Working at heights and roof construction in South Australia

Roof construction and fall protection

Under the WH&S Act & Regulations, a PCBU (including a sub-contractor) is required to manage risks to health & safety associated with a fall by a person from one level to another that is reasonably likely to cause injury.  

Prior to the commencement of an activity that includes working at heights, such as the erection of roof framing or placement of sheet roofing material, the PCBU in conjunction with workers should undertake a risk assessment. If the work involves a risk of a person falling more than 3 metres, a Safe Work Method Statement must be documented outlining the safe working procedures.

When constructing a conventional roof where ceiling joists are erected prior to pitching the rafters, the placement of the ridge beam, and the fixing of rafters, may be done from planks or other platforms on the ceiling joists. Where ceiling joists are not erected, a work platform will need to be provided for framers to work from. The use of planks (2 wide) could be considered as a temporary work platform.

Framers working at the external wall must not work closer than 1.2m to the external wall unless some means of fall protection is in place. 

The fixing of trusses, ceiling joists or rafters at the perimeter of the building, may be carried out from external scaffolding or trestle scaffolds set up internally or from ladders. If work is carried out near window/door openings an additional higher level guard rail may be necessary, particularly for buildings exceeding one storey in height.

Erecting roof trusses

At no time should a person work closer than 1.2m to an external wall, stand on or work from, an external top plate without suitable fall protection.

When trusses are erected at 600m centres, competent persons working between the trusses to fix or brace them can use the erected trusses as a form of fall protection. Where trusses exceed 600mm centres and an intermediate ceiling joist has been installed the combined bottom chord of the truss and ceiling joist may be used as a work platform, subject to the intermediate ceiling joist being securely fixed to the hanger beams at the required ceiling joist spans, and permanent spacers are in place along the top chords.

* Image sourced from Model Code of Practice Managing the Risk of Falls in Housing Construction

Truss bottom chords are considered a safe working area for a competent person if all the below conditions are met

The erection of roof trusses may be undertaken by competent persons from internal top wall plates or from scaffold planks supported on internal wall frames provided:

• the bottom chords and intermediate ceiling joists have been visually checked for defects,
• no person is exposed to the risk of a fall into a stairwell or void,
• work platforms are adequately supported across their spans,
• timber waling plates & vertical struts (not less than 70x35 F5) may be used to support temporary work platforms or planks to reach the apex of trusses when fixing braces etc.    
• a Safe Work Method Statement (SWMS) has been prepared and signed off by the workers involved where the fall heights exceed 3m.

Fixing of roof battens/purlins

The process for installation of roof battens/purlins depends on the roofing material. Although there are similarities in the methods used to install metal and tile roofing, there are also differences. 

In all cases roof battens need to be capable of supporting the expected loadings from installers. In addition to external fall prevention, or framers not working closer than 1.2m to the external wall: 

• Roof trusses should be installed and secured at spacings not exceeding 600 mm centres, with batten spacings not exceeding 900 mm centres.
• Where roof trusses are installed and secured at spacings greater than 600 mm but not exceeding 900 mm centres, batten spacing should not exceed 450 mm centres.
• Where roof truss spacing exceeds 900 mm centres (e.g. 1200 mm) and manufacturers’/suppliers’ instructions permit, intermediate battens should not exceed 450 mm centres. They should also be installed sequentially and in a manner that controls the risk to installers (i.e. install the battens at the eaves first and then work up the roof plane to provide a barrier against falling between the truss rafters), otherwise other fall protection must be used.

Where ceiling or roof framing members exceed the recommended spacing as set out above, such as Class 10 type structures (pergolas/carports/garages), all roof framing and the fixing of roof coverings must be carried out with the aid of safety systems as set out in WH&S Regulation 79.

The table below provides examples of the matters that could be considered in undertaking a risk assessment prior to commencement of the daily activities surround the erection of roof framing. 

Matters to be considered before proceeding with roof frame construction

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