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Jack studs and headers

bhackford's picture

I was reading code check last night and was wondering if double jack studs are needed for 2x12 headers spanning 36"? The code reads all 2x12 headers need double jacks???? In practice they only one because jacks are determined by span not header size right? So, only one jack each side is need, right.

Thanks

(post #96509, reply #1 of 40)

Out here on the left coast, you only need one trimmer (jack stud) on each side of an opening up to 6'.  Over 6' you need double trimmers on each side.  Hope that helps..RZ

(post #96509, reply #2 of 40)

Headers are determined by span and amount of load it must carry. ( i.e....roof only....roof plus 1 floor only...roof, ceiling, 2 floors only...etc).


You need to consult a regular header span table to determine what size header is correct for your situation. These tables also dictate the number of jack studs needed for each situation.


Generally speaking, for most loads, a header composed of doubled 2x4s usually can safely span somewhere between 30 " to 40" depending on loads.... dbl 2X6s fall in between 3ft - 4ft; depending upon loads.  Doubled 2X12s are usually used for longer spans ( 6ft - 8ft ).


Doubling up on jack studs is the norm when supporting headers composed of 2x8 stock  or greater...sometimes you need to double up jacks on 2x6 headers as well...it really depends on length of span and load it is carrying combined...both factors ( load & span) play an important role in this detemination. 


 The more bearing surface the header has to rest upon, the more solid ( stiffer) it is. Since bigger stock is used for heavier loads, having a larger "perch" to rest upon helps to keep the header from crushing under the heavy concentrated point load at each end...hence the requirement for doubling up the jacks.


If the main reason you are using 2X12s in a 3ft span is because you wanted  to avoid using cripple studs, then I would think using a single jack stud in this particular situation  is OK if the existing opening could have been safely spanned with a smaller header that would have only required single jacks...otherwise, if you need this 2x12 due to really heavy loads, use a double jack.


Just my opinion...and that doesn't mean I'm right cause I'm not a framing expert...though this is how I've handled the situation in the past....though I must tell you, that most times ( almost always) , I lean toward "overbuilding" and as long as I have the room to put in another pair of jacks, I usually do....$5 for the 2 extras buys me a lot of peace of mind .


Davo

(post #96509, reply #3 of 40)

Jack studs transfer vertical loads from top plate to header. Header transfers vertical loads laterally and then down to bottom plate via cripples and jamb studs. If there was no opening there at all, single studs would directly transfer vertical loads from top plate to bottom. What's the difference? Occasionally I have seen engineers spec double cripples and/or jamb studs, but this would be for cases where there are particularly heavy point loads. Jack studs are simply to diffuse the vertical load and transfer it to the header


Looking at the code book I have (Canadian Building Code 1998), this is their wording:


"... studs shall be doubled on each side of openings so that the inner studs extend from from the lintel [header] to the bottom wall plate and the outer studs extend from the top wall plate to the bottom wall plate."


What they are talking about of course is cripple and jamb stud; perhaps the wording in your code is similar enough to make you think that the jack studs were to be doubled.


Why 2x12 header for 36" opening anyway?


Wally


Lignum est bonum.

Buccaneer Contracting

Penticton, BC

(post #96509, reply #4 of 40)

Sly,


Check your terminology...


"studs shall be doubled on each side of the openings so that the inner studs extend from the lintel (header) to the bottom wall plate and the outer studs extend from the top wall plate to the bottom wall plate"


The "inner stud" is usually called a Jack stud, or even called a Trimmer stud. The "outer stud" that extends unbroken from top to bottom plate is usually referred to as a King stud.


 


Cripple studs are  actually the short studs that are placed above a header or below a window sill. Jamb studs...no such animal; though I think you are referring to the King as a "Jamb" stud. 


You are correct in that a header does transfer a vertical load laterally across its path. But, the header must eventually transfer this load downward toward the bottom plate...(the header's load doesn't stay in lateral limbo) . The studs that absorb this downward flow are the King stud and the Jack stud, not the cripple.


