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Tie Beam to summer beam connection/ problem /questions

Started by windfall, July 14, 2016, 02:29:10 AM

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windfall

Building a 24ft x 48 ft barn.  The Tie beams will be 8x12x24ft, supported at 8ft intervals.  The bents will be 12 ft apart.  While following the 5/8, 3/4 rules for mortice and tenon(guidelines), I get worried when I lay out on paper the  amount of tie beam left over after the summer beams from opposing sides come into play.  I was intending on 12x8 summer attached via the shouldered dovetail.  Even using the minimum needed, 1" shoulder and 2 inch dovetail(3 inch total mortice side depth on tie beam) I barely have 2 inches of the  tie beam remaining on top edge between opposing summer beams.  Is this enough?  I am also supposed to support this with a post directly below this connection.  And yes....to top it off I have a queen post upstairs(2nd floor) that would like to be on top of this same spot.  A little crowded here?  Should I use  a wider tie beam?  Can I offset the queen posts upstairs a bit so they do not land on this joint, so as to give a little more meat in this area.  A little help would be greatly appreciated...a lot of help would be even better.  Thanks!

Jim_Rogers

First question is why are you using a summer beam?

Your bent span is only 12' so why can't you just put your joists from tie beam to tie beam?

You should avoid three and four way joints as much as possible. And dovetails as well. There are better joints then the dovetail joint.
If you need to "bind" the tie beams to each other try using a "tying" joist.

Joist pocket:



 

Tying joist end:



 

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

windfall

Jim, I think I got caught up in the design plan and I also wanted to try the various joinery.  The shouldered dovetail for me added a joining
ease as I can just drop them in after the bents are raised.  I like the look of that tying joist! How is the tying joist secured?  A peg from the top side? Does that joinery follow same guidelines for tenon depth, etc..? That joint looks as though it is put in as the bent is raised, any hints on ease of install as I would have joist from 24 to 30 inch on center. While not having a span table for this type of building, does a 6x8 sound about right for this joist?  Floor on top to be 2x material.   

For knowledge sake, now that you brought up no need for summer beams with that span between tie beams, could I just run the joist on top of the tie beams with a slight lap joint on joist and tie beam tops? If so, how is that pegged or held in place?

I will surely stay away from the 3 and 4 joints as much as possible.  This remedy of yours also allows me the queen posts to match up on top and bottom of tie beam with no worries.
Thankyou! And sorry for the multitude of additional questions...learning a lot!

Jim_Rogers

You asked: "How is the tying joist secured?  A peg from the top side?"
and; Yes it is pegged from the top side down.

You asked: "Does that joinery follow same guidelines for tenon depth, etc..?"
and: I think that it is usually a 4" long tenon so that you have enough to peg it off. Sometimes/most times the offset down from the top to the bottom of the tenon is such that the scoop on the bottom matches all the other scoops from the drop in floor joists.
So when you're in the barn and look up they all look the same.

You asked: "That joint looks as though it is put in as the bent is raised,...."
and: Yes, you have to stand up one bent, secure it with temporary brace boards and then insert one end of the tying joist into the standing bent. Support the tying joist mid span or more and when the second bent is raised slide the tenon into the second bent's mortise.

You asked: "does a 6x8 sound about right for this joist?"
and: don't know. You need to figure out the load per joist based on the intended use of the barn floor and then you'll need to know what type of wood you want to use. With this information you can calculate the floor joist size with the beam calculator in the red tool box here on this forum.

You asked: "could I just run the joist on top of the tie beams with a slight lap joint on joist and tie beam tops?"
and: Of course that would work, but not cutting any lap in the top of the tie beam would be best.

Secure with a long timberlok screw down from the top and cover that with the flooring and no one will know you didn't peg it.

Good luck with your project.

Jim Rogers





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

windfall

When using the forum calculator for spans of beams/joist, which number am I actually entering for width and depth of the tenon member?
If the 6x8 is paired down to a smaller size inserted into the tie beam then would I not use the actual resting size of the member?

Thankyou

Brian_Weekley

In general, I think you can just use the full size of the joist in the calculation.  A loaded joist is probably more likely to break in the center of the span than at the ends where it is reduced and sitting on the shoulder of the housing.  Curving the bottom of the joists where they are reduced at the tenon is done to help prevent splitting because you are distributing the stress along more wood fibers (as opposed to a square cut reduction).  Although the tusk tenons are a little more difficult to install during the raising, having the mortises cut near the center of the tie beams is stronger than cutting drop-in joist pockets.  Since a loaded (bending) beam will experience both compression and tension forces at the top and the bottom, taking the meat out of the center of the tie beam preserves more important wood fibers.

This just reminded me of video by MoonHillFarms where he's cutting the haunched housings for tusk tenons in a tie beam:

https://www.youtube.com/watch?v=9lG1Jx_yt3Q

e aho laula

windfall

Thankyou Brian,
I used the calculator last night just to play with different sizes and spans.  I plugged in full dimension but was not sure if it was the correct number to input. That bumps me safely to a 6x8 for the 12 ft span.  Thanks for your help and I am always interested in other ideas/conceps.  Ill try to post a few pics of the work in progress, still milling!
Sam

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