Stramit Snaptite Concealed Fixed Decking

Applications

The visual appeal, strength, wide cover, light weight and weather resistance of Stramit Snaptite™ decking make it perfect for all commercial roofing applications.  Its excellent strength and ease of assembly allow for long, economical spans.  The large water-carrying capacity and weather-tightness permit very low roof pitches, leading to economies in the building structure. 

Stramit Snaptite™ decking may also be used for domestic applications.

Materials

StramitSnaptite™ cladding is manufactured from colour coated steel or zinc-aluminium 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 and galvanised Z450 conform to AS1397. 

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

STRAMIT SNAPTITE™ DECKING - DECKING MASS (kg/m2 of roof area)  thickness BMT Zincalume® Colorbond® Galvanised® 0.48mm G300 5.97 6.06 6.42 0.55mm G300 6.80 6.89 7.25

Adverse Conditions

Stramit Snaptite™ cladding will give excellent durability in almost all locations. With all of its fastenings protected beneath the decking, Stramit Snaptite™  decking can be expected to outlast through-fixed roofing.  It is however important to choose the correct coating for each application environment. 

The table below shows the suitability of coating types for different exposure conditions. 

suitability of coating type site exposure condition benign moderate severe very severe Zincalume® AZ150 ? ? Galvanised Z450 ? Colorbond® ? Colorbond® Ultra N/A N/A ?

? Question marks indicate conditions where durability may be diminished, depending on the particular application.

The approximate site exposure conditions in the table above are defined below.

site exposure condition distance of site from rough active surf calm, still salt water industrial emission fossil fuel combustion benign 1000m + 100m + 500m + 500m + moderate 400m-1000m 0-100m 250m-500m 250m-500m severe 100m-400m N/A 100m-250m 100m-250m very severe 0-100m N/A 0-100m 0-100m

The suitability and exposure tables above are guidelines only; conditions will vary from site to site. If in any doubt about the choice of coating for a particular application consult your nearest Stramit office for advice.

Compatibility

All building products need to be checked for compatibility with adjacent materials.  These checks need to be for both direct contact between materials, and where water runs from one material to another.  The following guidelines generally avoid material incompatibility:

• For zinc-aluminium alloy coated steel, colour coated steel and galvanised steel roofs avoid copper, lead, green or treated timber, stainless steel and mortar or concrete.
• In addition galvanised steel roofs should not receive drainage from aluminium or any inert materials, such as plastics, glass, glazed tiles, colour coated and zinc-aluminium alloy steel.  Contact Stramit for more detailed information.

Testing

Stramit has in-house, purpose built, testing equipment used to design, develop and improve products for the Australian market.  In addition many Stramit products are tested or witnessed by independent organisations.  These include:

• Cyclone Testing Station
  (James Cook University)
• The University of Sydney
• Monash University
• CSIRO
• University of Technology, Sydney

This ongoing research and development activity ensures that Stramit remains at the forefront of innovation, design and consumer information.

Architectural Specification

This specification can be found on the Stramit web site and can be easily downloaded onto your documentation.

The roofing/walling shall be 0.48 (or 0.55) mm BMT Stramit Snaptite™ decking, in continuous lengths with trapezoidal ribs 48mm high, spaced at 203mm centres.  Sheeting material shall be protected steel sheet to AS1397 with a minimum yield stress of 300MPa (Grade G300) and an AZ150 zinc-aluminium coating with or without an oven baked paint film of selected colour.  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 rib at every support.  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 roof manufacturer.  All debris (nuts, screws, cuttings, filings, etc) shall be cleaned off daily.

Spans

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 section 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.  
    


Please refer to page 4 of the Stramit Snaptite™ Product Technical Manual for Maximum Span Chart (mm), Serviceability Limit State Capacity and Strength Limit State Capacity (Non-Cyclonic) Tables.

Foot Traffic

Foot traffic limits for Stramit Snaptite™ decking are shown for three alternate foot traffic categories. These are:

• 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 foot paths.
• Controlled – spans that conform to AS1562 but require minimal careful foot traffic only on the designated foot path. Suggested for use only where occasional aesthetic imperfections from foot traffic are acceptable.

