What is an A-frame truss?
An A-frame truss is a simple roof construction in the shape of the letter A, consisting of two sloping rafters that meet at the top and are connected at the bottom by a horizontal tie beam. It is the most basic truss form and serves as the foundation for many roof types.
How is an A-frame truss constructed?
An A-frame truss consists of three main elements:
- Two rafters (truss legs) — the sloping beams that form the roof slopes
- A tie beam (bottom chord) — the horizontal beam connecting the rafters at the bottom, preventing the walls from being pushed outward
- Optionally a collar beam — an additional horizontal connection higher in the truss for extra rigidity
The triangular shape makes the A-frame truss inherently stable: a triangle cannot deform without one of its sides breaking or bending.
Application
The A-frame truss is commonly used for:
- Sheds and outbuildings — spans up to approximately 6-8 metres
- Garden buildings and carports — simple structures with a gable roof
- Garages — standard roof construction for detached garages
- Small houses — traditional roof constructions
For larger spans (over 8 metres), the A-frame truss is often supplemented with struts or replaced by a lattice truss.
A-frame vs. other truss types
| Truss type | Span | Complexity |
|---|---|---|
| A-frame truss | Up to 6-8 m | Simple |
| Lattice truss | 10-20 m | Medium |
| Scissor truss | Up to 10 m | Medium |
| W-truss (prefab) | Up to 12 m | Factory |
Related terms
- Truss
- Rafter
- Collar beam
- Roof structure
- Gable roof
Learn more about building terms in our knowledge base at fredsdiyplans.com.