Hi
Help with two questions please
1) how do I determine what size rafter ties are required ? Is there a table available?
2) at what point does a rafter become a a “joist”, that is esentially a flat roof?
I can span 14 feet with a 2×4 for rafters but need a 2×10 for a floor joist ?
Replies
Short answer: When you define what the space that the structural member is being used for. This will dictate design loading conditions (dead and live load) necessary to meet presciptive code. If you're not designing outside of prescriptive code, then you're hiring a professional engineer. If that's the case, then let him or her answer your question.
If you are designing within presciptive code, your answer lies somewhere here:
Prescriptive code allowablej oist spans are defined in IRC code under "FLOORS" beginning with table R502.3(1). Find your design loading condition for appropriate table.
Prescriptive code alllowable rafters spans are defined in IRC code under" ROOF-CEILING" beginning with table R802.4(1). Find your design condition for appropriate table.
Ok I found it at the top (802.2)
"Section R802 apply to roofs having a minimum slope of three units vertical in 12 units horizontal (25-percent slope) or greater."
Right there in front of my eyes
Thanks