Expansion

Q. Nailed batten fixings are working loose for our 12m long curved sheet metal roof. How much will corrugated sheet metal roofing expand?

A. Metal expands at a rate related to the change in temperature. This change in tempertaure will be afftected by the colour of the roofing. ON a hot summers day without breeze metal roofing may reach 50 Deg.C in off-white, 60 Deg.C in zincalume and 80 Deg.C in Ebony.

Expansion will occur from the centre and for each fastener it will occur towards the end of the sheet. Expasion is linear. Lysaght advises in their Roofing and walling maunal the following

5m 0.6mm @ 10Deg.C change, 3mm @ 50Deg.C change, 4.5mm @ 75Deg.C change
10m 1.2mm @ 10Deg.C change, 6mm @ 50Deg.C change, 9mm @ 75Deg.C change
15m 1.8mm @ 10Deg.C change, 9mm @ 50Deg.C change, 13.5mm@ 75Deg.C change
30m 3.6mm @ 10Deg.C change, 18mm@ 50Deg.C change, 27mm @ 75Deg.C change

Some examples:
The deep pan concealed fixed Stratco Topdek 700â„¢ and Fielders KingKlip in their material specifications, both say for 0.42(33.32kg/lin m) and 0.48(3.76kg/lin m) BMT there is 2.9mm average per 5 metre at 50 degrees C change.

Lysaght advise roof sheet lengths of up to 24m can be used before an expansion joint is required. An expansion joint is an overlap of 250mm with 15mm clearance.

Translucent sheeting has greater expansion than the steel and will require oversize fixings when the two products are used togther. To incorporate 'clear' corrugated sheet products -
Polycarbonate 'Laserlite Apollo' Thermal Expansion 2.1mm per 3m per 10° C