Generally the most common cladding style due
to the wide range of choice in terms of suitable
board profiles (all available profiles can be used
given the right design), the option of open or
tight (flush) joint types and the ability to cover
large areas either by staggering end joints to
create a ‘brickwork’ type effect or aligning them
to give a more ‘panellised’ effect.
Fixing battens only need placing vertically.
Boards should be no more than 150mm wide,
allowing a vertical overlap of at least 25mm for
square or feather edged boards and 15mm for
rebated or shiplap boards (used where a flush
surface is required).
Tongue and groove boards should have a
reduced coverage than overlap or rebated
boards. The tongue should face upwards with
the shoulder of this edge chamfered whilst the
trailing edge with the groove should be left
square and not vertically jointed.
Horizontal boards can be used open jointed as a
rainscreen with the top and bottom edges
chamfered at different ends, thus reducing air
pressure and wind driven rain. If the edges are
overlapped this will also reduce any possible UV
effects on the membrane. This design gives a
strong shadow line that will tend to hide the
effect of shrinkage if the boards are used green.
The attractive chevron designs that can be
produced with diagonal cladding make this
style a popular choice although it does carry
several design limitations. Longer spans of
board are required for the main diagonal axes
and this may necessitate either use of a thicker
board or close batten centres (no more than
400mm) to compensate. Butt jointing of shorter
boards should be avoided as these are liable to
leakage, as should arranging the boards in a ‘V’
profile as this can give drainage problems due
to collection of water runoff at the bottom.
If a chevron effect is required the boards should
be arranged as an inverted ‘V’, allowing the
water to drain away from the centre.
As a diagonal design is more vulnerable to
water penetration a flush fit is required.
Therefore open joints should be avoided and a
shiplap board profile is preferred.
This style is ideal for curved surfaces, using
narrower boards the sharper the curve, and is
also very tolerant of variations in dimensions.
In addition a variety of surface modelling can be
achieved by using the ‘board on board’
construction method - where a layer of inner
boards are spaced apart over the battens and
an outer layer of boards are fixed over these to
cover the gaps - by varying the widths of the
inner and outer boards.
The ‘board on board’ construction method also
allows for good ventilation and an open jointed
design can be used here, although this will
allow more rainwater penetration than with a
horizontal arrangement. Rebated or tongue and
groove boards will give a flush vertical joint
ensuring that there is enough overlap to allow
for shrinkage. Square cut timber can be used
but requires a minimum 25mm overlap.
Vertical butt joints should be avoided due to the
risk of swelling in the end grain of the lower
boards where joints are not completely flush,
therefore the available lengths of different
timber species need to be considered.
If boards are tight jointed then horizontal
bearers and vertical counter battens are
required. Batten centres should be no more