Let's build a barn! (Moved)

[Dave Shepard]

The Forestry Forum CRASH OF 2007 ARCHIVES
General Forestry => Timber Frame and Log Construction => Topic started by: Dave Shepard on October 15, 2007, 21:35:40

Title: Let's build a barn!
Post by: Dave Shepard on October 15, 2007, 21:35:40
I am going to be building a barn next summer and I would like to get the design process started now. It is for a friend of mine, we don't have an exact design in mind, but it will probably be close to a barn on my property. Jim Rogers, it is the barn you looked at this past summer. My barn is 20'x40'. There are four H bents, and three bays. It has full length plates with step lapped rafters.  I would say the post height is about 16', but the bottoms are rotten away, so no way to verify. Posts and summers are 9"x9", and M&Ts are 2". Braces are 3'x3' layout. We would like to use pine, as it is readily available, easy to work, and less likely to twist or check (than oak). I would like to bounce around some engineering details to try and see how feasible it is going to be to do the frame from pine. Am I going to have to make the posts from a hardwood species, or can I use a larger size to make up for the lower mechanical properties of the pine? I believe the ground floor will be concrete, and the second floor framing is 2x10's joists on top of the summer. Any ideas, inputs, or comments welcome. Thanks.


Dave

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Title: Re: Let's build a barn!
Post by: Raphael on October 16, 2007, 00:43:35
It'd take some pretty beefy pine beams to span 20'.
I checked EWP for replacement part's in Jack Sobon's 18x36 "Classic Timber Framed House"...  :D ...not even close.

Title: Re: Let's build a barn!
Post by: Dave Shepard on October 16, 2007, 00:47:54
Thanks Raphael. Does hemlock get any closer, or are we looking at oak? I don't know what species the barn is. I will try to figure it out, but I am not very good at deducing old timbers.


Dave

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Title: Re: Let's build a barn!
Post by: Bob C. on October 16, 2007, 09:19:13
We just got done with the Pine vs. Oak discussion in the "kingpost" thread. And there are pros and cons of both. You will need to be more specific about the Pine species you have available.  EWP is may not be the best choice but there are some other pine species that might work depending on the design and use of the barn.  If EWP is all you have there are a number of ways to design around it's strength deficiencies.
1) Midspan posts
2) Longer braces
3) Closer bent spacing

Might be best if you give us a little background on the purpose and intended use of the barn, any specific features desired, style and history of surrounding buildings, budget, exterior finish disired, site picture, etc.

Rule of thumb should be limit spans to 16' or less.

Many traditional barn designs used the 3-4-5 rule for dimensioning which results in a very visually pleasing design.

I think the knowledge base and talent is here to come up with a great design.

Come to think of it maybe through collaboration we could put together a little book of plans and sell it to support the FF. Each design named by the person it was designed for.

We can call this the Shepard Barn

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Title: Re: Let's build a barn!
Post by: Dave Shepard on October 16, 2007, 09:30:47
Thanks, Bob C. We have an abundance of EWP, eastern hemlock, and red oak if needed. The barn will be used as a garage downstairs, hence the concrete floor, and I am guessing misc. storage upstairs. This is going to be an evolving design, as my friend doesn't have an exact idea of what he wants. He does like my barn, and is probably going to do something similar. I will try to get some pics up tonight. My barn is in tough shape due to an almost non-existant foundation. It has been leaning at least since my grandfather was a kid. :-\ There is some structural damage due to not being on the foundation, but there doesn't appear to be a problem with the design. One of the post tops is split out, but I think that is because there is a big hole drilled through the top for a steel brace that I don't think was needed.



Dave

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Title: Re: Let's build a barn!
Post by: Jim_Rogers on October 16, 2007, 09:42:49
One of the recent topics on the guild site is about form following function.
To best understand the loads and therefore the beam sizes we need to understand the intended use.
If it's going to be general storage then the second floor load may be as little as 40 or 50 lbs per sqft. But if he's going to be storing automobile engines up there the load could be more...
Center posts and closer bents as mentioned are some solutions.
Thicker second floor decking helps also....

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Title: Re: Let's build a barn!
Post by: Dave Shepard on October 16, 2007, 09:43:39

Still square, just leaning a tad.


Seen better days.


No tie beams on the second floor, except the one just below the windo on each end.


This is the failed post top. I think the combination of the roof load and the big hole, as well as the barn leaning this way are responsible for this failure.


