All cutting
should be carried out at ground level, not on the roof or over other
materials which are to be used in construction. This will help
fulfil Health and Safety guidelines and ensure swarf and debris are
not deposited on the panels, where it can cause discolouration and,
potentially, corrosion. If it is not possible to cut at ground
level, a scrap panel should be used to protect the roof cladding.
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Cutting
composite panels with an appropriate saw. |
In the case of composite panels,
the use of a jig or circular saw for cutting is necessary and must
therefore be carried out with utmost care. It is essential to use a
cutting speed which will reduce the effects of frictional heating on
the coating, and care should be taken to produce the best standard
of cut possible. A number of saws and blades are now available
specifically for the cutting of composite panels. However caution
should be taken when using these tools to provide an even. high
quality finish.
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| Damage to
pre-finished steel sheet caused by oxyacetylene torch |
The use of an oxyacetylene torch to
burn through the sheet is also an unacceptable method. This is
because not only does it produce a poorly finished an uneven cut,
bit also high temperatures cause severe damage to the coating.
All swarf and other debris must be
removed immediately from the coating surface since they can cause
abrasive damage, discolouration and potential corrosion.
Site sawn edges produced to
less-than-optimum standard may cause or accelerate cut edge
corrosion or peel back of the coating, and will be excluded from
warranty. All site sawn cut edges should be protected from
weathering with a suitable lacquer.
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A clean cut
sheet edge and neat sheet lap |
Protecting site-cut edges
A cut edge is an area of exposed
substrate where a pre-finished steel cladding panel has been cut. To
prevent problems with cut-edges, all exposed site-cut edges must be
produced to an optimum standard. Where it is not possible to protect
the cut edge from weathering by means of a cover flashing, the site
cut-edge should be treated with a suitable edge protection paint or
lacquer. Cut Edge Protection Lacquer Is
available from SLE Cladding Ltd.
Burrs at cut edges should be
minimised by effective shearing practice. Where possible the down
burr edge should be on the down slope of the roof pitch. In the case
of any cut-edges, the requirement for this sort of protection is
particularly important in highly aggressive environments such as
marine and industrial. It is also particularly important in the case
of low and very low pitched roofs, where the time of wetness is
increased.
NOTE. When
cutting sheets to customers required lengths, SLE Cladding
Ltd use the same cutting method (Guillotine) as do the sheet
manufacturers, so that under normal circumstances sheet edge
protection is not required.
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For more
information on Cut Edge Protection & Lacquer |
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Protecting Penetrations in a Sheet.
Penetrations consist of any breach in
the cladding, usually holes drilled or cut for pipework or other
accessories. A penetration made in a cladding panel effectively
leaves a site cut-cut edge and an area where water may ingress into
the cavity of the building. To ensure that the penetration does not
compromise performance, in the first instance the cut edge should be
protected as described earlier. The area around the penetration must
also be protected further by sealing using a suitable component to
prevent ingress of water into the cavity of the wall or the
building. In the roof cladding applications, suitable sealing
components should allow water to be channelled around any
penetration to prevent ponding.
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| A typical roof
penetration to insert a roof light |
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