In the drink!
Designing in fl ood-resistance
In a newbuild situation, the best way to stop
water penetrating is to ensure that all concrete
used is waterproof, and to seal all construction
joints with specifi cally designed proprietary
tapes. Services coming in through walls and
fl oors should be designed to be watertight.
As a second line of defence, and if budget
and circumstances allow, a cavity drainage
membrane can help with the management of
fl ood water. A cavity drainage membrane, such
as Oldroyd, directs the water down the walls
into a perimeter drain with the water running
to a sump, where it can be evacuated using a
pump. This type of approach is also popular
as a retrofi t measure to
Phase 1 Footings & Foundations
Phase 1 Phase 2
It could be thought that, fl ood-wise,
the winter of 2016 was something of a
let off, being relatively warm and dry,
given the events of 2015 and 2014. As
was 2017, although there is still time
for 2018 to become wet – with summer
fl ooding now not unheard of. The year 2014
saw Somerset and the Surrey and Thames
river valleys under water; while the following
year it was Cumbria, north Lancashire and
Northumbria that got hit worst.
Despite these winters’ reprieves, the reality
is that extreme weather events are increasing
– look at the Caribbean and southern United
States recently – and, according to the
Environment Agency, there are over fi ve million
homes in England and Wales that are at risk of
It has been the case that design solutions
for fl ooding were described as either ‘fl oodresistant’
or ‘fl ood resilience’.
However, use of these terms had
become muddled and occasionally used
interchangeably. Consequently, less
mistakeable terms are now being employed,
namely: ‘water-exclusion strategy’ (i.e.
resistance), and ‘water-entry strategy’ (i.e.
A ‘water-exclusion strategy’ house is built
so that water cannot get into the building and
cause damage. A ‘water-entry strategy’’ means
constructing the house so that although water
may enter, the impact is lessened, structural
integrity is maintained and drying and cleaning
is made easier.
The likely depth of fl ooding will impact
on the choice design. For low water depths,
a ‘water exclusion strategy’ typically is
recommended. A ‘water entry strategy’ is
needed for higher water levels – a difference
in water level of over 0.6m between inside and
outside can cause signifi cant structural damage
to standard masonry buildings.
In practice, a pragmatic combination of both
is taken because it is often either prohibitively
expensive or impractical to provide a
completely fl ood-resistant building – especially
in cases where fl ood protection is being
retrofi tted to existing buildings.
While recent winters have been relatively dry, that’s no reason to become
complacent about fl ooding – especially in prone areas. So, when new homes
are being built in areas at risk, building in line with ‘water entry’ or ‘water
exclusion’ strategies must be taken into consideration. Hudson Lambert,
director at Safeguard Europe, reports
42 Summer 2018