May 2019

Liquid Roofing & Waterproofing
THE REINFORCEMENT LAYER DEBATE
Sarah Spink, CEO of the Liquid Roofing and Waterproofing Association (LRWA), outlines the
advantages of choosing reinforced liquid waterproofing systems, as well as what contractors
should look out for...
There are so many liquid waterproofing
systems to choose from, it can often be
difficult to know which is the right solution
for your job. At the LRWA, we have seen firsthand
how projects have failed because the wrong
product was installed. In this article, we will look
at why reinforced liquid roofing systems are often
the better choice in certain environments.
Why use a reinforced system?
Over the years, the LRWA has seen some liquid
roofing manufacturers introduce systems without
a reinforcement layer – claiming to be more cost
effective and quicker to install. Reinforcement
layers are often made up typically of either a
polyester fleece material or a glass fibre mat.
Cold-applied liquids are predominately used in
refurbishment projects which are often installed
over the top of existing roofing systems. Because
of this, there is potential for more thermal
movement, putting the waterproofing system
under stress if reinforcement is not used.
Therefore, most liquid systems require full
reinforcement in refurbishment projects to offer
increased strength and durability.
Reinforcement also provides crack bridging
capabilities, particularly if a crack on the roof or
balcony substrate forms after the liquid
application. To bridge any cracks which may
develop, the overall strength of a full reinforced
system will be significantly higher than the
strength of the liquid resin alone. This means, if a
crack does form, a reinforced system will offer
more flexibility on either side of the crack, which
will lessen the stress on the roof as a whole.
However, if an unreinforced system is used, this
process would create more stress than
elongation, ultimately compromising the lifespan
of the system and potentially
causing it to fail. This can even
happen if a crack wasn’t present
at the time the system was
installed, as no resin coating alone
has infinite elongation capabilities.
Contractors should also be aware that some liquid
waterproofing systems sold without a reinforcement
layer often advise including reinforcing strips over
cracks, joints or points of stress to improve
performance in these critical areas, adding more
cost to a project without providing a full, seamless
reinforced system. It is therefore still advisable to
specify a fully reinforced system as the overall
performance of the solution is then consistent
throughout the entire project.
Reinforcement also ensures consistent thickness
of the waterproofing membrane. Having a liquidapplied
top coat with good adhesion to the base
layer and correct film thickness is really
important. In exposed applications, this layer
endures any potential foot traffic on the surface,
and has to withstand the weather conditions in
our varying UK climate.
There is an argument to suggest that in some
circumstances, reinforcement is not required.
Some non-reinforced liquid systems are often
used in new-build applications where structural
waterproofing is applied direct to concrete or for
coating metal profiled or asbestos cement sheets
The LRWA says there are many advantages to choosing
reinforced liquid waterproofing systems and contractors
need to be aware of these.
Contact the LRWA
0333 987 4581
www.lrwa.org.uk
@LRWAssociation
Left: Sarah Spink, CEO of the LRWA.
for example. In these cases, it is
always best to refer to a
manufacturer’s guidelines on what
substrate a partially or non-reinforced
system has been tested on.
Quality is key
Contractors should be aware of the quality of the
liquid product before they buy. Liquid
manufacturers should have a third-party
accredited quality management system such as
ISO 9001, which ensures the product is
manufactured to a consistent specification.
It is also essential for contractors to undergo
training of that particular liquid system, as every
product is different and may require alternative
installation techniques. Application guidelines
must be readily available from the manufacturer
as well as clear routes for system training for the
contractor. The LRWA also offers accredited
courses which are led by a specialist team.
Raising standards of liquids
The LRWA is committed to working with
merchants to help raise standards across the
industry, and we are currently working on a
project which could provide merchants and other
distributors with a tool enabling them to quickly
and easily assess the suitability of liquid
systems, including accreditations. New initiatives
like this, combined with more awareness and
training, will ensure that merchants, contractors
and manufacturers can provide and install liquid
waterproofing solutions which perform as expected.
40 TC MAY 2019