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What kind of joint is this/am I an idiot? #34694 08/08/19 03:08 PM
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MaxHardcastle Offline OP
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I am building a small office for my wife to do work from home and I am considering ways of omitting the need for joist hangers. I donít think this is specific to TF but if there is anyone who knows the answer to this it is probably a timber framer. The best thing I can think of is to cut my joist ends trapezoidally with the short side down, and notch the beam they are attaching to. End beam is 4x8 Doug fir and joist is KD 2x8. Would use lag bolts to prevent spreading force. Also open to other ideas!

https://postimg.cc/p9hTsLgF

Best, Max

Re: What kind of joint is this/am I an idiot? [Re: MaxHardcastle] #34695 08/08/19 08:39 PM
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D Wagstaff Offline
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I call it, Diminishing Stub Tenon. Well, it has it's place and in that place it's a good joint I have found.

Re: What kind of joint is this/am I an idiot? [Re: MaxHardcastle] #34696 08/09/19 09:56 PM
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Roger Nair Offline
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I would call that joint a let-in sometimes used to place minor pieces in an existing larger framework. For instance, I have found posts that were notched in that fashion to secure wall purlins as a nail base for vertical siding. I would not approve of that joint as illustrated for supporting floor joist. Look for other technique such as ledgers, tusk tenon, soffit tenon, direct bearing, half height etc. I have two objection to the illustrated joint: no level bearing and the beam is weakened by substantial cutting of the upper portion of the beam.

Re: What kind of joint is this/am I an idiot? [Re: MaxHardcastle] #34697 08/10/19 04:09 AM
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MaxHardcastle Offline OP
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Thank you both for the replies and for the suggestions. Looks like I have more reading to do - I have never heard of those alternatives you had suggested.

Re: What kind of joint is this/am I an idiot? [Re: MaxHardcastle] #34698 08/10/19 05:08 PM
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Cecile en Don Wa Offline
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Yes, it's for incidental work added in to an existing frame certainly not intended for primary construction by any means.

Re: What kind of joint is this/am I an idiot? [Re: MaxHardcastle] #34699 08/11/19 02:00 PM
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Jay White Cloud Offline
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Hello Max,

In, and of itself, there is nothing wrong with your joint selection as presented...

It is much less common (it seems?) in European timber framing modalities compared to Asian systems (going by several names of which I would have to look up as I can't recall them from immediate memory,) and other woodworking crafts of Eastern Europe. I have, as David W. suggested, always read/heard it refereed to in the contemporary parlance of North American timber framing as a:

Diminished Housed Tenon

My concern (perhaps rooted in those same concerns as others have shared thus far?) would be not knowing and/or understanding the application parameters of the entire project?

One principle concern with this form of housed joint (loaded vertically as it is present for floor joists!) correlates directly to the degree of outward thrust it places on the supporting member. Because of the "wedging effect" it has within the given geometry the supporting member has to either be robust enough to withstand this thrust, or have a buttress and/or supporting architecture behind it to withstand these forces. The other, and what seems to be common in historical and/or present versions is a "tying member" in close proximity to the area of this type of joint, thus allowing the tying member to be of less mass as in your case.

Good luck with your project...It sounds fun!!! Let me know if I can expand on anything?

j

Re: What kind of joint is this/am I an idiot? [Re: MaxHardcastle] #34700 08/11/19 07:16 PM
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Roger Nair Offline
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Diminished Housed Tenon??? Please, call this something else, if anything it is the opposite, increased yes, tenon no (full section), housed no (no level bearing) and a slip through notch (not a fixing joint)


In the normal sense, diminished haunch, tusk tenons and soffit tenons have first lower down a lengthened penetration to provide a strong level bearing, second the diminishing length provides re-enforcement of the bearing while decreasing the cutting away of the receiving timber. This is especially important in maintaining bearing capacity in the beam that is notched to carry the joists.

One other thing, normally joists are tying members, if your joist fails to tie a frame then your joist is failing at a primary task.

Last edited by Roger Nair; 08/11/19 07:22 PM.
Re: What kind of joint is this/am I an idiot? [Re: Roger Nair] #34701 08/11/19 09:57 PM
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Jay White Cloud Offline
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Originally Posted By: Roger Nair
...Diminished Housed Tenon??? Please, call this something else ...


