Multiwall polycarbonate sheets are classed as self-extinguishing.
TWINWALL sheets have an exceptional fire performance and importantly
do not give off toxic gases. Twinwall has been tested in many
countries. In the UK it obtained the requirements of BS476 Part
7 and Part 6, Class 1 surface spread of flame.
Although light in weight, TWINWALL is approximately 200 times
stronger than glass and virtually shatterproof. This ensures that
it has the highest impact resistance of all the thermoplastic
A TWINWALL sheet will retain 80% of its impact resistance after
a period of 10 years. This excellent resistance to impact damage
exists over a wide temperature range and minimises any damage
that may occur in handling, transport and installation.
TWINWALL sheets can be cold bent and used in many curved applications
e.g. arched walkways. TWINWALL must always be bent longitudinally,
never across the width of the sheet.In applications of this nature
it is important not to place excessive tension on the sheet. Therefore
when TWINWALL is cold curved the minimum radius should not be
less than 150 times the thickness of the sheet i.e. 9OOmm.
TWINWALL is supplied with a protective film on both sides of the
sheet. The film carries labels that indicate which side of the
sheet is co-extruded with UV protective film. This surface should
face the sun when installed. The protective films must be kept
on whilst installing and working with the sheets. They can be
removed when the work is complete. This will help avoid any damage
We recommend that sheets are stored in areas not exposed to the
sun's rays. This can cause high temperatures to develop inside
the sheet and make the protective film difficult to remove. Extreme
heat could also cause distortion in the panels.
Sheets can be cut with a stanley knife, a fine tooth saw or a
circular saw. Alternatively, a hand saw held at a shallow angle
may be used. When cutting polycarbonate sheet it is important
to hold the
sheet firmly to prevent stress and vibration.
Drilling and fixing
Sheets can be drilled using normal drills bits, however the sheet
must be supported firmly underneath. It is important to allow
for thermal expansion, so holes for fixing should be drilled 2mm
larger than the screw shaft. Any dust or chippings must be removed
from the inside of the sheet using compressed air. PSP TWINWALL
fixings should be used to secure the sheets.
Taping and capping ends
The top and bottom ends of the sheet must always be sealed with
a breathable aluminium adhesive tape. This tape is available from
PSP Limited. The tape should then be protected using PSP's polycarbonate
end cap. This procedure will prevent any insects, dust or dirt
penetrating the inside of the flutes and will help reduce condensation.
The Snap Lock system employs a two-section polycarbonate joining
mechanism to greatly simplify the attachment of TWINWALL sheets.
Under this system the bottom half of the two-piece joint is bolted
down to a purlin. Twinwall sheets are placed on either side of
the joining mechanism and the top half is clipped in place to
secure the sheets firmly together. Leave a gap of 3mm between
the edges of
the sheet and the glazing bar to allow for thermal expansion.
TWINWALL sheets there are a number of things to consider:
* All sheets must be installed with the flutes running vertically
* Roofs should always have a minimum slope of 100 to allow water
to run off
* All glazing systems, sealants, gaskets and other materials must
be fully compatible with polycarbonate
* It is imperative that at least one rib of the sheet is engaged
and clamped in the glazing system
* A frame of approximately 15mm is normally required when glazing.
It is also important to add extra space for thermal expansion
* When drilling holes, thermal expansion must be taken into account
(ensure holes are 2mm larger than shaft of screws)
* Sheets must not be fixed or clamped too tightly as this will
prevent thermal expansion and contraction and will adversely affect
* Twinwall sheets should normally be fixed to purlins or studs
erected at a maximum of 600mm centres. In areas exposed to high
wind, spacings should be reduced to 400mm centres.
Do not walk
on TWINWALL sheets at any time. Always use a crawling board placed
across several supports.
We recommend that TWINWALL polycarbonate sheets are cleaned twice
a year. To clean the sheets we recommend using a solution of lukewarm
water and an ordinary household detergent or mile soap. A soft
Sponge or cloth should be used to remove any dirt and grime from
the sheet. Do not scrub the sheet with brushes or sharp instruments
and avoid any abrasives or cleaners of a highly alkaline composition.
PSP's TWINWALL sheets carry a ten year limited guarantee (see
your glass or builders merchant for details).