Hey all,
1st post on here hope you all are doing well.
I’m having trouble finding engineering specs on rough sawn lumber. I’m trying to get a three foot cantilever for a spiral staircase off a second story deck.
I am trying to go with 2×8’s because of space restrictions at the ledger. I’m hoping to get a bit more cantilever by using rough sawn and we like the look too. If I can get it with dimensional lumber OK but my interpretation of the code doesn’t allow it. I’m open to other ideas to maintain 2×8 joists.
We are 12′ from Ledger to a steel H beam support. Were trying to get an additional 3 in front of the beam. Were planned for 16″ on center but i’m open to ideas if 12″ oc gets us to the three foot we want to enter the spiral staircase.
Thanks in advance
Replies
What makes you think standard lumber is inadequate? Assuming you can get graded rough lumber, all you'll gain is at most 1/2 inch in joist depth. (The width doesn't make much difference.) If your current calculations are for #2 and better, consider select struc.
Actually, 3x8 df will work @ 16".
I am not sure what you are meaning by "engineering specs" for rough sawn lumber. The section properties are not hugely different from standard dressed sawn lumber, but can be calculated pretty easily or are tabulated in the attached document. The bigger issue is that I am not aware of any agencies that grade rough sawn lumber (difficult to visually grade rough cut..) I would think any benefit you get from the slightly larger section would be outweighed by the assumed low grade.