Ideal wood to use for long spans?

Dork · Post by **Dork** » Thu Mar 18, 2004 12:01 pm

Ok.. I'm running through structure possibilities and am thinking about using wood instead of the usual PVC and metal conduit. What would be the preferable wood to use for an 8-10 foot span that needs to support a couple of people standing on it? Cost, weight, and burnability are my mail concerns.

I got inspired by this picture

robotland · Post by **robotland** » Thu Mar 18, 2004 12:26 pm

I'd suggest good 'ol pine 2x4's or 6's, doubled or tripled for loadbearing depending on design and fastened with bolts. Plates or joiners of 3/4" plywood (except for the burnability, it rocks) or steel, to be fished out of the ruins later. A span like an ARCH, or a BRIDGE?
I remember admiring that tetra-structure, too.......4x4 posts and steel with 1" bolts or thereabouts.....
I don't know how it works in to the construction plan, but I noticed that the plain pine decking that I used for my dome deck dried, cracked and split QUICKLY out there.....pays to be picky at the lumberyard.

juanicoheal · Post by **juanicoheal** » Thu Mar 18, 2004 12:33 pm

sounds heavy and expensive, but hey, inspired!

Are ya gonna burn it?

Dork · Post by **Dork** » Thu Mar 18, 2004 12:36 pm

When I say span, I mean a long horizontal piece supported at each end. It would be a shade area underneath with at least one level of seating up above.

Did all of the decking boards crack or just ones with knots?

robotland · Post by **robotland** » Thu Mar 18, 2004 12:58 pm

....I think just the ones with existing flaws. All of my deck wood went from outside-in-Michigan 80% humidity to on-the-Playa-dry-as-a-bone, and the shock was too much for it.....There were no catastrophic failures, as the decking was all well supported, but on a loadbearing span it'd be a different story......Do you aspire to a completely span-supported structure, or will you have verticals?

Dork · Post by **Dork** » Thu Mar 18, 2004 1:27 pm

I was hoping to only have verticals in the three corners. I'm definitely not set on it being made of wood.. just examining the possibility. I like working with metal but with wood it would be so much easier to just nail on a bench and if I decide I don't want to haul it home, just burn the thing.

Is steel that much lighter for supporting an equivalent load? My only real experience with wood structures has been doing what someone else has told me.

LeChatNoir · Post by **LeChatNoir** » Thu Mar 18, 2004 2:09 pm

I think you’ll find that steel is gonna be heavier to deal with all the way around. Here’s a suggestion for you:

I needed some scaffold boards for doing rock work. I took a 14' - 2X12 and nailed two 14" - 2X4's vertically underneath (nail through the 2X12 into the 2X4 with 16d’s). Then three 11-1/2" - 2X4's (length cut to the width of the 2X12) perpendicular under that... one at each end and one in the middle. Two of these dudes set up slightly apart with plywood layed over that and nailed down. Two of us, a bunch of rocks and mortar buckets had no problem at all. I made mine out of pressure treated (yuk...) And have had them for years. Portable by one, easily ported by two. And please don’t burn PT wood... please. These are worth building to keep if you can bring them back with you. Many uses, especially if you live in the country, like myself. But then again I fret over wasting any little thing.

If you need more clarification, let me know...

precipitate · Post by **precipitate** » Thu Mar 18, 2004 3:10 pm

> Did all of the decking boards crack or just ones with knots?

We had a wooden structure (24x32 partially-roofed building) for three
years out there. We were able to reuse a lot of our wood, but not only
flawed pieces warped during the drying process. Some completely good
pieces became twisted, bent, or cracked. It pays to be picky, and it pays
to have a couple extras. We used mostly 8' 2x4, with some 2x12 for
horizontal crossbeams, and plywood.

III · Post by **III** » Thu Mar 18, 2004 3:25 pm

you may want to consider using engineered lumber. it's much more resistant to warpage, and you can get ibeamy looking things that concentrate the material in areals of maximum strain for that sort of load.

if you plan on using regular wood, i would suggest at least 2x8's at 16" centers for the spans, and that doubled for the ends.

robotland · Post by **robotland** » Fri Mar 19, 2004 6:33 am

.....Bob?

Ducky · Post by **Ducky** » Fri Mar 19, 2004 11:37 pm

If Im correct you are building a three post structure? I use metal framing brackets...for a four post structure....so that wont help. As far as wood went, ive used both pine and pressure treated, the latter being much heavier. Both have worked great. Pine does rend to warp, but if your burning it anyways.....Wood has worked like a charm so far...so long as its secured IN and TO the ground! Before you attach any masts (tarps). They may make metal brackets you can use, and I recommend them, if possible.

Ideal wood to use for long spans?

Ideal wood to use for long spans?

Wood Structure