Jack studs don't just diffuse the load to the header...quite the opposite, the header is diffusing the load to the Jacks. Which is why when you open up a load bearing wall and install a header to span a certain length, you have to make certain that the floor below has proper support in the same location as the Jack and King studs.. If not, you have to beef up that area directly below with  either a column support of some type,  or wall or whatever.


Davo

(post #96509, reply #5 of 40)

If you substitute "jack" for "cripple" and vice versa, Sly's message is right. I think you were saying that, but in a more round about way. ;-)

(post #96509, reply #11 of 40)

Looks like we are victims of regional differences in terminology. In western Canada, these are the definitions:



  • cripple: vertical member directly supporting a lintel (header); "inner stud"

  • jamb stud: full-length vertical member closest to opening; "outer stud"

  • jack stud: shorter studs located between lintel and top plate

So if you read my post applying the terminology I'm used to, you'll agree that there is indeed no need for doubled jack studs! However, I can see that it must looked confusing!


No requirement in our code for doubled studs supporting bigger headers, but not uncommon to see engineers spec this, even triples where point loads are very heavy. Also may see doubled jamb studs (king studs) called for.


Wally


Lignum est bonum.

Buccaneer Contracting

Penticton, BC

(post #96509, reply #13 of 40)

Those definitions are backasswards from anyplace I have ever worked in the States. You got a source for that definition?

 

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(post #96509, reply #14 of 40)

Yer on a roll tonight, eh Piff?  Just cleanin up a little?

(post #96509, reply #15 of 40)

Somebody's gotta keep the home fires burning until you get your flaming butt back in here.

;)

 

 <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #96509, reply #16 of 40)

When I went through my apprenticeship those were the terms used, they are certainly the common usage in the workplace. The only one we see a bit of difference is on the jobsite we refer to headers whereas at school and in the code the term used is lintel.


Don't have my text books at hand as I lent them to one of the apprentices while he is at school so don't have title and author for you to look at right now.


Wally


Lignum est bonum.

Buccaneer Contracting

Penticton, BC

(post #96509, reply #17 of 40)

Sly,


I understand what you are saying, but honestly, every text book I have on carpentry does not list the terminology... or rather the definitions...that you have given. I'm sure you know how to build, but the terminology you are using must definately be regional  for your location...nowhere in the STATES do we use those phrases the same way you are using. That's why I commented in the first place...I felt most inexperienced carpenters would be confused after reading your thread.


BTW in my area the word "lintel" is  only used when referring to  the use of either a piece of steel ( when building a brick /stone home)   or  a concrete bond beam (when building a concrete home)  when heading off such openings. Any  framed opening where wood is used is always referred to as simply being a "header." 


Davo

(post #96509, reply #18 of 40)

I'd have to agree, even in my amateur experience, "jack stud" and "cripple" are interchanged relative to the above definitions.


Of all the preposterous assumptions of humanity over humanity, nothing exceeds most of the criticisms made on the habits of the poor by the well-housed, well-warmed, and well-fed.  --Herman Melville

(post #96509, reply #34 of 40)

are interchanged relative to the above definitions


I also remeber being taught on the job site that under the window sill are the jacks, to the bottom of the header were the queens, and all the way up to the plate were the kings; cripples only existed between header & top plate.


That's the better part of three decades ago, and being taught by a fellow who was in his sixth decade as a carpenter.


Occupational hazard of my occupation not being around (sorry Bubba)
I may not be able to help you Occupational hazard of my occupation not being around (sorry Bubba)

(post #96509, reply #35 of 40)

Although, thats not exactly the nomenclature that we use....yours just seems right.  It makes logical sense even though I've never heard of any framing member being refered to as a "queen".  Now there's been a few framers that I've refered to as queens, but that's a whole other story...... ;)

(post #96509, reply #36 of 40)

been a few framers that I've refered to as queens, but that's a whole other story


LoL!


No body could ever tell me where the "ace" and "ten" studs were framed--even at young age, I knew better than to try and draw 2 cards into a straight . . .