Sorry, as David also suggested, that is the descriptive term employed as I understand it, have heard it described and seen. I don't make the the rules or vernacular semantics, nor the syntax in English...LOL

Originally Posted By: Roger Nair
...if anything it is the opposite, increased yes, tenon no (full section) ...


A "tenon" ("Hozo"...in Japanese as just one example) can and often is "full section" and again from a perspective of timber framing historically and accross its vast cultural implications "tenons" do not have to be just a proportional element of a timber...they can be just the end of it, a "free component" of another member or a number of modalities still falling into the understanding of there given role as they play within context to the cultural practice of a region timber framing methods.

Originally Posted By: Roger Nair
...housed no (no level bearing) and a slip through notch (not a fixing joint)
...


Respectfully Roger, a "housed joint" does not nor is historically always a "level" bearing surface. Not in European or any other timber framing culture that I know of by definition.

It is...a trapping and containment of a the primary joint often employed to not only compensate for irregularity in the receiving timber, but also to resist further the tectonic loads a joint will sustain during its given service life within a frame...

Though this type of tenon is a drop in service member (in this case a joist) it can more than work if employed properly and bear loads effectively, but I would agree not as effectively as some of the other offered more advanced and less common methods as suggested. This is (as the OP described in his query) more often an in situ repair method and/or augmentation to work in concert with other tying members to be fully effective.

Originally Posted By: Roger Nair
...In the normal sense, diminished haunch, tusk tenons and soffit tenons have first lower down a lengthened penetration to provide a strong level bearing, second the diminishing length provides re-enforcement of the bearing while decreasing the cutting away of the receiving timber. This is especially important in maintaining bearing capacity in the beam that is notched to carry the joists...


In general, I fully agree with portions of that description of these types of tenon and there application.

They are however, the exception to normal practice, practical and/or common employment for joist which typically are just a "dropped" in full dimension "tenon" on the end of a joist...or...with a reduction to the joist in depth to reduce further the size of the mortise in the receiving member. In lesser forms of historical examples (often with splits and failures) this is a simple notching, but often in the better forms a adzed or drawn reduction accross the joist depth. Summner (or Summer, etc) beams this can be often found also...again a tenon and again full dimension.

Originally Posted By: Roger Nair
...One other thing, normally joists are tying members ...


Statistically...not true at all. Neither accross Europe, nor in Afrcia, the Middle East or Asia.

In actuality accross the breadth of the timber framing, joist seldom play much of a any significant role beyond bearing support within the floor diaphragm contextually and any moment resistance they offer or do play a part in is through frictional load forces alone...This, of course, is not always the case, and there are (as you mentioned) forms of joist that can and do play a role as tying members within the floor diaphragm of a frame.

If I had to guess and/or estimate, if an actual inventory of all members play the service role of joist within timber frames are accounted for...over 60% of them (conservatively that I have examined in North America or globally) most are like the "Neda" (or Nebuto ?) of Japan (et al) and simply rest atop the receiving member only...No joinery of any kind at all...just gravity...

Last edited by Jay White Cloud; 08/11/19 10:01 PM.
Re: What kind of joint is this/am I an idiot? [Re: MaxHardcastle] #34702 08/12/19 02:11 AM
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Roger Nair Offline
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There is of course the Guild's timber frame glossary by Ken Rower

TENON. The end of a timber, reduced in section and flanked by one or more resulting shoulders

HOUSING. A shallow mortise or cavity to receive the full section of a timber end for load bearing. Often but not always combined with a standard mortise to add bearing area and secure the connection via the tenon.

Frankly Jay, your snowjob misses many obvious points. But to make claims of comprehensive knowledge of the building systems around the world is anti-intellectual.

Last edited by Roger Nair; 08/12/19 02:12 AM.
Re: What kind of joint is this/am I an idiot? [Re: MaxHardcastle] #34703 08/12/19 02:16 AM
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timberwrestler Offline
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I'm not quite sure what you're looking to accomplish. But if you want to even skip the joinery, you can just sit the joists on a 1.5" wide ledger, and that'll work just fine. No hangers needed.

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