STRAMIT SNAPTITE™ DECKING – FOOT TRAFFIC LIMITED SPANS (mm) thickness bmt fasteners per sheet span type foot traffic limits heavy normal controlled     internal - 1000 1200 0.48 2 equal - 800 900     double - 800 900     internal - 1900 2100 0.55 2 equal - 1500 1700     double - 1500 1700 Tables are based on tests to AS1562 and AS4040 parts 0 and 1

For more information on foot traffic performance of Stramit Snaptite^TM decking and other Stramit^®roofing profiles refer to Stramit’s Foot Traffic Guide.                  

Spring Curving

Stramit Snaptite™decking can be spring-curved, concave and convex, including curved ridges, provided it is within the recommended limits below: 

STRAMIT SNAPTITE™ DECKING – SPRING-CURVED RADII LIMITS (m)   performance restricted restricted by drainage at the rainfall intensities shown bmt (mm) minimum* radius lowest neutral radius 370 mm/hr 220 mm/hr 150 mm/hr 0.48 No data available 0.55 50* 142 280 474 >500 *At these radii a maximum support spacing of 900mm 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.

For more comprehensive information on spring curving Stramit Snaptite™ decking and other Stramit^®roofing profiles refer to the Stramit Spring Curving Guide.

Designing for Snow

Concealed fixed decking such as Stramit Snaptite™ decking is the preferred roofing material in alpine areas.  This, and many other design suggestions, can be found in Australian Standards HB 106 - 'Guidelines for Design of Structures in Snow Areas'.  Particular attention is drawn to maintaining an adequate roof slope for snow shedding, and screw fixing of deck pans beneath the ridge capping. 

Downward load capacities for Stramit Snaptite™ decking have not been tabulated, but can be assumed to equal the outward capacities shown.

Thermal Expansion 

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. 

Stramit Snaptite™decking has excellent resistance to the problems associated with thermal expansion.  Nevertheless sheet lengths should be limited to those shown below. 

STRAMIT SNAPTITE™ DECKING - MAXIMUM SHEET LENGTH (m) roof colour light dark Flat 35m 25m Spring-curved 30m  20m

Significant failures of pierced fixed roofing have occurred on commercial buildings where dimensional changes from thermal expansion have not been accurately incorporated in the roof design.  These can result in elongation of fastener penetrations, consequent water leaks, fastener failure and unacceptable frictional noise.  Through-fixed profiles which incorporate special sealing may exacerbate these problems.

Water Carrying

Stramit Snaptite™decking has excellent water-carrying capacity. This and the decking stiffness enable roof slopes to be as low as one degree 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. 

STRAMIT SNAPTITE™ CLADDING – MINIMUM ROOF SLOPE (degrees) Rainfall Intensity mm/hr total roof run length (m) 50 60 70 80 90 100 110 120 130 140 150 150               1.0 175 Minimum               1.0 1.2 200 Slope 1°           1.0 1.1 1.4 1.7 225           1.0 1.3 1.7 2.0 2.5 250           1.0 1.4 1.8 2.4 2.8 3.4 275         1.0 1.4 1.8 2.3 2.8 3.5 4.1 300       1.0 1.3 1.7 2.4 2.9 3.6 4.3 5.0 325     1.0 1.1 1.6 2.2 2.8 3.6 4.3 5.1 6.0 350     1.0 1.4 2.0 2.7 3.5 4.2 5.1 6.0 7.0 375   1.0 1.2 1.7 2.5 3.2 4.1 4.9 6.0 7.0 8.3 400   1.0 1.4 2.1 2.8 3.7 4.7 5.6 6.8 8.0 9.5

For more information on water carrying performance of Stramit Snaptite™ decking and other Stramit^® roofing profiles refer to Stramit’s Roof Slope Guide.

Maximum water protection is also ensured by the absence of faster penetrations when using Stramit Snaptite™ decking.

Fasteners

All fastening screws must conform to AS3566 – Class 3. For connecting to purlins use: 

- No.12 x 30mm hex-head self-drilling and threading screws (available pre-loaded into clips in some locations)

	- No. 12 x 50mm hex-head type 17 self-drilliing screws
	- 40mm/60mm drive nails

Accessories

Use only the correct, authentic, Stramit accessories: 

- supplied with or without nails

Installation

Stramit Snaptite™ decking is readily installed with or without fibreglass insulation blanket. If practical lay sheets in the opposite direction to prevailing weather. 

Installation of Stramit Snaptite™ decking is a straightforward procedure using the following fixing sequence:

• Ensure all purlins are in line and correctly installed.  Using a string line or the edge of the first sheet, align the first row of fixing clips.  Screw the clips to the purlins with the arrow in the direction of laying.
• Locate the first sheet over the clips with the correct projection at each end of the sheet.  Snap each rib on to the clip at every purlin.
• Place next clip over trailing edge of the first sheet, then fasten clip to purlin as before.

