LRWA VIEWPOINT
Working with liquids in winter:
what you need to know
Paul Franklin, technical secretary at the Liquid Roofing and Waterproofing Association (LRWA), dispels
misconceptions about using liquid waterproofing systems in winter and oers advice on safe and eective
application
As the fastest growing part of the
flat roofing sector, the liquid
waterproofing industry has
changed dramatically in recent
years. Now, an effective alternative to
other flat roofing systems, liquids are
being specified on a much wider scale
than ever before.
Yet despite this growth, there is still a
misconception among some contractors
that liquid systems are not appropriate
for winter use. However, as long as the
roof area is prepared appropriately, a
wide range of liquid products can be
applied in even the harshest weather
conditions.
Drying a roof
One of the biggest challenges in winter
is the potential for increased rainfall,
frost or snow, which can leave standing
rainwater on a substrate. This must be
thoroughly cleaned and dried before a
liquid waterproofing system is installed.
Although gas torches are still
commonly used for drying a roof, there
is a growing demand for solutions
which do not involve hot works, and
this has led to a variety of alternative
methods.
Removing standing water
If there is a lot of standing water, it is
possible for contractors to use a Bowdry
sponge roller to remove it. This tool
is used extensively for drying cricket
pitches, but works equally well on
roofs. The sponge collects the water off
the roof and deposits it into the water
collection receptacle.
This way of drying can work even
when the standing water is deep, and
any excess moisture can be removed
using a rag and mop, or allowing the
substrate to dry naturally.
The sponge roller also allows for
drying off quite rough substrates, such
as scarified and de-chipped surfaces,
however, operatives will need to responge
the roller more frequently on
rough surfaces.
Another option is to use a roof
pump. There are several different types
available ranging from electric to hand-
powered and even solar-powered. Roof
pumps are best used when placed in
the centre of a large ponded area, whilst
work continues on other areas of the
roof. They reduce the pond to around
2mm which can then easily be dried
using other methods.
New technology is also being
brought to market which can make the
drying process even quicker, easier and
safer. These include the E-torch, which
is an electrically-powered, computer-
controlled, high speed torch used to dry
roofs, thereby replacing the need for
conventional LPG gas torches.
Technology such as this is playing a
vital role in encouraging the industry to
implement a broader range of solutions
for drying roofs, which can be used all
year round.
Removing residual water
Once the standing water has been
removed, contractors can use
conventional leaf blowers to remove any
residual water. Alternatively, a Hot Air
‘Gun’ or ‘Blower’ could be used. As this
is electrical equipment, site electricity
supply and guidelines should be
considered to ensure compliance, which
may affect the choice of different hot air
equipment.
Furthermore, some of these machines
emit considerable amounts of heat and
extra care should be taken in certain
circumstances as they could also cause
deleterious materials to combust.
Additional attention to detail should
be expected on roof junctions, changes
in level and around plant and roof-
mounted equipment.
Daily planning
In winter conditions, pre-planning can
be extremely beneficial. Sheeting out a
roof area at the end of a day will enable
work to begin promptly at the start of
the next, preventing the need for further
drying or waiting for frost and ice to
melt before the liquid system is applied.
However, operatives must ensure
sheeting is weighted down to avoid
wind uplift and this should be avoided
altogether if there is a chance of
extremely windy conditions. The correct
material must also be used as polythene
sheeting, for example, can become very
slippery when exposed to wet or frosty
conditions.
Rapid curing options
In the past, one of the biggest concerns
about using liquids in winter was that
cold temperatures could slow cure
times. However, there are now various
quick curing options available. PMMA
systems for example, are proving
popular for winter use as most can dry
in 20–40 minutes even at temperatures
of around 0°C.
These systems tend to have a
minimum of two components. The coldapplied
liquid resin cures following an
extremely rapid in-situ polymerisation,
which is activated by the addition of a
peroxide catalyst.
Other options include polyurethane
liquid systems and flexible polyester,
which can both be applied with an
activator or accelerator to speed up cure
times in colder weather.
Hot melt systems are also suitable
for winter installation as can be applied
in low temperatures. These are applied
directly to a prepared structural deck to
create a completely seamless, monolithic
layer.
w www.lrwa.org.uk
The Alutrix
membrane
oers useful
temporary
waterproofing
during the snow
64 www.rcimag.co.uk November 2018
/www.lrwa.org.uk
/www.rcimag.co.uk
