Hi all,
I’m soon to be building a screened porch in Landisburg, PA. My question is about rafter spans. I’ve used the American Wood Council’s online span calculator, which tells me that for my application (a 1 in 4 pitch shed roof over a room that’s 15′ 5″ across, with no live load above) I should be able to use 2 x 10 Southern pine at 24″ on center. That’s fine with me. In fact, my instinct would be to go with 2 x 10s at 16″ on center, just in case there’s a whopper of a snowstorm down the line.
Is it realistic to think that I’ll be able to get decent 2 x 10s at 16 feet–or more–from a reputable lumberyard, or should I be thinking about using an i-joist product?
Any thoughts would be greatly appreciated…
–Olsh
Replies
2x10s are usually pretty good since you need a fairly large tree to make 2x10s. Of course look them over as you use them.
I can get them up to 22' easily in good shape.
but I'd go 16" OC. The book may say it can handle the load at 24" but there are other considerations, like sags in the roof and sheetrock
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Thanks, Piffin. By the way, I enjoyed your posting on your trip to Ireland. The pics and the travelogue certainly stirred some envy among Breaktimers. And congratulations on managing to balance the taking of the pics with your wife's quest for napery. I liked that part of the story a lot. -Olsh
no intent to stir envy, only to sharte what was a fine time. I've had darn few vacations in my life. This one was worth two or three.
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I find the local 2x6 and 2x10 to be much better lumber than the 2x8 or 2x12.
But since the lumber is graded there is little need to worry.
Seems to me the longer and wider lumber gets, the better it looks. At the high end, the 2x12 I see is almost uniformly straight and without wane. But any lift of 2x4x8' contains a large number of propellors and hockey sticks. 90% will have wane of some sort. Both graded #2 & Better, but visually miles apart.
Having said that, this is all structural material, not appearance grade. Some wane won't hurt for studs. Like any good carpenter, the mill cuts the big stuff first; 2x4's come from what's left and the 'pecker pole' trees.