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1.1
calculate the number of sheets required
The sheets are laid side
by side and overlap each other
The width of the sheet is now 0.686mm wide
Take 5.00m / 0.686 = 7.28 sheets are needed to cover ONE elevation
Since one cannot order 0.28 the number is always rounded up.
Thus 7.28 sheets becomes 8 sheets
Now we know that to cover one elevation of the above roof we will
need 8 sheets.
To cover both elevations will require 16 sheets.
1.2
Calculate the length of the each sheet
We know that we need
16 sheets but we need to tell the supplier how long each sheet will
be for the roofing replacement.
From the drawing we can see that the length of the sheets should
be 2.5m long each.
Tip:
- Always
insist on full length sheets. In other words sheets that span
from the top of the roof down to the gutter.
- Sheets
that are joined head-to-tail will reduce the life span of the
sheet
- Sheets
can be delivered up 21m in length
- For
lengths longer than this, a mobile steel mill is moved onto site
and the sheets are rolled onsite.
1.3
Determine number of linear meters
From our above example
we know that we need to order 16 sheets, each 2.5m long.
If we multiply 16sheets by 2.5m we get 40 linear meters.
In other words we get 40 running meters.
1.4
Calling for pricing
- When calling for costs,
the supplier will ask how many linear meters of Zinc alume roof
sheets you are looking for.
- They will supply an
Ex Vat price per linear meter.
Lets say you are offered a price per l/m of R50-00
Then we know that R50-00 x 40 l/m = R 2,000-00
So our 16 zinc alume roof sheets will cost R 2,000-00 Ex Vat
1.5
What other information will the supplier request?
Before
supplying a price the supplier will need to know some extra information:
- Thickness of the sheet
Zinc Alume Steel is supplied is thicknesses of 0,47mm and 0,53mm
We recommend using 0,53mm
- They will also want
to know if you would like colour on the sheet
Colour on the sheet is added at the factory and increases the
per l/m price of the sheeting
The paint layer is purely for show only and adds little to no
protection to the sheeting
- They will request
the profile of the sheets (In our case IBR)
- They will request
a delivery address
- Delivery is usually
free
Tip:
- When
ordering the sheeting find out about the warranty. Zinc Alume
sheeting is warrantied by Blue Scope Steel in Australia.
- They
will supply warranties between 5 and 15 years depending on the
site location.
- Factors
such as how close to salt air or heavy industry come into play
when they determine the warranty length.
Step
two - Material ordering
While
the sheets are being ordered some other items will also be required
2.1
Roof fixtures
- We recommend using
self drilling screws as opposed to nail in fixtures.
Self drillers can easily be removed when doing a roof replacement.
- Nail in fixtures can
be removed but this needs to be done with a crow bar / hammer
- Self drillers come
with a separate self sealing washer
- Nail in anchors also
come with washers but these can be easily damaged with the hammer.
One missed hammer blow will damage the sheet.
This problem does not occur with self drillers
You
will need to get a hex head fixture for a drilling machine.
Self drilling roofing
fixtures go into either wood or steel but not both. You need to
specify what material you will be going into.
Class one, two, three,
four are ISO ratings for self drilling screws.
If you would like to
purchase Class 1,2,3 and 4 self drilling screws you can speak to
one of our consultants by clicking
here
Zinc
Alume sheets must be fixed with class 3 or 4 fixtures
in order for the warranty on the sheets to be valid.
Class four fixtures are
used in heavy industry / salt spray environments.
2.1.1
Determine the number of screws per l/m
A general rule of thumb
is 4 fixtures per l/m of Zinc Alume for roof replacements.
In our example we have 40 l/m and would thus order 160 fixtures
2.2 Insulation
In summer steel roofs
can become very hot. Heat is transferred into the roof space and
then into the house. In winter the reverse is true.
Isotherm (link) is a
loose laid insulation blanket that is an effective insulator
Various brands of metal
foils are available
This is thin foil sheeting that is first laid down on straining
wire
The sheets are laid ontop of the foil and heat energy transfer is
lowered
White
roof sheets
White roof sheets reduce
heat energy by 30%. The reverse does not apply to winter.
2.3
Steel and rubber closures
Order one of each closure
for each sheet
Closures help for keeping
wind driven rain from entering the ridge. They are effective but
not waterproof. They also help keeps birds and dust out
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