Pole Barn Loft Design

Discussion in 'Off-Topic' started by jpanhalt, Jun 15, 2016.

  1. jpanhalt

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    Jan 18, 2008
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    I do not belong to any building sites, but there are members here with building experience. My pole barn (81' X44') is constructed in the usual way with 6x6 or larger poles on the perimeter with 2X4 girts and T1-11 siding.

    On the inside, the original builder put 4X6 treated posts about every 8 feet apart front to back and 10 feet from the outside walls. He also constructed some lofts supported by those poles. My project is to build another loft on the remaining unused poles. For putting flooring supported by posts, I am used to this type of construction:

    upload_2016-6-15_11-8-47.png

    That is, the beams for the joists rest on top of the posts; joists can be on top of the beams or attached by joist hangers. In my barn, the builder simply nailed the beams to the face of the posts and used joist hangers from the beams. The beams are each a single 2X10 (span = 8 ft). This is looking down at the loft floor:

    upload_2016-6-15_11-15-56.png

    It seems to me that the 2X10 that goes around the loft (maybe called a "rim" board by analogy to a deck) adds nothing to the weight bearing capacity of the loft. If the objective was appearance, that value is lost on me in a utility barn. For one of the three lofts the original builder put up, the posts extend above the floor and are used to secure a safety rail. However, in the other two lofts, the posts are cut flush with the bottom to the flooring. Additionally, the 2X10 sandwich does seem to help remove some of the twist in the support posts.

    Is there any reason not to double the 2X10's and position them on top of the 4X6 posts with steel plates and nails? Is the effect on counter-acting twist sufficient to offset the structural disadvantage on weight bearing? BTW, I plan on a safety rail using posts attached to the beams by lag bolts.

    Regards, John
     
  2. SLK001

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    Nov 29, 2011
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    The vertical posts should be notched to receive the cross beams. In your first picture, the post is properly notched. Using just fasteners to support everything is a "no-no". That needs to be fixed - the fasteners are in heavy shear and could easily fail (pull-out, or even snap off). You can add a 2x6 from the bottom of the beam to the foundation and face nail it to the post (or even better, bolt it to the post.

    You must live in an area where building codes aren't active, because this could have never (or at least "shouldn't have") passed a code inspection.

    If you want to add a loft, definitely use your first drawing as a guide. Just remember to properly pass the loads to the foundation.
     
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  3. wayneh

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    Sep 9, 2010
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    I can't picture what you mean by that. Drawing?

    One reason to choose a construction method is because the local code inspector favors one over another. Have you looked up any relevant local codes?
     
  4. jpanhalt

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    Jan 18, 2008
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    Thank you both for the comments.

    @SLK001
    Interesting comment about notching the posts. Since two, 2x10's will equal the 4x6 narrow dimension, I was planning to just set the beam on top and use a steel T-strap on the outside and a plate on the inside to attach it. The joists will be 2X8 and will possibly be doubled at each post location. Might add diagonal braces as one sees in fancy barns, but I didn't feel that they were entirely needed, except maybe one at each end. Would the notch with much of the load carried on it tend to make the post split? Do you feel the notch is preferred, even when the beam and post are the same width?

    I will be re-doing one of the existing lofts, after mine is completed, and was considering putting 2x6 facings on its posts to carry the load as you suggest.

    The barn is in a rural, unincorporated area. Basically, there are no building codes. There are some state health codes. There is no real foundation in a classic home sense. I suspect holes were bored -- hopefully well below frost line -- then some concrete may have been poured, and the posts were set. There may be some anchoring device on the end of the poles. Some contractors just place the poles in the dirt, like utility poles are done. In another part of the barn, I tried wiggling and pulling one post to get it out with a 3T mini-excavator, but it didn't budge. I removed a couple of utility poles with that excavator, so I know it has enough gusto for doing that, which is why I think there may be an anchoring device on the posts.

    The first picture I posted shows what I meant by nailing two 2X10's together to get a beam and then fixing that beam to the top of the post.

    John
     
  5. Lestraveled

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    May 19, 2014
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    I agree with SLK001 on the beam being attached to the post with nails is a no-no. I am a fan of using matching steel plates, front and back, and bolted together that put the post and beam into compression at the joint. I never use wood screw type lag bolts for any construction. They will loosen in time from moisture and temperature. Any holes you drill into the wood, consider sealing with RTV or other sealant.

    In old log cabin building, the craftsmen angled the joints in an inverted V shape so the joint would not retain water. Look at your pole barn in the same way. Any joint that will hold water will rot.
     
  6. #12

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    Nov 30, 2010
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    Quote from my civil engineering friend, "Everything must be in compression."
    Think about, "jack studs". You can't connect sideways. You must have something in compression, all the way to the ground.
     
  7. wayneh

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    Sep 9, 2010
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    That's an excellent point. I'd also consider slopping on some of this stuff anywhere you cut the wood and especially where it may touch soil. I used it to prepare some deck posts and now that I have it on hand, I apply it liberally to any wood going outside. It repels fungi and even insects. Kinda smelly, so wear disposable gloves.

    http://www.walmart.com/ip/Zinsser-1...82693831&wl4=&wl5=pla&wl6=90202089191&veh=sem
     
  8. jpanhalt

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    Jan 18, 2008
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    Compression, unless it is fibrous. ;)

    The crux of my question is not how I would do it starting with a clean slate. But whether there are good reasons to have done it the way it was done. It is not even built like a typical deck with a rim board. There was certainly no savings of wood.

    On the other hand, the original builder was a general contractor, and it was a home he built for himself and lived in until his 3rd divorce. All three lofts that he built are built the same way. It is tempting to say he built the first wrong and had a bad habit, but I am not so quick to dismiss that construction style. The only thing I could think of was counteracting the twist of the treated 4x6 posts as they dried, but that seems pretty weak.

    John

    EDIT: This structure is a loft in a barn. It is not exposed to outside weather or earth.
     
  9. shortbus

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    Sep 30, 2009
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    When younger I helped put up some pole barns. The header beams were always two 2x10's one on each side of the posts and a short diagonal in between the header to the posts. Just nailed with a 5 nail pattern. This was the way the plans that came with the barn kits from 84 lumber called them out. couldn't find a picture that was exact but this is close, didn't use the bolts that they do. From this site - http://www.brubakerllc.com/why-use-us/what-makes-us-different bull-strong.jpg
     
  10. jpanhalt

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    That is a significantly different arrangement. In the case you show, the 2x10's are supporting joists (or joist-like beams) on either side. In the case I described, the outer 2x10 (rim board) supports nothing.

    JOhn
     
  11. #12

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    I like the shortbus picture because everything is in compression except the steel, which is in sheer. The double beam eliminates the load being off center to the pole and thus nullifies bending (torque) on the pole. If you can't go on both sides of the pole and you don't want to run a jack stud clear to the ground, at least use steel for the sheer points, and I don't mean nails.
     
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  12. SLK001

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    Nov 29, 2011
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    That arrangement becomes an inverted pendulum and is unstable. With a lot of external steel, you can make it "less unstable". Notching of a beefy post will not make it more inclined to split, provided that you securely attach the beams to the post (use galvanized through bolts). With the beam secured to the post, they will act as a single entity and properly channel ALL external forces to the foundation.
     
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