January 2020

An Inspector Calls
DON’T LET YOUR ROOFING
PROJECT END UP IN THE GUTTER...
In our regular monthly column – ‘An Inspector calls’ – Total Contractor has teamed up
with the pitched and flat roofing experts at BMI UK & Ireland to help you avoid the
common pitfalls that can often cost you both time and money, and ultimately help
you achieve roofing success.
This month the Inspector looks at the
consequences of allowing underlay to
drape into gutters.
There was a time when this particular error was
seen everywhere on the eaves of pitched roofs. To
ensure the flow of rainwater from the underlay to
the gutter, it would be left to overhang the roof
and draped into the gutter itself.
It seemed like a good idea at the time, yet it was
a costly mistake. Most will now know that draping
underlay into a gutter allows liquid to be drawn
back into the roof. It will degrade the bottom
edges of the membrane itself, eventually start to
rot the fascia boards and ultimately will create an
area of negative fall and ponding beneath the first
few courses of tiles.
Hard work from a simple oversight
Contractors have spent years repairing and
replacing underlay, facias and even supporting
timbers thanks to the
damage caused by this
simple oversight. It’s
taken some time, yet
on the whole the
sector has come to
learn this lesson and
underlay support trays
are now commonplace in
the market. A simple, lowcost
solution to this problem, the
tray creates a solid base for the bottom edge of
the underlay to sit upon and replaces the old
underlay drape as a method of allowing rainwater
“Most will now know
that draping underlay
into a gutter allows
liquid to be drawn back
into the roof”
Left: In the gutter – underlay will
perform badly in the long run.
to drain off from the
roof into the gutter.
Because it does
involve some extra
work and some
(marginal) extra cost,
there will still be a few
installers who choose to work in
the old-fashioned way and one still has to
inspect roofs where the drape is in place.
So, it’s advisable not to take this shortcut. It is
not only very damaging to the long-term
performance of the roof, it is also highly
noticeable and is almost certain to be picked up
during any kind of sign off or inspection, not to
mention spoiling the overall look of the job.
Avoid unnecessary headaches
In this day and age, where all roofs are fully fixed
and all perimeters such as the eaves are twice
fixed, this is no longer a simple solution to
rectifying this problem. Having to disturb an
entire double fixed row of tiles could result in
having to not only supply new trays and tiles, but
also facias as a result of damage caused by
existing penetrations. Our advice would be to use
underlay support trays to avoid this unnecessary
headache.
Above: Don't be a drip – underlay installed incorrectly.
Contact BMI National Training Centre
01285 863545
www.bmigroup.com/uk
@_Redland / @Icopal_UK
16 TC JANUARY 2020