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Erection Procedure
 
Assembly of trussed rafter roofs
 
(Information relating to the assembly of trussed rafter components and infill)

Once the trussed rafters have been safely raised to eaves level utilising either the methods or principles outlined previously and assuming that all the necessary information has been forwarded by the Roof Designer to the contractor, then it is possible for the assembly of the trussed rafter roof
construction to commence. In similar fashion to the other work tasks associated with trussed rafter roof construction, the assembly of the roof components should be carried out in strict accordance with a contractor prepared safe working method statement (see section 3.13 for a typical example of a Contractors General Risk Assessment and supporting Method Statement).

Whichever method of raising the trusses is utilised, the principal risks associated with assembling trussed rafter roofs in their final location are either falling, temporary instability and collapse of the partially complete structure or being struck by a falling truss/object. All of these issues need to be addressed to safely proceed with the operation. The manner in which any other residual site hazards should be dealt with should be based on the principle of a hierarchy of risk control. This principle states that the most desirable option is to design out the hazard and subsequent risk completely at the design stage and the least desirable option is to provide
personal protection systems such as restraint harnesses (i.e. protection after a fall).
With regard to assembling trussed rafter roof structures, the most desirable approach for standard storey height construction (up to 3.0m from floor to
ceiling) is to provide both a perimeter working platform externally and either a full or partial working platform internally and erecting the trusses
using the standard erection procedure as shown in figure 94a. Auseful modification to the basic bracing procedure is to rigidly brace the first truss back to the external scaffold to allow roof assembly to proceed unencumbered in a direction away from that first truss.
 
Alternatives to this approach might involve the combination use of working platforms and safety nets or, in situations where the potential fall distances
are sufficient to allow their safe use, the installation of larger nets and/or restraint harnesses.

At all times, the Designers and Contractors should undertake proper Risk Assessments of the tasks in hand and draft appropriate method statements accordingly. Where the trussed rafter designer/manufacturer is also engaged to erect the roof structure then the method statement would be prepared by him and approved by the principal Contractor (who is responsible for the Health and Safety of all personnel, directly employed or otherwise, on the site). Some amendment or reassessment of the proposed working method may be necessary before the Principal Contractor allows the work to commence.