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Roof construction and working at heights in SA

The information below sets out detailed information about the construction of roof framing and meeting the relevant obligations for safe work in South Australia under the Work Health & Safety Act 2012.

Note that additional information on the construction of roof framing and meeting the relevant obligations for safe work under the Work Health & Safety Act 2012 is contained in the HIA’s ‘Working at heights (SA)’ resource.

Roof construction and fall protection 

Under the WH&S Act & Regulations, a person conducting a business or undertaking (PCBU) 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 must undertake a risk assessment and prepare a Safe Work Method Statement (SWMS) outlining the safe working procedures. 

For timber roofs, AS 1684 Residential timber-framed construction (commonly known as the Timber Framing Code) outlines that ceiling joists may only be used to support construction loads, or the loads from workers, once the ceiling joists are adequately fixed and laterally supported. Fixings to hanging or strutting/hanging beams would be considered necessary. The use of planks (two wide) could be considered as a temporary work platform. Single scaffold planks are only acceptable for work platforms where the fall height does not exceed two metres. 

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. 

Framers working at the external wall exceeding the three metre fall height 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 from trestle scaffolds 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, or stand on or work from an external top plate where the fall height exceeds three metres without suitable fall protection. 

When trusses are erected at 600mm 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. 

Roof construction and working at heights
Figure 1 – NO GO ZONE for persons erecting trusses

Truss bottom chords are considered a safe working area for a competent person if all the below conditions are met (source: NSW Erection of Timber Roof Trusses Industry Safety Standard April 2007).

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 and 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. 
  • an SWMS has been prepared and signed off by the workers involved where the fall heights exceed three metres. 

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 (more than three metres) or framers not working closer than 1.2m to the external wall, ceiling joist, rafters/trusses or battens should be spaced to minimise the risk of internal falls as follows: 

  • Where ceiling joists, rafters and roof trusses are installed at 600mm spacing, the batten/purlin spacing should not exceed 1200mm centres for sheet roofing and 330mm centres for tiles, or 
  • Where ceiling framing is installed at spacing not exceeding 600mm centres and roof trusses and rafters are installed at spacing greater than 600mm, but not exceeding 1200mm centres, the batten/purlin spacing should not exceed 900mm and at a point commencing two metres above ceiling framing, an additional fall protection device such as a 20mm metal top hat batten shall be installed between the battens/purlins (maximum 450mm centres), or 
  • Alternatively 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
Item Yes No Comments
Has the work site Risk Assessment process been completed today for all significant hazards affecting the roof frame erection?    
Have plant and equipment been checked for safe use? e.g. tools tagged & tested, scaffolding, ladders, fall protection, exclusion and clear zones.    
Have all foreseeable risks associated with falls been addressed before work commences, including stair voids, additional noggings in high-level windows, temporary hand rails to upper level balconies, and the like?      
Is the appropriate PPE available for workers?      
Are wall frames suitably fixed and braced?      
Has the ceiling frame or bottom chord of trusses been checked by a competent person before any person walks or works from the framing?      
If required is the crane suitable for the task, and the driver’s qualifications checked?      
Has the SWSM been prepared and signed by all workers, and supplied to the Principal Contractor as required?      
Are workers working at height within the roof frame maintaining the 1.2m ‘no go zones’?      
As the erection of roof trusses proceeds have the temporary/ permanent braces been fixed into position?      

To find out more, contact HIA’s Building Services team.

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