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  • Cost-effective to use and easy to install
  • Architectural flexibility accommodates curved roofs and roof pitches as low as 3 degrees
  • Variable fixing screw patterns give design flexibility
  • Suitable for wall cladding
  • .42 & .48 thickness available
  • Available in an extensive range of colours, Colorbond® Steel, UniCote® & Mangaflow®
  • Colorbond® Steel
  • Unicote
  • MagnaFlow

Armour Grey®

Armour Grey®

Armour Grey®

Technical Information
Architectural Specification

The roofing/walling shall be 0.42 (or 0.48) mm BMT Stramit Longspan® Roof and Wall Cladding in continuous lengths with trapezoidal ribs 27mm high, spaced at 100mm centres. Sheeting material shall be protected steel sheet to Australian Standard AS1397, with a minimum yield stress of 550MPa (Grade G550) and an AM100/AZ150 coating with an oven-baked paint film of selected colour, or a plain AM125/AZ150 coating.

The sheeting shall be fixed to the purlins/girts in accordance with the manufacturer’s recommendations. Suitable fixing screws in accordance with Australian Standard AS3566, Class 3, shall be used at every support with side lap fasteners installed at mid span if required. Sheets shall be laid in such a manner that the approved side lap faces away from the prevailing weather.

A minimum of 50mm shall be provided for projection into gutters. Flashings shall be supplied in compatible materials as specified; minimum cover of flashing shall be 150mm. All sheeting shall be fixed in a workman-like manner, leaving the job clean and weathertight. Repair minor blemishes with touch-up paint supplied by the sheeting manufacturer. All debris (nuts, screws, cuttings, filings etc.) shall be cleaned off daily.

Class 4 fasteners should be used <1km from the coast.

Cyclonic areas

Cyclonic data for Stramit Longspan® Roof and Wall Cladding can be found in the Stramit Cyclonic Areas Guide. Information on the use of Stramit Longspan® Roof and Wall Cladding in the Darwin area can also be found in deemed-to-comply sheets No M/147/01. This is available from Stramit or on the NT BAC website.

Fastener Locations

Stramit Longspan® Roof and Wall Cladding can be fixed with either 3, 4 or 5 fasteners per sheet at each batten/purlin to meet the required performance values.

Fastener Locations

All external fastening screws must conform to AS3566 – Class 3. They are to be hexagon headed and must be used with sealing washers for both roofing and walling.

For connecting to purlins or top hats use:

Foot Traffic

Foot traffic limits for Stramit Longspan® Roof and Wall Cladding are shown for 3 alternative foot traffic categories:

High Maintenance - for applications with repeated maintenance, particularly where personnel may be unfamiliar with correct procedures for walking on metal roofs.

Normal - based on traditional expectations, with moderate maintenance foot traffic using designated footpaths

Controlled - spans that confirm to AS1562 but require minimal careful foot traffic only on the designated footpath.

Suggested for use only where occasional aesthetic imperfections from foot traffic are acceptable.

Foot Traffic

For more information on foot traffic performance of Stramit's roofing profiles refer to Stramit's Foot Traffic Guide where tables are based on tests to AS1562 and AS4040 parts 0 and 1.

Materials and Sheet Mass

Stramit Longspan® Roof and Wall Cladding is manufactured from G550 colour coated steel or zinc-aluminium alloy coated steel. In some locations galvanised and severe environment colour coated steel may be available by arrangement.

Colour coated steels are in accordance with AS2728 – Category 3 and, for the substrate, with AS1397. Zinc-aluminium alloy coated AZ150, aluminium-zinc-magnesium alloy coated AM100/AM125 and galvanised Z450 conform to AS1397.

Materials and Sheet Mass
Minimum Roof Slope

The minimum roof slope for Stramit® Longspan Roof and Wall Cladding is 3 degrees (1 in 20).


The spans shown below take account of normal foot traffic and wind resistance including local pressure zone effects. Pressures are based on AS4055 or AS1170.2.

Where the two standards differ, the worst case has been taken for each classification. Data should only be used for buildings 7m or less in height, 1000m2 or less in area and unaffected by land topography.

Spring Curving

Stramit Longspan® Roof and Wall Cladding can be spring-curved, concave and convex, including curved ridges, provided it is sealed at the apex, and within the recommended limits.

Spring Curving

The Stramit Spring Curving Guide has more detailed information.

Thermal Expansion

All metal roof sheeting is subject to thermal expansion and this needs to be accommodated where there is a temperature difference between the sheeting and the structure.

The colour of the sheeting will affect the amount of thermal expansion, and whether the sheet is flat or cured will affect its ability to resist without problems. Sheet lengths should be limited as follows.

Thermal Expansion
Water Capicity

Stramit Longspan® Roof and Wall Cladding has a superior water-carrying capacity, to most close pitched trapezoidal profiles. This and the decking stiffness enable roof slopes to be as low as 3.0° for many applications.

Roof run lengths are the combined lengths of all roof elements contributing to a single pan drainage path. This can include the roof length upstream of a roof penetration that concentrates flow into other pans.

The table below gives slopes for 100 year return period rainfall intensity.

Water Capicity
Wind Pressures

Derived from testing, the following tables give the wind load resistance for both serviceability and strength limit states.

Wind Pressures Wind Pressures
Installation Information

Stramit's cladding can be easily cut, where required, using a power saw with a cold cut saw blade or a power nibbler and, for localised cutting, tin snips. Avoid the use of abrasive discs as these can cause burred edges and coating damage. Please dispose of any off-cuts carefully and thoughtfully.


Stramit Longspan® cladding is readily installed with or without fibreglass insulation blanket. If practical lay sheets in the opposite direction to prevailing weather.

Installation of Stramit Longspan® cladding is a straightforward procedure using the following fixing sequence.

  • Ensure all purlins are in line and correctly installed and that mesh and blanket (if specified) are in place.
  • Position and fix the first sheet ensuring the correct sheet overhangs (minimum 50mm). Ensure that screws are not overtightened.
  • Continue to fix subsequent sheets checking that sheet ends at the lower edge are exactly aligned. It is important that the underlap of one sheet does not protrude beyond the overlap of the next – if this is unavoidable, the underlap must be trimmed locally or water ‘drawback’ may occur.
  • Measure the overall cover width at top and bottom of the sheets from time to time to avoid ‘fanning’.
  • For roof spans exceeding 900mm and wall spans exceeding 1200mm, stitch the sidelaps at midspan.
  • Turn up the pans at the upper roof edge, turn down the pan at the lower edge and install flashings.
  • Clean up the roof after each days work, removing all screws, cuttings, swarf etc, and leave roof clean and watertight.

As with all roofing products, we recommend extra caution be taken when walking on the roof. When walking on Stramit Longspan® Roof and Wall Cladding, always wear flat rubber soled shoes and place feet only on the ribs, taking care to avoid the last rib or two near edges of the metal roof area.

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