What is a roof frame?
A roof frame is the complete load-bearing skeleton of a roof, consisting of trusses, purlins, rafters, and all the connections between them. It is the structure that gives the roof its shape and transfers the weight of the roofing material, wind, and snow to the walls or columns.
Roof frame vs. truss — what is the difference?
These terms are often used interchangeably, but there is a difference:
- Truss — A single triangular or A-shaped frame
- Roof frame — The entire system of all trusses plus the purlins, rafters, and connections that together form the roof
A roof frame therefore consists of multiple trusses, connected by purlins.
Components of a roof frame
| Component | Function |
|---|---|
| Trusses | The A-shaped frames that bear the weight |
| Ridge purlin | The horizontal beam at the highest point |
| Wall plate | The beam on the wall on which the rafters rest |
| Purlins | Horizontal beams between ridge and wall plate |
| Rafters | Sloping beams from ridge to wall plate (carry the roofing material) |
| Collar tie | Horizontal beam connecting two rafters (prevents sagging) |
| Braces | Diagonal supports for extra stability |
Types of roof frame
The shape of the roof frame determines the type of roof:
Gable roof
Two sloping surfaces meeting at the ridge. The most common roof frame for houses, sheds, and garages. Simple to construct and drains well.
Mono-pitch roof
A single sloping surface. The roof frame is simpler: rafters from high to low, without a ridge. Widely used for extensions and modern garden houses.
Hipped roof
A gable roof with sloping surfaces on the short sides as well. More complex roof frame with additional hip rafters.
Flat roof
Technically not a roof frame but a flat roof structure with beams carrying the roof sheathing. Always with a slight slope for water drainage.
Roof frame for self-build projects
When building a shed, garden house, or garage, the roof frame is one of the most important components. The most common choices:
- Shed — Usually a gable roof with simple trusses. For small sheds (up to 4 m wide), you can work without trusses using only rafters on the purlins.
- Garden house — Gable roof or mono-pitch roof. For an insulated garden house, you need to account for vapour barrier and ventilation in the roof frame.
- Garage — Often a gable roof with a steeper pitch (30-45°) if you want to use roof tiles. The truss spacing is usually 60-100 cm centre-to-centre.
Building a roof frame yourself
For a simple structure (shed, garden house), you can build the roof frame yourself:
- Calculate the roof pitch — Depending on the roofing material (30-45° for tiles, 3-5° for EPDM)
- Determine the truss spacing — Usually 60 cm centre-to-centre for light roofing, 100 cm for heavier
- Make the trusses — Cut the rafters to size and connect them with a collar tie
- Install the wall plate — Secure to the top of the wall
- Mount the trusses — Place them on the wall plate and connect with the ridge purlin
- Check — Verify everything is level and square before applying the roofing material
Related terms
- Truss
- Purlins
- Ridge purlin
- Wall plate
- Rafter
- Gable roof
- Mono-pitch roof