Pitched roofs

7.2.2Provision of information

Designs and specifications shall be produced in a clearly understandable format, include all relevant information and be distributed to the appropriate personnel.

Designs and specifications should be issued to site supervisors, relevant specialist subcontractors and suppliers, and include the following information:

  • The layout of trusses and associated items
  • Details of mono-pitch, lean-to roofs and roof intersections (i.e. hips and valleys)
  • Details of girder trusses, multiple trusses and diminishing trusses, including how they are to be fixed together and supported on truss shoes, layboards or similar
  • Details of bracing requirements
  • Details of supports for equipment in the roof space
  • The type and position of vapour control layers
  • Details of restraint/holding-down strapping, including coatings and fixings
  • The position and thickness of insulation
  • The means of providing eaves ventilation
  • Details of firestopping at separating wall and boxed eaves
  • Details of coverings and fixings, including number and type
  • Details of flashing details at abutments, chimneys, etc
  • Details of trimming around chimneys, access hatches, etc.

For trusses, the design should be provided to the manufacturer in accordance with PD 6693-1, which includes:

  • usage, height and location of building, referencing any unusual wind conditions
  • rafter profile, referencing camber where required
  • spacing, span and pitches
  • method of support and position of supports
  • type and weight of coverings, including sarking, insulation and ceiling materials
  • eaves overhang and other eaves details
  • size and approximate position of water tanks or other equipment to be supported
  • positions and dimensions of hatches, chimneys and other openings
  • type of preservative treatment, where required
  • special timber sizes, where required to match existing construction.