22 | SEPTEMBER 2019
Installer Support
Installer Support is
sponsored by Kayflow
CLADDING REPAIR AND MAINTENANCE:
A TRADE-FOCUSSED GUIDE FROM SWISH
This month, Dave Osborne of PVC cladding specialists, Swish takes a look at external wall cladding
and offers some important dos and don’ts advice on cladding repair and maintenance.
As with other roofline
materials, most problems
with cladding start with rot.
We live in a damp climate
and timber cladding can suf-
fer badly and need replac-
ing if it doesn’t see regular
maintenance.
Here, we’re going to look
at cladding best practice.
Some do’s and don’ts that
will minimise the need for
future repair and mainte-
nance and ensure a good
standard of workmanship
for your customer.
First of all – choose the
right material for the job.
Softwood used to be the
favourite but cellular PVC
is now the best choice for
external cladding. It won’t
rot, it doesn’t need painting,
you don’t need special tools
to fit and it costs roughly
the same as timber. What’s
more, it will last the lifetime
of the building.
Swish cladding is a
foamed, cellular PVC mate-
rial with an integral smooth
and durable skin. It won’t
warp, flake or peel, nor
will it support bacterial or
fungal growth.
So, if you are faced with
cladding replacement be-
cause the old timber is past
its best, what’s the best way
to tackle the job.
1. Firstly, it’s best to re-
move all existing boarding
to get a good look at the
substrate behind. If the ex-
ternal cladding is in a poor
state of repair, the chances
are the battening behind
will be too.
2. Through ventilation
should be provided be-
hind the cladding, with an
unobstructed air path at the
top and bottom of the clad
area.
3. For white cladding, fix-
ing battens should be good
If you are faced with cladding
replacement because the old timber is
past its best, here’s the recommended
“Swish” way to tackle the job.
quality treated softwood
and a minimum 19x38mm,
although 25x38mm is better
as these create the recom-
mended 25mm ventilation
gap behind the cladding.
Batten fixing centres
should be set at 600mm for
buildings up to 2 storeys.
[400mm maximum for 2 to 5
storeys].
4. For foiled cladding,
battens should also be good
quality treated softwood and
a minimum of 50x38mm,
to create a minimum 50mm
airspace behind the clad-
ding. Fixing centre should
be 400mm maximum.
Continuity of the ventilation
path must be maintained by
omitting the starter batten
and by venting into the
eaves or by leaving a 10mm
air gap between the clad-
ding and the soffit. Angled
ventilators can be installed
at the base and top of the
cladding to prevent ingress
of insects.
5. Where additional
damp-proofing is required,
say for insulated timber
frame structures or in ex-
posed locations, it is advisa-
ble to use a breather mem-
brane behind the cladding.
White cladding and rainwater
systems in stunning combination
Stylish timber effect cladding from Swish
In timber frame construc-
tion a breather membrane is
essential. Where insulation
is installed, counter-bat-
tening will be necessary to
maintain a ventilated air
space. In case of doubt,
Swish technical staff will be
happy to advise.
6. Expansion gaps: As a
general rule, an expansion
gap of 4.0mm should be
allowed at each board end.
7. Fixings: For all cladding
profiles, 30mm, A4 stainless
steel fixing pins are recom-
mended.
8. Sealants: Where de-
tailing requires the use of
a weather seal to prevent
ingress of rain, snow, etc
for example at perimeter
junctions and openings,
Swish low modulus silicone
sealant is recommended.
9. Trims: A huge range
of cladding trims is avail-
able. These are designed
to ensure expansion gaps
are covered so that water
ingress is minimised and
a clean finish is achieved
around edges and openings.
Starter trims for the low-
er edge of the first plank
ensure a neat, professional
finish and universal chan-
nel can be used at all ends,
The perfect finishing touch.
abutments or around open-
ings. Two-part trims make
installation easier when
working with short-length
boards.
10. Finally: Make sure
all board-ends have the
correct expansion gap and
are properly fixed. Check
plumb and level every third
row as small deviation can
become visible over the clad
area. Also, do not butt ends
of cladding boards tight up
to each other and rely on
silicone as a suitable finish.
It will cause distortion, the
sealant will deteriorate and
it will soon look a mess!
Dave Osborne is Tech-
nical Manager for Cellular
PVC cladding specialists
Swish Building Products.
For more detailed guid-
ance, we also recommend
readers to refer to Swish
Design and Specification
Guide and to the Plastics
Industry Code of Practice,
available from The British
Plastics Federation.
www.bpf.co.uk
For more information:
Swish Building Products:
01827 317 200
www.swishbp.co.uk