Roof truss spans...

21 Dec 2009
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United Kingdom
What I need to know is. What section size timbers would I need to span 30' (wall to wall). There will be a wall in the centre to support ceiling/floor timbers. It's for a barn and the 'roof space' will be used to store square hay bales! The roof covering will be of steel profile. It is fairly expose and will be build in the very north of Scotland. There is no building regulation involved.

Any ideas would be appreciated.

Thank-you in advance...

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This Q of span tables has been done to death on this site - research it and /or google the same. Be clear as to what you are talking about - roofs trusses or chamber joists?
If you are making a truss, then the timber sections can be smaller than those for a traditional cut roof, as the truss acts in a kind of load sharing arrangement. In which case you need some specialist design calculations for the truss as a whole

Otherwise, then is no way you are going to get the bottom tie to span 10m, or even 5m with your intermediate support
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Truss member sizes are based on clear span, pitch, overhang at eaves, load and configuration.. Unless you intend to make them yourself its alot simpler to contact a truss manufacturer for more advice..
We are considering laminating the trusses to acheive the span as well as laminating the rafters to include 2 queen posts.
Slots etc for joints will be acheived using polystyrene to create a mortice and tenon method of construction when sections are assembled.
timber laminate cross section will be 5 sections of 18mm x150mm. The joints will be bolted through the glued joints.
Placed at 600mm centres we feel this will acheive our goal...

Unless you know other wise!

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