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Community and Q&A

Green Pine Joist Spans

Daniel Howe | Posted in General Questions on

Hello GBA Brain Trust …

I’m in Rhode Island, planning to build a 1 1/2 story garage-workshop using locally milled full-dimension green pine. For the most part I think I have a handle on how I’m going to do it (platform frame, 2×6 studs @ 16″ o.c.) — although I welcome suggestions. The upstairs loft will eventually be insulated and finished for use as an office. My reasons are aesthetics and cost: local green pine is running well under 1/2 the price of KD of the same nominal dimensions at the big boxes.

A big hole in my research: I cannot get information on floor joist spans. The garage will be built on a slab, but I want a clear 16′ span. KD 2x12s at 16″ o.c. would handle this pretty well, I-joists or trusses would be fine, but what about green? I’m worried about deflection, obviously. The load “upstairs” will not be extreme (household storage, office furniture, books away from the center) but it would be terrible to build this thing then have it sag. A center beam or posts are not desirable as this span is intended to be as open as possible.

Anyone have info on spans for green pine 2×12?

Related: I was thinking of using green pine beams as headers in a few places.

Thanks all.

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Replies

  1. Expert Member
    Michael Maines | | #1

    By, "green pine" do you mean freshly sawn eastern white pine? There are many different species of pine but eastern white is the most common in the northeast, followed by red pine. Each species has different structural characteristics. Grade matters as well; is the grain straight (within 10° of the long dimension); are there knots, and if so, are they tight or loose, large or small, and in the center or at the edge of the board?

    White pine is not as strong or stiff (slightly different engineering qualities) as other conifers used regularly in construction. I'm not sure if RI allows visual grading of lumber; here in Maine it is allowed but many states require machine stress rating to gauge strength. If it's allowed, you won't find span tables, but an engineer can do the required calculations for you. This publication explains grading rules: https://www.nelma.org/wp-content/uploads/2013/08/Section_5.pdf.

    Generally speaking, white pine is about 75% as stiff as other framing lumber used in the northeast, and allowable spans relate directly to stiffness, so as a starting point you can assume that a white pine 2x10 will span about 75% as far as a spruce 2x10. But you should get an engineer to fine-tune the calculations.

    1. Daniel Howe | | #10

      Yes, fresh sawn eastern white pine. I don't have a handle on whether the mill I'm looking at in East Freetown, MA does grading, but I'll find that out. Based on that 75% rule it sounds like I might be out of luck: SPF 2x12s reliably span 16' but white pine is unlikely to.

  2. Expert Member
    Malcolm Taylor | | #2

    User...832,

    Unfortunately using green or ungraded lumber can open a can of worms, as most codes don't accept it as framing material. Your first stop should be your building inspector to see where you stand.

    1. Daniel Howe | | #11

      Checking.

  3. plumb_bob | | #3

    The shrinkage (and potential twisting) that your frame will experience due to green lumber drying may have serious consequences- plumbing stacks and drywall come to mind. Also, lumber above +/- 19% moisture can grow mould in the right conditions.
    Who will grade this lumber? Will it be planed to size?
    Food for thought- bottom plate, 2 top plates, joists and rim boards, possibly more plates for a 1/2 story pony wall. If all of the pieces above shrink by 1/8" -1/4"the total shrinkage could substantial.
    An acceptable place for green boards is use as board and batten siding- you can go back and tighten everything up after the shrinkage has occured.

  4. Expert Member
    Zephyr7 | | #4

    There aren't any span tables for green/ungraded lumber because it's essentially "mystery wood". The span tables allow for species (spruce/pine/fir (SPF), and a bit different for southern yellow pine (SYP)), and for the visual grading like "1", "2", etc. MSR and the like are actually tested by a machine and graded for yield strength. With any of those, the properties of the material are predictable enough that there are published tables stating allowable span lengths for given loads in pounds per square foot.

    For green lumber, what are you starting with? What species? Are there knots? How many if there are? Are the knots loose or tight? Without knowing any of that, there is no way to even guess at what it might be able to do holding up a building. Codes generally don't allow the use of ungraded material for exactly this reason.

