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Re-using Barn Timbers

Started by ballen, October 22, 2010, 07:35:37 AM

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ballen

Ironwood,
Oh no, don't even say that out loud!  So far, no mention by anyone on my team about .... Steel. It's even hard to type!

Jim_Rogers

Quote from: ballen on January 14, 2011, 10:11:35 PM
Jim, Do I use the same calculator and just add up all the weights?

To continue you need to figure the area that one tie beam will support first.

Based on what you have said, it is one bay, and one aisle.
The bay distance is 12' and the aisle distance is 14'. But only half the load goes to a tie in bent one and the other half goes to the tie in bent two. So that means 6' by 14' or 84 sq ft. Times the load of 40 lbs per sq ft = 3360 lbs on the tie.

Use that amount, change the span to 168, enter a timber size, and yes, if you're using the same type of wood then enter the same values.
Adjust the depth of beam until you find one that passes. Usually the width stays the same width as the posts.

Let me know how you make out.

Jim
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Dave Shepard

To step back a little to the plinth issue. I am working on two Dutch barn restorations, and both of them have head height issues. In the first barn, the four interior purlin posts will be put up on marble plinths to achieve head room. On the second barn, the entire barn had all of the posts cut off so a stanchion barn could be installed underneath. Many posts will be new, and any that are being saved will have new, slightly longer, bottoms scarfed on. As far as reusing old structures, the best way is to have an architect familiar with timber frames do your design work, as he/she can stamp the plans. An engineer is most likely going to go straight to a steel exoskeleton. In the case of both of these Dutch barns, the rafters, which are in excellent condition, will not meet code as a barn. We will have to have additional structural support above the roof sheathing. Fortunately it will be hidden.
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

ballen

Jim,

Based on what I have gathered so far, I will need 8x10 ties (qty 4) and 6x8 joists (qty 8, spaced 48" OC) for my first bay.

In Sobons "Historic American Timber Joinery", he discribes the joint like the one shown below as a "Strengthened Tenon" and says: "The ultimate tenoned joist has a sloped shoulder above the tenon that brings into bearing the entire depth of the joist while keeping intact the vital compression wood of the carrying beam." However, his example joist is a lot smaller relative to his example beam. 





Do you think this will work as shown for me? Would you reccomend a different joist connection?

Bill

ballen

Dave,
On the barn you raised the purlin posts....won't that require all new (longer) rafters?  I have same issue with head height under my purlin ties.

With regard to an architect vs an engineer, my local inspector requires an engineers stamp, not an architects.  Luckily, I have found an engineer who is active in the Timber Framers Guild and is sympathetic to my cause!  Hopefully, no metal will be required.

Dave Shepard

All of the posts in this barn have been cut off, so they will all get raised. Here in MA, if the architect is doing all of the work, they can stamp the drawings. They cannot just stamp the engineering details.
Wood-Mizer LT40HDD51-WR Wireless, Kubota L48, Honda Rincon 650, TJ208 G-S, and a 60"LogRite!

DrewS

Ballen,
Check out Benedict Antique Lumber and Stone in Susquehanna County.  Owners name is Jesse Benedict.  He would be able to help you and he's local.
DrewS

Jim_Rogers

ballen:

It would be best if the mortise in the tie beam was in the middle vertically. That is known as the neutral axis as the fibers are not in compression or tension.
Then scoop the bottom of your joist to the bottom of the tenon.....

Does that make sense to you....?
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

ballen

Jim,
You mean something like this?


Jim_Rogers

Yes, if that mortise is in the middle of the tie beam.

It will be a challenge to assemble as you'll have to hold up all the joists while you raise the second bent and insert each end into the tie beams. But it can be done, and when you're ready I can describe how to do it.
Also, I would plan on spanning either side of the center post, do not put a joist into the center post.

Jim
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

ballen

So, here's the floor system for my first bay.  The 6x8" joists are 48" on center and straddle the center beams.  Is it OK they are in the end beams?  Should I use the same joint there?





Thanks,
Bill

Jim_Rogers

Normally all bents, meaning interior bents, are framed towards one gable end, so that it's easier to make everything line up and go together.

Your brace locations show me that you have the gable bent framed to the outside and the second bent framed to the inside. That is ok, I've seen things done this way as well.

This would move the tenon of the tie away from the tenon of the joist, which at the wall is usually called a girt or a connecting girt.

This joist/girt will not be holding up as much floor as the other joists so it doesn't need a completely "the same" joist pocket in the post. And it doesn't need to be as wide, which would reduce the size of the tenon to the post. You may want to size this joist/girt smaller, as it will also have the support of the enclosure system fastened to it on the outside.

You'll have to do a test of the two joints in the post and see how much post is left.....

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

ballen

Thanks Jim,
I will run the calculations for 1/2 the load on the end joists (girts) and see where I end up.
I am working with a pre-1850 barn frame which was referenced as you noticed...outside bents to the gables, 2 inside bents to the middle bay. It has some other unique properties like 1/2 dove tail on the main ties, and plates that overhang the exterior with a slot to accept the top of the siding...pretty cool.

ballen

OK,
I ran the calculations and can go with a 5x7 "girt" at the 2 ends of the first bay. See the attached drawing.  The first bent posts are 9x10, the second bent posts are 8x10.  The main tie is 8x12 and the floor system ties are 8x10.  So...at the worst "clash point", I'll have an 8x10 and a 5x7 hitting at the same point (90 degrees apart) on a 8x10 post.  Will that be too much wood cut out of the 8x10 post?





Thanks,
Bill

Jim_Rogers

Due to the fact that I haven't taken the time to carefully model your joints, and I can't say for certain if it is or isn't too much removed. Your engineer will tell you when he reviews your frame design.

As the floor joist is holding up less load, I sometimes make it a "slide in" floor joist. That is after the frame is raised, I slide it in from the outside. And don't make a fancy tenon end on it just a bearing end.

Something like this:

.

Then the enclosure system will hold it in place or you can attach a metal strap across the outside where it will be hidden, but will hold the joist in place.

Jim

Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

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