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5.1 visual
quality
It is recommended to use a
nail gun with a facility to adjust the pressure. The nail should
penetrate so that the head sits flush with the cladding surface (See
figure 11). Typically 2.1 or 2.5 is the recommended nail thickness
when using an airgun and improved nails. The use of improved nails
(annular ring shank nails) is recommended to improve nail holding strength
and to be able to use thinner nails to avoid splitting. For standard
nails, nail penetration into battens should be 2.5x the thickness of the
board being fixed. For improved nails (e.g. ring shank nails) nail
penetration into the batten should be 2x thickness of the board.
When nailing pay attention to the
following:
1. Using a hammer increases the risk of splitting
due to hammer contact with the wood.
2. Do not nail on knots.
3. If tongue and grooved boards are to be used, a
2mm clearance gap should be present between
the tongue and groove of the
joint. The gap is required to allow for settlement of the building
and
any potential movement due to
moisture uptake. A similar gap should be left between tapered
cladding boards.
4. If screws are to be used, pilot drilling is
always recommended.
5. Secret nailing with single nails should be
avoided for tongue and grooved ThermoWood® boards
because of the risk of the
tongue splitting although the risk of splitting can be reduced by drilling
pilot holes.
6. Nail fixing should be at least 25mm from the
ends and 30mm from the edges of the boards.
Always apply the edge and end
distance rules to avoid splitting. If forced to fix under the
recommended edge and end
distances always drill nail holes before fixing to prevent splitting of
the boards.
7. Nails should preferably be located as close as
possible to the quarter points in the board width
although the actual position of
the fixings may be determined by the board profile. It is important
that where boards are
overlapped or in a board-on-board pattern the nails fixing the outer
boards
do not penetrate the inner
boards. Overlap between outer end inner boards on board-on-board
cladding should be 20mm.
8. Cladding boards 120mm wide or above should be double
nailed. Boards under 120mm can be
fixed with one nail. The
nail should be placed on the lower part of the board.
9. In conditions where cladding boards are exposed
to heavy wind loading boards 100mm wide and
above should be double nailed.
10. Where boards are butt-jointed the junction should always occur
over battens. If 42mm wide
battens are used, it will be
necessary to double batten the position where cladding boards meet to
assure that nail fixing is at least
25mm from the end of the board (See figure 3).
nail types
Stainless steel nails should be used to
fix Finnforest ThermoWood®. Mild steel and even plated
nails can deteriorate when exposed to moisture and stain the area around
the nail head. A less visible lower gauge nail can be used but lower
pull through strength should be noted and additional fixings will be
required. 'Lost-head', 'small head' or 'siding nails' are suitable
for ThermoWood® but 'round-head' nails offer greater holding
power.
5.2 nailing positions
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