• Continue to lay sheets as before.  From time to time measure coverage of sheets at ridge and eaves to maintain squareness. 
• At end of purlin cut fixing clip (and, if necessary, the roof sheet) to suit.
• Turn up ends of sheet at ridge and turn down the eaves ends into gutters using the Stramit Snaptite^TM decking turn up/down tool.
• Secure leading and trailing edge of the roof with a full or cut-back clip, or sealed fasteners through the roof tray, at every purlin.  Cover these with side flashings.  Install all flashings as required to weatherproof and complete the roof.
• Clean the roof after each days work, removing all screws, cuttings, swarf etc, and leave roof clean and watertight.  Repair any minor blemishes in Colorbond finish with Stramit supplied touch-up paint.

Insulation

Blanket up to 50mm in thickness can be readily used.

Walking

As with all roofing products, we recommend extra caution be taken when walking on the roof. When walking on Stramit Snaptite™ decking roofing always wear flat rubber soled shoes and place feet only in the pans, taking care to avoid the last pan or two near edges of the metal roof area. 

Good Practice

Stramit recommends that good trade practice be followed when using this product, such as that found in Australian Standards Handbook HB39.

Cutting

Stramit Snaptite™ decking can be easily cut, where required, using a power saw with a steel cutting 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.

Prices

Prices on Stramit Snaptite™ decking and its accessories can be obtained from your nearest Stramit location or distributor of Stramit products. As Stramit does not provide an installation service, ask your tradesperson for a supply and fix price. Contact your nearest Stramit location for the names of tradespersons in your area.

Related Products

	Ridge Capping – standard or custom dimensions
	Flashings – a range of custom flashings
Use only where sealing is preferred to ventilation
	Insulation & roofing mesh – a range of mesh, sisalation, plain & foil backed blanket
	Translucent sheeting – fibreglass sheeting in a range of shades and densities

Length

Stramit Snaptite™ decking is supplied cut-to-length. When designing or transporting long products ensure that the length is within the limit of the local Transport Authority regulations. The manufacturing tolerance on the length of product supplied is +0, -15mm.

Ordering

Stramit Snaptite™ decking can be ordered directly, through distributors, or supplied and fixed from the roofing contractor.

Delivery/Unloading

Delivery can normally be made within 48 hours, subject to the delivery location, quantity and material availability, or can be at a pre-arranged date and time. Please ensure that suitable arrangements have been made for truck unloading, as this is the responsibility of the receiver. Pack mass may be up to one tonne. When lifting Stramit Snaptite™ decking, care should be taken to ensure that the load is spread to prevent damage.

Handling/Storage

Stramit Snaptite™ decking should be handled with care at all times to preserve the product capabilities and quality of the finish. Packs should always be kept dry and stored above ground level while on site. If the sheets have become wet, they should be separated, wiped and placed in the open to promote drying.

Maintenance

Exterior surfaces of metal products unwashed by rain can benefit from occasional washing to remove build-up of corrosive salts. Walls beneath eaves or awnings are such a situation. 

Further Information

As well as our standard range of Technical Manuals, Installation Leaflets, Case Studies and other promotional literature Stramit has a series of Guides to aid design.  These include:     

• Concealed Fixing Decking
• Roof Slope Guide
• Foot Traffic Guide
• Bullnosing, Curving and Crimping
• Acoustic Panels
• Cyclonic Areas
• Spring Curving Guide 

Please contact your nearest Stramit location, or visit www.stramit.com.auto download this or any other Stramit literature.

Other Products

Stramit offers a wide range of building products, including     

• Purlins and girts
• Formwork decking
• Roof and wall sheeting
• Lightweight structural sections
• Truss components
• Gutters and downpipes
• Fascias
• Insulating products
• Fasteners   

References

In preparing this document reference has been made to:     

• BlueScope Steel – Technical Bulletin TB-4
  (Maintenance of Colorbond prepainted steel roofing)

• BlueScope Steel – Technical Bulletin TB-1
  (Steel roofing and walling products – selection guide)

• Standards Australia Handbook – HB39
  (Installation code for metal roof and wall cladding)

• Standards Australia Handbook - HB106
  (Guidelines for the design of structures in snow areas)

Product Availability 

Y - Yes     N - No     S - Subject to project size