Hi,

I'm looking to build a double garage 5.6m wide by 5.3m deep. I am reusing some timber roof trusses; so I will need to span a purlin with a width of 5.6m on which to rest the 4.2m long roof trusses.The trusses are 38 degrees in pitch and from the internal span beam, the truss will then further extend downwards in the same pitch by 1.2m - giving a front roof section of 2.1m to the ridge and then 3.2m to the rear with the supporting purlin at 2.1 / 1.2m

The timber trusses are of 40mm softwood construction of a modified queen scissor type design - The roof will be covered in 12mm sterling board and have clay pantiles as the roofing material.

My question is; I'm thinking of using timber rather than a steel for the purlin -What size and grade of timber(s) should I use for the load bearing 5.6m span?

Thanks in advance for any help on this.