INTRODUCTION
Double fixing brackets can be used to increase the total amount of fixings required to securely attach the SunLock framing system to a roof structure.
This can particularly useful in the following situations:
Where the panels are required to be mounted in landscape (where the large spacing between purlins makes it impossible to provide enough fixings)
Where the installer / designer doesn’t wish to include a separate sub-frame.
Where the installer / designer doesn’t wish to include a third rail per panel row.
This guide covers:
Calculating whether double fixing brackets are required.
Installing the double fixing brackets to the roof.
GUIDE
Calculating whether double fixing brackets are required
In this example, the house is assumed to be:
In wind region B
Have a tin roof with a pitch of 25 degrees
Have timber purlins spaced at 1200mm
Some panels are installed in the end zone (in landscape format)
From the SunLock commercial Flush Assessment Report, it states that the fixings must be a maximum of 746mm apart.
As the purlins are spaced 1200mm apart, there are not enough fixings to run two rails with a single fixing across each purlin. To work out whether double fixing brackets are required:
Calculate panel row length (1000mm x 3 panels = 3000mm)
Divide it by the maximum spacing length (3000mm / 746mm = 4.02)
Round up the answer to get total amount of bays between fixings per rail
(= 5)
Add one to work out the total amount of fixings per rail. (= 6)
As there are only 5 purlins available and a minimum of 6 fixings are required per rail, there are not enough fixings to run two rails with a single fixing across each purlin.
If a double fixing bracket was used the total amount of fixings would be 5 purlins x 2 (double fixing bracket) totalling 10 fixings locations per rail.
As 10 fixings are greater than the required 6, a double fixing will be sufficient.
SLCF3
NOTES
Terrain
Terrain Category 3 (TC 3) denotes terrain with numerous closely spaced obstructions having heights generally from 3m to 10m.
The minimum density of obstructions shall be at least the equivalent of 10 house-size obstructions per hectare.
Terrain Category 2 (TC 2) denotes open terrain, including grassland, with well-scattered obstructions having heights generally from 1.5m to 5m, with no more than two obstructions per hectare.
Refer to AS/NZS1170.2-2011(R2016) Chapter 4.2.1 for Terrain Category definitions.
End Zones
A roof is divided into 3 equal length zones about the long side of the building. The zone boundary lines are perpendicular to the building's length axis line and roof ridge line and parallel to the roof end edge line. The two zones close to the two building ends are defined as End Zone. The middle zone is defined as Central Zone.
Refer to AS/NZS1170.2-2011(R2016) Appendix D6 for Roof Zone notion.
Compliance
Fixing spacing in the above tables are based on 14 gauge penetrative fixing pull-out capacity into 1.9BMT steel and 35mm embeded into JD4 seasoned timber. The fixing spacing must be adjusted if the roof structure being fixed into does not met the minimum requirements. The recommended typical penetrative fixings to be adopted are as following:
Steel purlin/batten - 14g-10TPI Self-drilling Tek Metal Screw (Buildex recommended)
Timber purlin/batten - 14g-10TPI Self-drilling T17s Timber Screw (Buildex recommended)
All self-drilling penetrative fixing must be in compliance with AS3566-2002(R2015).
To ensure the given fixing spacing tables are valid, rail splice connectors must not be installed at the support point or at the middle span point between two adjacent supports. It is recommended to install the connector at 1/4 span points from the supports.
For Further information
For further information contact SunLock on 1300 655 554 or order@sunlock.com.au.