A roof plan is a construction drawing, a top view of the roof, that sets out the layout of the roof structure: the position of the trusses and rafters, the purlins, the ridge, the valleys and hips, and the wall plates.
Characteristics
A roof plan looks down on the roof from directly above and records where each structural member sits.
- It shows the spacing and position of trusses or rafters.
- It marks the lines of the purlins that run across them.
- It locates the ridge along the top, together with any valleys and hips.
- It indicates the wall plates on which the structure bears.
Because it is drawn to scale, the plan lets the builder read off spacings and dimensions and check that everything lines up before a single timber is cut.
Application
The roof plan is used both to set out the structure on site and to work out the materials needed. From it, a carpenter can count the members, calculate lengths and order timber with confidence. It also serves as a reference during assembly, so that trusses land in the right places and the purlins tie the whole roof together. For more complex roofs, it is often read alongside a roof development drawing, which supplies the true lengths and angles of the sloping surfaces.
Related terms
- Roof structure
- Roof truss
- Roof development drawing
- Working drawing
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