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offsetting joists #13490 12/10/07 09:20 PM
Joined: Aug 2006 Posts: 242 Kingston ,NY T timber brained OP Member
OP timber brained Member T Joined: Aug 2006 Posts: 242 Kingston ,NY	I was wondering if it is a good idea to offset the joists' joint location into a tie beam that also has joists joining into it from its other side as well. It seems it may weaken the tie beam more if the joists both join the beam in the same location. It would not be that difficult to layout the joist mortises on one side of the tie beam offset from the opposing joists pockets. tb

Re: offsetting joists [Re: timber brained] #13491 12/10/07 09:58 PM
Joined: Apr 2002 Posts: 895 Minneapolis, Minnesota daiku Member
daiku Member Joined: Apr 2002 Posts: 895 Minneapolis, Minnesota	Yes, if they were alternated evenly, that would weaken the tie beam less. How will it look, though? CB. -- Clark Bremer Minneapolis Proud Member of the TFG

Re: offsetting joists [Re: daiku] #13499 12/11/07 10:03 AM
Joined: Dec 2007 Posts: 1,882 Maine T TIMBEAL Member
TIMBEAL Member T Joined: Dec 2007 Posts: 1,882 Maine	It's my understanding that reguardless of where the pockets are placed, you have compromised the strength of the timber. So alternating the pocket layout shouldn't help in the strength department. If the timber is sized correctly one could place any number of pockets in any location. How about placing the members on top of the tie/girt and using no pockets. Tim

Re: offsetting joists [Re: TIMBEAL] #13501 12/11/07 03:55 PM
Joined: Nov 2006 Posts: 850 Charleston, SC mo Member
mo Member Joined: Nov 2006 Posts: 850 Charleston, SC	I agree with just sizing the carrying beam accordingly. However if you did offset joists you could create maybe some aesthetic interest. Maybe with the help of some partitions and the right spacing between On Centers of each bay you might be able to make the whole "room" offset from the previous when in fact it is not.

Re: offsetting joists [Re: mo] #13514 12/12/07 09:31 PM
Joined: Jan 2007 Posts: 603 Joliet, IL. brad_bb Member
brad_bb Member Joined: Jan 2007 Posts: 603 Joliet, IL.	You may get some slightly stronger areas locally, but you cannot calculate it or rely on it for sizing your tie beam (not significant). I wouldn't. You should assume that the area where it's notched is doing nothing in bending(bending stress). I speak only from a mechanical engineering standpoint and not necessarily from timberframing experience. http://www.bradstimberframeprogress.blogspot.com

Re: offsetting joists [Re: brad_bb] #13517 12/12/07 10:08 PM
Joined: Nov 2006 Posts: 850 Charleston, SC mo Member
mo Member Joined: Nov 2006 Posts: 850 Charleston, SC	This might be a question for the engineering section. I'll try a specific example for clarity. 8x10 Tie. Span=X if it too long we will just put another post in the middle. 1" Housings. 4x6 Joists on both sides of Tie. After the tie housings are cut you still have roughly 4" below the joist on the tie that has not been removed. This wood is in tension. On the top of the tie you would have compression wood. Since the joists would fill these housings in the compression wood (4.99" anyway) wouldn't you have only a 1.01x1x4" section that is sacrificing the strength of the tie. If you housed joists only in the compression wood of the tie-beam would it only take away a very minimum of its original stability (no housings at all). Any elaboration on this example would be appreciated. Mo

Re: offsetting joists [Re: mo] #13519 12/13/07 02:11 AM
Joined: Aug 2006 Posts: 242 Kingston ,NY T timber brained OP Member
OP timber brained Member T Joined: Aug 2006 Posts: 242 Kingston ,NY	thanks all. Daiku , you are right to ask how it would look? I am not sure as I have never seen this. I thought maybe you might have though. Its probably not woth finding out going by these responses though. perhaps better that I use the extra energy to frame the joists using soffit tenons, as they seem to be the superior joint in this location. Thanks again everyone for the critique. Always helpful. tb

Re: offsetting joists [Re: timber brained] #13522 12/13/07 11:26 AM
Joined: Dec 2007 Posts: 1,882 Maine T TIMBEAL Member
TIMBEAL Member T Joined: Dec 2007 Posts: 1,882 Maine	Yes, soffit tenons are very nice. They handle the structual issue and are easy to cut however, they bring up an assembly problem, if you are willing to deal with that they are a great way to go. I put in a couple soffit tennons, to hold things stright etc., with the rest, drop in pockets. As for a one inch deep housing that seems a bit on the short side, although I know a lot of folks use that set up. Maybe I am being a bit to traditional using two inch plus deep pockets. If its a barn/out building I still have no problem simply putting the joist on top of the ties, some times no lay out just knock around until they look well spaced, the joist are usually sawn only on two sides, with tha bark pealed. Tim AA

Re: offsetting joists [Re: mo] #13535 12/14/07 01:54 PM
Joined: Apr 2002 Posts: 895 Minneapolis, Minnesota daiku Member
daiku Member Joined: Apr 2002 Posts: 895 Minneapolis, Minnesota	Originally Posted By: mo This might be a question for the engineering section. I'll try a specific example for clarity. 8x10 Tie. Span=X if it too long we will just put another post in the middle. 1" Housings. 4x6 Joists on both sides of Tie. After the tie housings are cut you still have roughly 4" below the joist on the tie that has not been removed. This wood is in tension. On the top of the tie you would have compression wood. Since the joists would fill these housings in the compression wood (4.99" anyway) wouldn't you have only a 1.01x1x4" section that is sacrificing the strength of the tie. If you housed joists only in the compression wood of the tie-beam would it only take away a very minimum of its original stability (no housings at all). Any elaboration on this example would be appreciated. Mo Mo: I don't think this analysis is valid. You can't count on the joist filling that housing. For one thing, the joist may shrink in width, and not fill the pocket. The joist may even be cut slightly undersized. And the wood fibers in the joist are running in the opposite direction, so you would be compressing the side grain. You have to reduce the section in the tie beam by the full size of the pocket before doing your load calcs. -- Clark Bremer Minneapolis Proud Member of the TFG

Re: offsetting joists [Re: daiku] #13541 12/14/07 05:34 PM
Joined: Mar 2002 Posts: 1,687 Sneads Ferry, NC, USA J Jim Rogers Member
Jim Rogers Member J Joined: Mar 2002 Posts: 1,687 Sneads Ferry, NC, USA	I took an engineering course at Heartwood school where we discussed this subject. They gave us some guide lines to go by. I created a drawing based on these guide lines. Here is a drawing of drop in floor joist to tie beam connection "rules of thumb." See if this is helpful to you: The dimensions are just for this example. If you change the tie beam to a deeper beam you can adjust the floor joist size and the depth of the pocket. The purpose of the scoop at the bottom of the floor joist is to "eliminate the point of fracture," which would be created if you just cut out a 90° notch. This type of scoop or curved cut can be seen in many old structures. Any comments are welcome. Jim Rogers Whatever you do, have fun doing it!

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