28 foot span

[Roy J.]

I don't have an engineered drawing yet, but, I've got a gable roof with a 28 foot span covering an open patio deck. At 5:12 the rafters are going to end up being about 15 feet long. If I could get by using only collar ties on the rafters (because there will be posts set in concrete supporting LVLs) and no other roof bracing does anybody think I could get by using 2x8 material for the rafters?

Just rolling some ideas around. Thank you.

[JWL3RD]

I think 2x8's are borderline for the rafter legnth espeially if you are in an area of the county where a substantial snow load on the roof is possible. I would upsize the rafters to 2x10's to play it safe.

[Don_P]

"If I could get by using only collar ties on the rafters (because there will be posts set in concrete supporting LVLs) and no other roof bracing does anybody think I could get by using 2x8 material for the rafters"

Using only collar ties as opposed to what?, Yes it will be fine if they are at the plate. It will be less fine if the ties are raised at all. This and the minimum rafter dimension are in the codebook under various snow load conditions by different species and grades of lumber.

[Roy J.]

This is in San Antonio, Tx. There are no snow loads and minimal windstorm requirements. The framing material is #2 yellow pine. This guy wants an exposed frame cathedral-looking ceiling with minimal bracing but I don't really see it happening without collar ties and ceiling joists. I mean, it might take ten years but eventually the load is going to push the LVLs out of line. Seems it might be best to wait and see what the engineer comes up with.

[Don_P]

Yup, I'd wait to say anything to the client till he gives his opinion. The main 2 ways are either to tie the roof bottom chord or hang the rafters off a sructural ridge beam, sized to carry them.

[DeeTee]

What about architectural grade scissor trusses? I suppose if they can make them with plates they can make them pretty too. I've also seen this done with timber framing and SIPs. But, you're right, it all comes down to what the engineer/architect says.