January 2020

Fixings & Fasteners
RIGHT FIRST TIME: A GUIDE TO
FASTENERS AND FIXINGS
Fasteners and fixings are very often forgotten about in the build chain and are either a lastminute
consideration or left to the contractor’s discretion. However, when fasteners are
correctly specified from the outset, there are huge benefits down the line. Neil Kirwan,
Specification Manager at SFS, explains how to treat specification of these products.
Specifying fasteners and fixings correctly
the first-time round is critical to ensuring
the fastening system remains robust
throughout the lifetime of the roofing system or
building envelope. However, fasteners are often
not specified until Stage 4 in the RIBA plan of
work, when the fastening system has already
been determined. It’s often up to contractors to
price the work, and they can end up cutting
corners with the fasteners and fixings.
By engaging higher up in the build process chain,
the correct fasteners are matched to perform with
the fastening system and the material it is
securing as well as the substrate that the
fastener is securing down to, improving total cost
of ownership and efficiency of the system.
How to specify a fastener or fixing
The specification of the fastener, despite being
such a small component, is critical if the roofing
and cladding system is to perform its required
function throughout the full term of the system’s
service and design life.
There are five principles of fasteners: durability,
weathertightness, airtightness, aesthetics and
structural performance. Each particular
application will need the fastener to comply with
at least two or three of these functions and often
will need all five. Failure of the fastener to satisfy
these functions may lead to the inevitable, and
sometimes catastrophic, failure of the system or
very costly remedial works. The key is to specify
on an individual basis, selecting the appropriate
fastener for the specific use.
“By engaging higher up in the build process
chain, the correct fasteners are matched to
perform with the fastening system and the
material it is securing as well as the substrate
that the fastener is securing down to”
The different types and classes of
fasteners
There are a multitude of fasteners available on
the market, each one designed for a particular
use. These include self-drilling fasteners, selfcoring
fasteners, self-threading fasteners and
clamping fasteners.
To avoid failure of the roof system, both the type
of fastener and its material must be considered
early on in the design phase. Coated carbon or
austenitic stainless-steel are the two main
materials used in manufacturing fasteners and
fixings. Coated carbon steel rapidly corrodes upon
exposure to humidity and polluted environments
and whilst surface coatings with excellent
corrosion resistance can be applied to prolong a
fastener’s life, this will only slow down the
corrosion process. Good industry practice is to
use austenitic stainless-steel fasteners in
combination with galvanised steel purlins to
avoid bi-metallic reactions.
What should be considered during the
specification stage?
In order to ensure the fastener and fastening
42 TC JANUARY 2020