| Our
polycarbonate sheeting can be fitted vertically,
for the sides of a greenhouse or porch, or even
a partially enclosed carport. More often however,
it is used on a roof with a gentle slope to permit
the easy run-off of rainwater into guttering.
The minimum slope should be about 10 degrees.
The
sheets have a natural tendancy to expand and
contract as temperature changes take place and
for this reason they are fitted into special
glazing bars down the long edges that are specially
designed for this movement. The aluminium glazing
bars are screwed to timber supports(joists)
at a maximum of 1050mm centres for 16mm sheet
thickness and a maximum of 700mm centres for
10mm sheet thickness.
The
deduction of 20mm for the centres dimension
allows for fitting into the glazing bars and
sideways expansion. Once laid in the glazing
bars the sheets are held in place with a snap
down pvc top capping cover strip - diagram A.
More
often than not, sheets will be cut to width
as described later but the 20mm reduction in
width between the glazing bar centres must always
be taken into account - Diagram B.
Diagram
B
Effective
supports-(purlins)-across the sheet width should
be at maximum 1500mm centres so roofs constructed
with 3m long sheets would only require one purlin
with 4m sheets requiring two. In
general it can be said that mechanical fixings
are not required for fixing roofing sheets when
glazing bars are used. However, in view of extreme
weather conditions which have prevailed in recent
years, you may need to consider that some mechanical
fixings are used for extra security. These are
limited to one button fixing at the bottom of
each sheet in the centre and fixed to the front
fascia, and one to each purlin, again in the
sheet centre.
The
starter hole for button fixings should be made
in the centre of the sheet cavity rather than
through a wall(if possible) and it will need
a 16mm diameter hole.(Hole saws available) This
is larger than the actual button size but allows
for expansion. When making the fixing ensure
that the foam washer is in place under the button.
Drive in the screw and fit the cover firmly
without over tightening as this could lead to
sheet distortion. Diagram C.
Diagram
C.
Cutting
& Preparing Polycarbonate Sheeting
Polycarbonate, despite its strength can be cut
using a fine tooth panel saw. When cutting to
width, you should endeavour to cut just to the
outside of one of the walls as in diagram D.
Diagram
D.
When
supplied, the sheets have protective polythene
film coverings on each side. Do not remove the
polythene films until the sheets are cut and
ready to fit. The side of the sheet with the
printed polythene MUST be fitted to face upwards.
If the polythene is mistakenly removed too early
and you do not know which should be the top,
look carefully at the end of the sheet. The
cavities are very slightly shaped as in diagram
E and the shaped skin is the one with the special
built-on long life protective layer which must
be uppermost. Both ends of the sheet should
be supplied sealed to prevent the entry of dust
and dirt during transit.
Diagram
E
When
cutting to length the 'top' end should be taped
with aluminium foil or breather tape so that sheet
has a permanently sealed top end. The bottom cut
end of the sheet should be fitted with our anti-dust
breather tape - available in 33m rolls-and then
a pvc end closure- diagram F.
Diagram
F
Cutting
will inevitably create swarf in the cavities and
this must be removed. This is best done with a
suction type vacuum cleaner, but if this proves
ineffective, remove the top sealing tape and blow
through the flutes with a pressure air line. Reseal
the top and bottom end. Every care should be taken
to avoid getting moisture in the flutes. Do not,
for example, leave sheets with open edges lying
on damp grass. Store them in a dry place. Under
no circumstances try to remove dust or swarf with
water. After fitting the sheets the end closure
is fitted between the glazing bars. This is done
as in diagram F with a fine line of silicone used
to secure the end closure to the sheet. Small
holes should be drilled in the bottom of the beads
at 500mm centres to allow any trapped moisture
to escape. Screw fix the end caps supplied with
the glazing bar to conceal the ends of the aluminium
glazing bars between the bottom cover strips for
a neat finish-diagram G.
Diagram
G.
Wall
End Fixings
On a sloping roof butting up to a house wall the
joint between the wall and the polycarbonate is
sealed using flashing which runs along the house
wall where it is cut into a mortar joint normally,
and at the bottom end, overlaps the polycarbonate.
At the end of a lean-to conservatory, the outside
edge of the glazing is covered by a special 'F'
profile which also protects the top of the gable
end cladding. The 'F' section is fitted on the
edge of the sheet - Diagram H.
Diagram
H.
If
an 'F' profile is fitted to a wallplate running
down the house wall the same special 'F' profile
is used to cover the joint adjacent to the wall.
Once the 'F' profile is fitted, flashing is run
down the wall and overlaps the 'F' profile.
Sealants
& Flashing.
Although our polycarbonate sheet is extremely
tough and herd wearing, as with other thermoplastic
materials, it can be adversly affected by chemical
agents. Care must therefore be taken when choosing
items such as sealants and flashing that will
come into contact with the sheet. |
