TR26 Trussed Rafters Sizing Reference Guide (UK)
Timber grades, section sizes and questions for professional review. No allowable span values are provided; consult official sources and a qualified designer.
Verify against TRADA Eurocode 5 span tables
Numeric span values for trussed rafters in the UK must be confirmed against the latest TRADA published Eurocode 5 (BS EN 1995-1-1) span tables, NHBC Standards Chapter 6.4, and a structural engineer's calculations. Building Control approval is required for new structural work — under Part A of the Building Regulations in England & Wales, Section 1 of the Scottish Technical Handbook in Scotland, or Part D in Northern Ireland. This page is a planning starting point, not a substitute for design sign-off.
About TR26 Trussed Rafter Grade
A grade label alone does not establish suitability. Confirm the actual product, grading evidence and intended use with a qualified designer.
Common species: European Redwood, Whitewood.
About trussed rafters as a structural member
Trussed rafters are factory-made roof trusses that span the full width of the building, eliminating internal load-bearing walls. Designed and manufactured to BS EN 14250 (with legacy reference to BS 5268-3), typically using TR26 grade timber.
Common TR26 trussed rafter sizes used in the UK
Section sizes most commonly stocked and specified for TR26 trussed rafters at UK builders' merchants. Maximum allowable spans for each section must be confirmed against TRADA Eurocode 5 span tables.
| Section size (mm) | Typical spacing (mm) | Max single span (m) |
|---|---|---|
| 35×97 | 400 | verify against TRADA Eurocode 5 table |
| 35×97 | 600 | verify against TRADA Eurocode 5 table |
| 35×120 | 400 | verify against TRADA Eurocode 5 table |
| 35×120 | 600 | verify against TRADA Eurocode 5 table |
| 47×97 | 400 | verify against TRADA Eurocode 5 table |
| 47×97 | 600 | verify against TRADA Eurocode 5 table |
| 47×120 | 400 | verify against TRADA Eurocode 5 table |
| 47×120 | 600 | verify against TRADA Eurocode 5 table |
| 47×147 | 400 | verify against TRADA Eurocode 5 table |
| 47×147 | 600 | verify against TRADA Eurocode 5 table |
- 35×97
- Typical spacing (mm)
- 400
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 35×97
- Typical spacing (mm)
- 600
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 35×120
- Typical spacing (mm)
- 400
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 35×120
- Typical spacing (mm)
- 600
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 47×97
- Typical spacing (mm)
- 400
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 47×97
- Typical spacing (mm)
- 600
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 47×120
- Typical spacing (mm)
- 400
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 47×120
- Typical spacing (mm)
- 600
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 47×147
- Typical spacing (mm)
- 400
- Max single span (m)
- verify against TRADA Eurocode 5 table
- 47×147
- Typical spacing (mm)
- 600
- Max single span (m)
- verify against TRADA Eurocode 5 table
Sizing guidance and UK Building Regulations notes
Project-specific sizing guidance is withheld pending qualified review. Ask a qualified designer to assess loads, supports, connections, exposure and the applicable current standard. No size, spacing or span on this reference page is an approved specification.
How to read a TR26 trussed rafter span table (UK)
- Determine your required span — the clear distance between supports.
- Note your spacing — typically 400 or 600 mm centres.
- Identify your loading category (BS EN 1991-1-1 for floors, BS EN 1991-1-3 for snow, BS EN 1991-1-4 for wind).
- Look up the TRADA Eurocode 5 trussed rafter table for TR26 and read off the smallest section whose span exceeds your required span. Confirm with a structural engineer's calculation.
UK timber standards behind TR26 sizing
TR26 sits outside the BS EN 338 strength-class system — it is a UK trussed-rafter grade originally defined under BS 5268-3 and now produced under BS EN 14250. Design of trussed rafters themselves follows Eurocode 5 (BS EN 1995-1-1) but the timber grading is its own machine-stress-graded specification. Always order from aTRA (Trussed Rafter Association) member fabricator with full calculations and an Origin Certificate.