The areas of Design Responsibility for the roof structure of a building are as follows:-
1. Trussed Rafter Designer
The Trussed Rafter Designer is responsible for the design of trussed rafters as individual components. He or she must ensure the structural integrity of the trussed rafter units and inform the Roof Designer (or Building Designer where there is no specifically appointed Roof Designer), of any stability requirements needed in the design of the trussed rafters.
2. Roof Designer
If the Building Designer has appointed a Roof Designer, they are responsible for the design of the roof structure as a whole and must inform the Building Designer of all information pertinent to the roof regarding its interaction with the supporting structure and adjacent elements of the building.
If no person is appointed specifically as the Roof Designer it falls upon the Building Designer to undertake the responsibilities of the Roof Designer.
3. Building Designer
On every project it is essential that one person assume overall responsibility as Building Designer. The Building Designer may be the owner of the building, his appointed Architect, a Structural Engineer appointed by the owner or Architect, or the Contractor or Builder.
The Building Designer is responsible for providing the information listed in Section: 1.3 (and in section 11.1 of BS.5268-3) to the trussed rafter designer and for ensuring adequate provision is made for the stability of the individual trussed rafters.
The Building Designer is responsible for detailing all elements of bracing required in the roof, including that necessary to provide the lateral restraints to truss members required by the Trussed Rafter Designer.
The Building Designer is also responsible for detailing suitable fixings for both the trussed rafters and the wall plates to provide the restraint against uplift required by the Trussed Rafter Designer.