advantages and disadvantages of each fastener, taking
into account factors such as quality and versatility as they relate
to the specific job. "Each application is unique," he adds. "Making
the right fastener selection at the outset will ensure end-user
satisfaction and product performance, and eliminate problems down