Occupational hazard of my occupation not being around (sorry Bubba)
I may not be able to help you Occupational hazard of my occupation not being around (sorry Bubba)

(post #96509, reply #19 of 40)

Hey, what can I say? That's the usage here that I trained under. I know 'lintel' has English background, I guess that's part of the Canadian landscape. I grew up in Australia where they also use lintel rather than header. LOTS of different terminology to learn coming to Canada.


So what was the outcome of the original question, anyway? Do you need to double up the inner studs supporting a 2x12 header?


Wally


Lignum est bonum.

Buccaneer Contracting

Penticton, BC

(post #96509, reply #20 of 40)

"So what was the outcome of the original question anyway? Do you need to double up on the inner studs supporting a 2X12 header?"


 


Answer...Yes...so long as a 2X12 is actually needed due to loading. On page 83, Table R502.5(1) of th 2000 edition of the International Residential Code, a chart is found which lists the appropiate header size needed to safely span a certain distance. In every aspect where a dbl 2X12 header is listed, the number of required jack studs are listed at 2 for each end of the header.


Sly, I'm sure you are well aware that a lot of times, when framing for 8ft tall walls, a framer might use 12 inch header stock so as to avoid cutting and nailing a bunch of cripple studs that would be situated between the top of the header and the bottom of the top plate.   Although a 3FT wide door would normally not require such a beefy header, due to simplicity of framing and production speed, a 2x12 header may be utilized. In cases such as this, under simple normal loading, the header would not require doubled Jack ( inner) studs; because the loading does not demand it. 


 However, if this 3FT opening was  instead a door cut through.... say, a concrete basement block wall, and this opening was load bearing and supported a couple of floors, plus the roof, and the ceilings, then if it was determined that  2X12s be used to safely carry the aforementioned load, then doubled Jacks ( or possibly triple Jacks) would definately be required.


So the long answer is...it reallys depends on the loading. The IRC is assuming that 2X12s are only being used when actually needed and therefore require the dbl Jacks in their charts and directives...but again, they are assuming that due to loading configurations, the contractor has to use 2X12s to safely carry such loads...when such is actually not the case, then dbl Jacks are not neccesary.


At least, that's my take on the scenario.


Davo

(post #96509, reply #22 of 40)

I had never heard the terminology used like that either, although I'm "OK" with the useage of the word lintel. 


BTW a guy I know who lived in Austraila told me they studded their walls with "4be2s"  :-)    


Matt
Matt

(post #96509, reply #24 of 40)

4be2's!!! I love it, guess what new word I am using Monday on the job!

(post #96509, reply #25 of 40)

Here in Chi town area 12" headers up to 8' single trimmer on each end. The trimmer is universally called a cripple here. When laying out the plates X for studs C for cripples or more properly called trimmers.


Never serious, but always right.

Never serious, but always right.

(post #96509, reply #30 of 40)

Yep, and blocking is known as noggins.


What's in a name indeed!


Lignum est bonum.

Buccaneer Contracting

Penticton, BC

(post #96509, reply #31 of 40)

Well, Boogerin' with Blue wouldn't be the same thing in some countries. Blue might find himself boogered there.

 

 <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #96509, reply #32 of 40)

'course old Blue wouldn't need to know the name for blockin'

 

 <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #96509, reply #23 of 40)

Let us face it we should all know by now that framing has different names for different locations. I have seen guys get a little bad tempered over terminology on a job site. I don't understand it, nothing to argue about.


As a second year apprentice I was working with an Irish jouneyman, I mentioned "toenail" he stopped me in my tracks and indignitly asked that I repeat what I said, he told me in no uncertain terms that I was to call it a "stitch". Thirty years later I still call it a toe nail.

(post #96509, reply #37 of 40)

Different question - same subject. What does everyone think of putting headers up in the floor structure above the span. What I mean is throw in extra stock against the rim joist/band joist/rim board (whatever you want to call it) over each opening. For example, 2 story house, 1st floor exterior wall has a 38" window r.o. I put a single or double 2x6 on the flat over the r.o. with a king and a jack plus cripple on each side. In the floor framing above I install the rim board plus two 2x10s or 12s...by 50". If a joist runs into this header I use a hanger.

