The roofing/walling shall be 0.42 (or 0.48) mm BMT Stramit Longspan^® 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, suitable for minimum corrosivity category 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. All debris (nuts, screws, cuttings, filings etc.) shall be cleaned off daily.

A NATSPEC work section is available for this product. Download

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/714. This is available from Stramit or on the NT BAC website.

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.

All external fastening screws must conform to AS 3566 – suitable for minimum corrosivity category 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 in non-cyclonic areas use:

*For steel less than 1.5mm bmt thickness fastener capacity must be checked.

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

Heavy - 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 conform to AS 1562.1:2018 with 1.1kN load specified in AS/NZS 1170.1:2002 for R2 – Other Roofs. These require minimal careful foot traffic only on the designated footpath. Suggested for use only where occasional aesthetic imperfections from foot traffic are acceptable.

Tables are based on tests to AS 1562.1:2018 and AS 4040 parts 0 and 1.

For more information on foot traffic performance of Stramit's roofing profiles refer to Stramit's Foot Traffic Guide.

Stramit Longspan^® Roof and Wall Cladding is manufactured from hi-tensile G550 colour coated steel, aluminium-zinc-magnesium 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 AS/NZS 2728:2013 – Type 4 and, for the substrate, with AS 1397:2021. Aluminium-zinc-magnesium alloy coated AM100/AM125, Zinc-aluminium alloy coated AZ150 and galvanised Z450 conform to AS 1397:2021.

Stramit has a comprehensive range of colours as standard. Ask your nearest Stramit location for colour availability.

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

(2 degrees is sufficient for Class 1 and 10 buildings.)

The spans shown below take account of 'normal' foot traffic and wind resistance including local pressure zone effects. Pressures are based on AS 4055:2021 or AS/NZS 1170.2:2021.

Where the two standards differ, the worst case has been taken for each classification. Data should only be used for buildings with dimension limits given in AS 4055:2021,7m or less in average height, 16m max width and length less than 5 times the width, where both length and width exceed the building height and site is unaffected by land topography. Maximum roof pitch 35º. Refer to AS 4055:2021 for more detail. 

*Where roof pitch is less than 10 degrees, use spans given in red italics for roof corners, or where roof pitch is greater than or equal to 10 degrees, use spans in red italics at the ridge/edge corners.

# Not suitable for roof corners or ridge ends where pressure higher.

Internal spans must have both end spans 20% shorter. TC – Terrain Category. FS, PS, NS – Full, partial and no shielding. Internal pressure coefficient +0.2/-0.3, external pressure coefficient -0.9 (roof)/ -0.65 (wall). Values are only valid for use with steel members of 1.5mm or thicker. Where thinner supports are used, fastener capacity must be checked. Refer to Stramit® Top Hat & Battens Product Technical Manual for more information. 

For more specific applications Stramit Longspan® cladding must be designed to the pressure and foot traffic limitations below and on the next page. Roof spans may exceed those shown in this table, provided the wind pressure and foot traffic limits are not exceeded. 

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.

*At these radii a maximum support spacing of 1200mm applies, and limit state pressure capacities are reduced by 14% for serviceability and 7% for strength. These reductions apply proportionately up to the lowest neutral radius.

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

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

Stramit Longspan^® Roof and Wall Cladding has a similar water-carrying capacity to most close pitched trapezoidal profiles. This and the decking stiffness enable roof slopes to be as low as 3° 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 1% Annual Exceedance Probability (formerly 100 year ARI) rainfall intensity.

Based on AS 1562.1:2018.

To avoid ponded water, minimum slope of 3º should be maintained along the entire roof length.

Stramit’s Roof Slope Guide provides additional information.

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

Tables are based on testing to AS 1562.1:2018 and AS 4040 parts 0 and 2. Internal spans must have both end spans 20% shorter. Values only valid for use with steel support members of 1.5mm or thicker. Where thinner supports are used, fastener capacity must be checked. For use with battens supports on roofs, refer to Stramit® Top Hat and Batten Product Technical Supplement. Refer to Stramit® Cyclonic Areas Roof and Wall Cladding Brochure for information on use in Cyclonic Regions. 

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.

1. Ensure all purlins are in line and correctly installed and that mesh and blanket (if specified) are in place.
2. Position and fix the first sheet ensuring the correct sheet overhangs (minimum 50mm). Ensure that screws have a weatherproofing seal and are not overtightened to avoid indentations in walls or roofs.
3. 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.
4. Measure the overall cover width at top and bottom of the sheets from time to time to avoid ‘fanning’.
5. For roof spans exceeding 900mm and wall spans exceeding 1200mm, stitch the sidelaps at midspan.
6. Turn up the pans at the upper roof edge, turn down the pan at the lower edge and install flashings. Fix flashings according to AS 1562.1:2018.
7. 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.