What is an English truss?
An English truss is a timber or steel lattice truss with a triangular overall shape, in which vertical and diagonal members divide the interior. It is an efficient truss for medium to large spans and is used in industrial halls, churches, barns and farmhouses.
Composition
An English truss consists of:
- Top chords (rafters) — two members following the roof slope (round timber, sawn timber or steel profile)
- Bottom chord (tie beam) — horizontal member that absorbs the lateral thrust
- Verticals (posts) — vertical members dividing the top into bays
- Diagonals — angled members that transmit compression and tension
- Connection nodes — usually with bolts, gusset plates or welded joints
The lattice subdivision keeps the individual members short so they will not buckle under load.
Applications
Suitable for
- Spans — typically 6 to 20 metres, in steel up to 40 metres
- Industrial halls — simple spans with light roofing
- Farm barns — grain storage, machinery sheds
- Churches and gymnasiums — as exposed timber roof structures
- Station halls and 19th-century factories — historical examples
Materials
- Timber — common for medium spans up to about 18 m
- Steel — for larger spans and heavy loads
- Glulam — modern variant for representative halls
- Composites — for special applications
History
Lattice trusses — including the English truss — were further developed in the 19th century to allow large spans for railway stations, factories and churches. The truss is named after the English industrial building tradition, although similar systems arose independently in several countries.
Variants
The English truss is related to other lattice types:
- Polonceau truss — uses tie rods and compression struts
- Dutch truss — diagonals run from the ridge to the centre
- Belgian truss — only diagonals, no verticals
- Fink truss — American variant
- Howe truss — diagonals in compression, verticals in tension
- Pratt truss — opposite diagonal direction
Pros and cons
Advantages:
- Light structure compared with solid beams
- Good material utilisation
- Easy to prefabricate in elements
Disadvantages:
- Many connections required
- Joint maintenance for timber
- Less suitable for heavy concentrated loads
Related terms
- Lattice truss
- Polonceau truss
- Dutch truss
- Belgian truss
- Roof structure
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