This seems to me to be much faster framing, a more integral wall system (against racking), more air tight header and I'm sure I saw it in one of the magazines.

(post #96509, reply #38 of 40)

Mark, we often use "flush" headers, although not very often in the manner you describe. Structurally, your idea is sound and if viewed from the insulation perspective might acuatlly be better. Also, it gives the greatest flexiblity for moving windows up or down. It seems faster too!


Now your peaking my interest!


Two drawbacks: it's unconventional and you'll take heat from those that don't like it's appearance and it won't help hold up a brick lintel, if the lintels were supposed to be bolted to it (they never are on short spans like that).


I wouldn't like the idea of putting hangers on, and that wouldn't work well on our usual plans that require us to cantilever the deck past brick.


I like the idea and will look for situations that it may be helpful.


blue


Warning! Be cautious when taking any advice from me. Although I have a lifetime of framing experience, some of it is viewed as boogerin and not consistent with views of those who prefer to overbuild everything...including their own egos


Additionally, don't take any political advice from me. I'm just a parrot for the Republican talking points. I get all my news from Rush Limbaugh and Fox and Friends (they are funny...try them out)!

"...

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From the best of TauntonU.

(post #96509, reply #39 of 40)

Funny this should come up; we have just done a bunch of openings in the project I'm working on. They must be structurally sound as they are in shearwalls and the engineer and TJ tech both went with them.


This building has a crawl space with four framed bearing walls inside the foundation walls. Naturally we have to provide openings to allow access to all parts of the crawl space, but to do so would mean 2x10 headers over said openings. The underside of floor joist is only 3' above the concrete rough coat, so a standard header would reduce that height by another foot. Crawl spaces are hard enough to get around in already without having to squeeze through a 2' high doorway.


So the engineer and TJ guy spec a flush header. Wherever there is an opening below, a piece of 1.75" LSL rim board is toenailed along the 2x6 wall centreline, and the TJIs are installed in hangers. Studs at the dge of openings were doubled up. Because these are shearwalls, the framing is sheathed on one side as normal. This system was used in the full-height shearwalls on the main floor as well.


So now you know, engineers do approve this system (in BC anyway).


Wally


 


Lignum est bonum.

Buccaneer Contracting

Penticton, BC

(post #96509, reply #40 of 40)

Mark,

The only reason we'll put flush headers in is when we have tall windows with circle tops or transoms on exterior walls and on interior walls when we frame for arches. Then you just nail the joists in and put hangers on them. Other than that there's really no need to put flush headers in and hang a bunch of joists unless you need the room. We also double up the box on top of the foundation where there's a window or door opening and install hangers.

Our 8' precuts here are 92-5/8" so if we're using them most of the time we'll need to put in flush headers when doing what I described above. If we're framing with 9' precuts or 10' precuts we can get away with putting headers at rough opening height.

Joe Carola


Edited 11/10/2004 7:29 am ET by Framer

Joe Carola

(post #96509, reply #6 of 40)

>> The code reads all 2x12 headers need double jacks <<


IMO, if you want to read what the code says get yourself a real code book.  The one for your state, assuming you are in the US, or the one for whatever area you live in.  Personally, I don't find those generic type books of any use as they can't give specific information for your locality. 


That said, maybe the Code Check's assumption was perhaps that a 2x12 header was required in the specific situation because of loads above it.  Say, for example, if there was a flitch plate flush beam that landed above a 36" opening.  Then, 2 jack studs (or more) might well be required on each end of the short 2x12 header.


2 questions for everyone else out there:


1) Are there any full time building professionals out there that actually use one of these generic Code Check type books to make decisions on your projects?


 2) In Canada, does each Providence have it's own set of building code standards, or does the entire country adhere to the same code, or is it perhaps even administered on an even smaller geographic scale like per city, per town, etc? 
 


Matt
Matt

(post #96509, reply #7 of 40)

While providence does play a roll in construction in Ontario, the larger municipalities have building codes based on the provincial code. Municipal codes can require items additional to the provincial code.

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An ex-boat builder treading water!