Principles of pitched roof construction

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There are a number of ways to design and construct pitched roofs using timber. Traditionally, builders constructed them on site, cutting and fitting each piece to its neighbours. Following the Second World War, various forms of prefabricated truss were developed, with the intermediate rafters and purlins cut and fitted on site.

Currently, the highly engineered and slender trussed rafter, where the rafters and ceiling joists are triangulated to form a lightweight prefabricated truss, is the most widely used form of domestic roof construction.

This Wood Information Sheet (WIS) covers the general principles of pitched roof design only. It does not cover the design of hatches, chimney openings or the additional support that is required for water tanks or other added loads.



  • Site-constructed roofs
  • Purlin roofs
  • Bolted and connectored trusses
  • Trussed rafter roofs
  • Rooms in the roof
  • Insulation and ventilation
  • Preservative treatments

Suggested Reading

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