Northeast corner. Note failure in 8x8 plate. There is no post under the next bent, perhaps the cause of the failure? (aside from no foundation? roll_eyes)


Dave

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Title: Re: Let's build a barn!
Post by: Dave Shepard on October 16, 2007, 09:45:59
I will get more info on how the barn is going to be used soon. Is a closer bent spacing going to relieve the load on the 20' summer beams? The decking now is T&G, probably 6/4.


Dave

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Title: Re: Let's build a barn!
Post by: Jim_Rogers on October 16, 2007, 09:51:20
Possibly you're using the wrong term.
A summer beam usually goes from tie beam to tie beam, like gable to gable. The beam that goes from eave wall to eave wall is a tie beam.
This "tie beam" will be 20' and the floor joists could go over this from one bent to another.
With four bents that means the ties are 10' on center apart a much shorter distance to span then using summer beams and having the floor joists run parallel to the tie beams...

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Title: Re: Let's build a barn!
Post by: Bob C. on October 16, 2007, 13:30:28
Dave,

As a garage I would want to make it slightly wider than 20'. (assuming doors will be along long side). I would go to 22or 24' as 20' is a little short to park a full size vehicle and still walk around it comfortably.  What kind of headroom is needed on the second floor at the eave.

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Title: Re: Let's build a barn!
Post by: Dave Shepard on October 16, 2007, 18:08:28
This barn has four H bents. From what I have read, the horizontal part of the H is the summer, both due to its position in the frame, and also that it carries the load of the floor, maybe I am wrong. The floor joists run North-South, parralel to the ridge. The H bents would be about 13 feet on center. I don't know what headroom is needed, but my barn is 7' from floor to top of plate, with nothing in the middle, as you can see from the third photo. I will ask what is going to be stored in the barn, from what I have gathered so far, it is to be used for tractors, not sure about trucks/cars. Going wider may be better, but will certainly require the use of a mid span post. That may be a better idea anyway, as it may allow us to use EWP, which we would like to do. However, it will require rethinking the rafters as well. Thanks for the input.


Dave

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Title: Re: Let's build a barn!
Post by: Jim_Rogers on October 16, 2007, 18:31:10
From the glossary of terms:

SUMMER BEAM. Major timber spanning between other floor
timbers to support common joists. See BRIDGING JOIST.

BRIDGING JOIST. Intermediate floor beam connecting one
crossframe to another and carrying the inner ends of common
joists. See also SUMMER BEAM. Cf. BINDING JOIST.

BINDING JOIST. Transverse floor timber (runs perpendicular to
the ridge) connecting posts and carrying common joists. Cf.
BRIDGING JOIST.


TIE BEAM. An important horizontal transverse frame member
that resists the tendency of the roof to spread the walls. The tie
beam may be found at the top of the walls, where it is able to
receive the thrust of the rafters directly, or it may be found as much
as several feet lower down the walls, where it joins principal posts
in tension connections.

If you don't use the right term here on the forum you'll get everyone confused.....

A tie beam runs from eave wall to eave wall, a summer beam runs between tie beams.....

Jim Rogers

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Title: Re: Let's build a barn!
Post by: Dave Shepard on October 16, 2007, 18:40:30
Tie beam it is! ;)


Dave

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Title: Re: Let's build a barn!
Post by: Raphael on October 17, 2007, 03:06:18
EWP is doable, it just looks really massive when properly sized for heavy loads.
  I was just looking at a huge barn in progress this afternoon, unfortunately the owner wasn't around at the time so I'm not sure what sort of loads he's engineering for.  The entire frame is EWP, post sizes run from 10" up to ~16" square (I also didn't have my tape).  I didn't see a free span of beam over ~12' and the major load bearing beams are at least 10"x14" (possibly16").
  I'll be going back with the camera next week when I'm passing by to or from my new eye doctor's.

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Title: Re: Let's build a barn!
Post by: thecfarm on October 17, 2007, 06:53:09
I don't know nothing about what you are building.But if I had hemlock I would be using that instead of your pine you have.I sell my pine to the sawmills and keep the hemlock for me.The wife's garage is 24 wide by 28 long.The lenght is real good,but it really should be wider for a working garage.This allows 2-9 foot doors and a couple feet in between them and 2 feet on each side of them.Not really enough room to work on something and have some room to move in.We only use it for her car and her tractor.Just depends on what it will be used for.

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Title: Re: Let's build a barn!
Post by: beetle on October 17, 2007, 13:10:53
Aint nothing wrong with EWP, just have the calc's done so you size your posts and beams to your loads. White pine works nicely and is very stable. Hemlock is also easy to work when green and is fairly stable, however, let it season and it is HARD, watch out for that shake.

My 2 cents worth.