How Far Can a Roof Truss Span?

Trusses have revolutionised the way we build, from decreasing the cost and increasing the strength for regular homes, to allowing us to construct monumental bridges, stadiums and halls that wouldn't be possible with alternative systems, but how far could a timber roof truss span?

Length

Within reason, you could simply keep increasing timber sizes and adding more webbing to construct a humongous truss—potentially up to 100 metres long—however, there is one big issue... transport. The maximum length a vehicle can be in the UK is 16.5 metres, plus an allowance of 2 metres overhang, meaning a total length of 18.5 metres. Minus a few metres for the vehicle itself and the gubbins between the lorry and the trailer and you're left with 13-14 metres of load capacity.

Height

Although there is technically no legal limit for height, anything exceeding 4.95 metres tall is unlikely to make it under most bridges and will probably need a permit, making it uneconomical (and a bit dangerous) to go over this. Again, minus the height of the vehicle itself and the maximum height of a truss we can transport is 3.9 metres on an artic. 

Conclusion

In some circumstances, we can produce two halves of a truss which can be installed together on site, allowing us to produce trusses greater than 13.6 metres in span, however, this isn't always possible.

So in conclusion, 13.6 metres by 3.9 metres is generally the largest truss deliverable without splitting it in half. Or, in practical terms:

13m span x 30° pitch
12m span x 33° pitch
11m span x 35° pitch
10m span x 37° pitch
9m span x 40° pitch
8m span x 44° pitch

... and so on. If you fancy playing around with what is possible, we've made a helpful calculator that you can find here.