|
Structure
AS6 sheets are designed to be supported by and fixed to steel or timber purlins. Steelwork for AS6 sheets should be within the tolerances given in BS 5950:2 1992: fixing planes on adjacent purlins should be less than L/600 apart (where L is the purlin spacing).
All AS6 sheets are suitable for spanning purlins at 1.8m centres. Consult Steadmans Technical Department for guidance on using the panels on purlins at centres greater than 1.8m. AS6 sheets should be isolated from preservative treated timber purlins by PVC barrier tape applied to the bearing face of the purlins.
Fixings
When fixing AS6 on roof slopes up to 30° (double skin up to 15°) we recommend the use of topfix fasteners from SFS Stadler Limited. These fasteners provide a quick and effective one step fixing operation. However, they must be installed using the recommended depth locating power tool to prevent under or over tightening, which can damage the roof sheets.
When topfix fasteners are not used, the recommended fastener diameter is 8mm, which requires a clearance hole of 8mm + 2mm = 10mm. If using drive screws, the holes should be located centrally on the timber purlins; for hook bolts or similar the hole should be located 4mm upslope from the back edge of the purlin. 6mm diameter fasteners can be used for AS3.
Note
In all instances the Sela washers and protective caps manufactured by SFS Stadler Ltd should be utilised to ensure adequate weather protection.
Checking the topfix fasteners for tightness
Steadmans stock a range of fixings for their fibre cement products. Hook and crook bolts are commonly used to secure the sheets. Clearance holes 4mm larger than the fixing should be pre-drilled to accept the fixing. The appropriate washer must be used to seal the operation.
For normal exposure conditions AS6 should always be fixed with two fasteners per sheet per purlin: consult Steadmans Technical Department for guidance on abnormal conditions.
Overhangs
Sufficient overhangs must be allowed at the eaves to ensure that rainwater discharges into the gutter. Verges must be overhung by one complete corrugation unless a bargeboard is used.
Side Laps
Sealing
Where appropriate, 8mm diameter butyl strips should be positioned as shown.
 |
 |
AS3 profile sealing side lap sealing |
AS6/Firesmart profile side lap sealing |
End Laps
The minimum end lap for either AS3 or AS6/Farmscape is 150mm, fixed as shown in the section below.
Where double sealing is necessary, the second butyl strip should be positioned 100 - 200mm below the fixing.
Drainage
AS6 sheets are intended for roofs with a minimum slope of 5º: if the roof includes rooflights the minimum slope is 6°. Gutters and downpipes should be designed to collect rain and snow falling on the roof and discharge it safely. Drainage capacity should be determined according to BS EN 12056-3:2000.
See 'Flashings & Gutters' in the Product Range section for more details on Steadmans range of drainage accessories.
|