    Your local mill might be able to help you here if they have a place that will grade some of their lumber for you. If that doesn't work out, you can always use the green lumber for trim or landscape work where the structural unknowns aren't an issue. Remember though that green lumber will twist, warp, and crack when it dries, so don't expect it to stay straight and flat the way kild dried lumber does (or at least is supposed to :-).

    Bill

  5. Walter Ahlgrim | | #5

    If you have not worked with green wood before you need to understand that over the next 2 years the woods width and thickness will be reduced by 7-15% while the length remains more or less unchanged. Boards from close to the center of the tree will want to twist more than ones farther away.

    Note as the wood shrinks a gap will grow behind any drywall so it is loose so when someone presses on the wall board the screw heads poke thru the surface. You may want to wait 2 years before installing the drywall.

    Before there were lumber grades and span charts they just built what looked right. The ones that were oversized survived the lesson is go big.

    Walta

    1. Daniel Howe | | #12

      I was thinking the same thing about drywall (or another interior finish). Thoughts on platform framing with green-framed walls and a KD platform? Or is that just asking for (more) trouble?

  6. Tyler Keniston | | #6

    See this calculator: https://awc.org/codes-standards/calculators-software?utm_source=google&utm_medium=search&utm_campaign=2020

    (American Wood Council Span calculator)

    Note that is does ask for grade, which is sort of the hitch described by others. For someone who knows wood, visual grading really isn't a black box, though for code you may need more than just your own eye. If you view wood as a homogenous product instead of a slice of a tree, it may be difficult to do any on-the-fly grading.

    Using green lumber certainly requires an understanding of wood, but it's not impossible. I think some of it's 'drawbacks' get overstated because it takes another level of interaction with the material. It's probably not for the masses. Certainly not for production builders.

    Robert Riversong who used to frequent GBA praises it (I think he used mostly Eastern Hemlock). https://riversonghousewright.wordpress.com/about/14-building-really-green/

    I think you may find that 16' clear span with eastern white pine (if that's what you mean by pine) is a stretch, unless you're talking very large timbers or are willing to fudge on your deflection limits.

    One other note about the twisting problem: green wood is actually quite straight seeing as it's straight off the saw-- usually straighter than KD lumber. The key is getting it nailed down in place so that it has restraint as it dries. It's true that if you put a pile of green wood in the elements (mainly sun) you should expect some potentially significant warping. Eastern Hemlock is some of the worst for this. White pine isn't as bad but, as stated, isn't as strong (generally used for finishes, but also used by some timber framers). You may want to look to timber framers for a source of more info on using green lumber.

    1. Daniel Howe | | #13

      Useful calculator, thank you! I'm checking with the mill about grading. FWIW the calculator gave exactly the same numbers for eastern hemlock (either balsam or tamarack) as for eastern white pine: 2x12, either select structural or No. 1.

      Riversong's blog influenced my interest in building with local green lumber. I reached out to him with different questions at his email awhile back but I'm guessing he's retired, passed away, or maybe in a lotus position on a VT mountaintop.

      One thing I'm missing in these discussions: will the *greenness* influence flexion/deflection? If so one option I kicked around is to build the floor and support the middle for six months or so till it "dries in."

  7. Daniel F. Vellone | | #7

    Will all due respect to the expertise offered on this site, your question might better be directed at the Timber Framers Guild site, or the Forestry Forum. Using rough-sawn green lumber is likely going to buck up against code compliance, and so won't get addressed in the manner you're after here.
    Far as grading goes, most sawmills worth their name will offer a #2 or better letter of grade on request that the codes officer should accept, but as you might already know, doesn't have to. Hard to believe the lumber at Home Depot and Lowes earn this grade.
    Even at my location which abounds with local sawmills, it took quite a bit of back and forth to get codes to relent to roughsawn.

    1. Expert Member
      Deleted | | #8

      Deleted

    2. Daniel Howe | | #14

      Wait, I thought this was GREEN BUILDING advisor? (j/k). I will check those forums.

      More seriously, my notion of green construction is at least as influenced by the 1970s Mother Earth News magazines my parents had in the house as by the latest product from Siga ... I'm a fan of repairability, localism, and a generally conservative approach.

  8. Joe Norm | | #9

    He did write "full dimension" which offers a lot more meat than a nominal 2x12

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