What is an Emy truss?
An Emy truss is a timber arched truss built from thin, bent planks stacked on top of each other and clamped together with bolts and iron bands into a single resilient arch — an early precursor of modern glued laminated timber. The system was developed in 1825 by the French engineering officer Armand-Rose Emy and allowed wide free-spanning roofs in timber.
Construction
An Emy truss consists of:
- A series of thin planks (often 25–50 mm thick) stacked as band lamellae
- A curved shape formed by bending the planks around a former
- Through bolts running across the stack
- Iron bands or stirrups holding the package together
- A tall, slender arch of strikingly light appearance
- Tie rods or floor to absorb the lateral thrust
Unlike modern glued laminated beams (glulam), the Emy truss uses no glue; load transfer relies on mechanical clamping.
Pros and cons
Pros
– Greater span than solid timber
– Lighter than solid timber or metal beams of similar length
– Material- and transport-friendly in the 19th century
– Beautiful open, monumental interior
Cons
– Vulnerable to shear between layers
– Bolts and bands must be re-tensioned regularly
– Susceptible to fire and rot without maintenance
– Now largely replaced by steel and glulam
Application
The Emy truss was widely used in the 19th century for:
- Military riding halls and drill halls
- Railway station roofs in France and Belgium
- Market halls and warehouses
- Church roofs in timber-rich regions
- Drying houses, tobacco and hop sheds
Notable examples include the riding hall of Libourne and various military complexes in French Flanders. From around 1900 wrought and cast iron, then steel, displaced the system.
Comparison
| Truss type | Period | Connection |
|---|---|---|
| Emy truss | 1825–1900 | Bolts and bands, no glue |
| Philibert truss | 1561–1850 | Stacked planks |
| Belgian truss | 19th c. | Mortise-and-tenon timber joint |
| Glulam (glued laminated) | 20th c. | Glue under pressure |
Related terms
- Philibert truss
- Arched truss
- Glued laminated timber
- Belgian truss
- Truss
- Polonceau truss
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