what’s the rule of thumb for how many jack studs to use for 2 ply 2×10 headers. At what point to you have to go from 1 each side to 2 or more each side?
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When the load gets heavy enough.
Not the answer you're looking for, huh? FWIW, I double jacks on most all RO's over 6' whether spec-ed out or not.
Good idea. Doubling up probably increases the wall's ability to carry a load while it's being racked by an earthquake. There's less chance of the header shifting off its support. There's more nailing surface for shear resisting ply/osb sheating.http://costofwar.com/
sounds like good answer to me. generally speaking though, as far as you know, most codes only require 1? If more than one is noted it is done so by an engineer?
IRC requires 3" bearing (2 jacks) at 6' or more.
thnks for info...cheers
I don't claim to be an IRC expert, but it seems strange that it would require double jacks when floor joists are only required to have 1 1/2 bearing... (3" on masonry) - unless of course the purpose of the double jacks is to prevent deflection from the load. If that's the case, wouldn't double king studs accomplish the same thing?
Edited 9/7/2005 10:07 am ET by Soultrain
I'm certainly no expert either... A 6' header carrying the dead weight of the wall/roof/snow above it in addition to 4 or 5 of the next floor(s)joists with their respective dead and live loads though, is a lot more weight than a floor joist is asked to handle. Now, on a header that is parallel to floor joists, I have no idea why the extra jacks would be necessary for a 6'1" opening...I'm sure someone else knows tho...
Actually Soultrain, you are on the right track.
I was trying to stay out of this thread because I'm quite certain that most would scoff at what I do.
I tend to only double the jacks when I see a huge load. I don't put as much credence on length, as much as load.
I also know, from conversations with engineers regarding this issue that doubling the king stud is as important as adding jacks. I remember having to put SEVEN(!!!!!!!!) STUDS under one load point on a Pulte house. Since the wall was perpindicular to the beam, only 3.5 inches were actually under the beam. All the rest was just hanging out and stiffening the studs to keep them from bowing.
I also worked for one particular builder who tended to overenginieer everything. They always specced out each header that required extra studs at the bearing ends. We specifically asked the engineer whether he wanted extra jacks, or extra king studs and he told us that he wanted KING STUDS! So, when a header called for three studs at the end, we would put two kings and one jack. Often these were 8' headers.
Nothing I've built in the last 30 years has fallen down to date.
blue
Hi Blue. Can you explain to me why you'd have two kings and only one jack? I don't get it.... what am I missing. I've only seen that specified on drawings once, and when I asked the builder about it, he told me to double the jacks and use a single king. Made sense to me, but I'm guessing we missed something.
2 years on my own.... everything still standing here too! ;)
I called my architect this morning (because I have a 6 foot wide opening for a patio door that carries another floor above & the roof). He said the purpose for the extra jacks is to prevent deflection. It has nothing to do with increasing the load bearing surface. He said that extra kings accomplish the same task.
Thanks for the 411. So I wonder if it matters whether they are jacks or kings as long as the end result is three 2x's? Suppose it depends on the situation. Guess I'll just keep following the plans!
two reasons for more kings rather than more jacksThe main thing the extra meaat is doing is preventing deflection. Take a perfect piece of lumber and it will take a whole lot more weight on a 2x2 that on a triple 2x4 full of knots, checks, and twists. I would tend to think that engineered post lumber should take more than typical framing lumber can.
I'm sure you know that oncce an overloaded stud starts to deflect, it will keep going until ... - but I'm talking drastic overloadsSo either an extra king or jack can help with that, but since the king goes plate to plate, it is less likely to telegraph its stresses to the drywall corner joint - you know that one that shows a crack in the finish so ofen? ( mostly, that crack is from header material shrinking when it dries, but not always)The only reason that the jack might be more preferred for doubling is when considering shear - bbut who amoung us has ever seen the end of a joist or header shear off? I've seen some serious compression there when there was other failures and/or rot going on thoughAnyway - the main reason i stopped back in on this thread is that I was thinking about another factor, that being when you are framing with 2x6 instead of2x4
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The code check book from Taunton doesn't differentiate between 2x4 & 2x6 framing. Do you know if the IRC book does?
My latest codebook is from about 1976 and I don't even know where it is.
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IRC does list 2x4 and 2x6 walls and what they can be used for, ie 2x6 for 2 story house, but doesn't seem to specify anything as far as jacks/kings go. I'm thinking that this is one of those areas that the code book has purposely simplified for ease of use. However the header table does list tripple and quadrupple 2x headers, which would have to have a full width jack so in a way it does address wall thickness somewhat.
Would a mid-span block do as good a job of preventing compression deflection of the king? I understand that preventing deflection is crucial to the wall system's integrity.
Doubling kings would likely also help minimize jamb opening twisting and other problems that drive door hangers crazy.
Some mind wanderings here that I want to run by you and others:
I'm thinking that overhead loads are transferred by cripples to the header. However many jacks bear the header's load, the jack(s) receive these over a faily small bearing area. The greater that bearing area (i.e. the more jacks there are), the more easily a properly sized header can do its job of transferring loads horizontally back to a sturdy vertical load path. So long as the jacks don't deflect of course.... ergo use a mid-span block instead of a doubled king???
http://costofwar.com/
Edited 9/7/2005 10:42 pm ET by Pierre1
I have to confess that I have no idea what you mean by a mid-span block. Maybe I have a mental block, but all i am picturing is a post in the middle of the openning span.
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My error. Not mid-span, but mid-height, like fire-blocking.http://costofwar.com/
gotchaq and you be right
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Pierre1 the blocks the you refer to, I have heard called "girts" and are called for in walls 10' or more in height.
Girts are (also) a timberframe building method where a wall structure (built with load-bearing components, and complete with sill beams for each floor) is assembled flat on the ground then raised as a whole. A girt will run the full length (or width) of a building.
A wide building might have three parallel girts. Connecting beams and floor/ceiling joists connect these girts to each other, completing the structure's lattice.
WRT the OP's concern - and the ideas raised here by others - my suggestion is that blocking will help prevent king stud deflection where point loads are substantial. Also useful as fire-blocking where the studs are 10' or higher, as you suggest, or to bring bowed studs to their o.c. layout.http://costofwar.com/
....but before that, they all fell down.....
Project we were on a few years back the Engineer called out 3 jack studs on the 16'x7' garage door opening.
Jack studs vary according to plans. At times they may require more than one on each side of the R.O. However, personally I double them up on any rough opening greater than 60 and less than 80. I triple them on anything from 80-108, and for anything larger, including garage doors, I quadruple them. As for codes, they are the bare minimum requirements. I always try to "beef" everything up if possible.
Ocean State Builders, Inc.
Wilmington, NC
Fine Custom Framing and Exterior Trim
great info guys.... thanks
I get suprised at how many frmaers never even consider his question. Like Brian, I double them at 6' but there is more than width of openning that impacts on this. Whether it is a one, two, or three story house, and how those loads transfer to foundation has something to do with the decision too.
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My rule of thumb is to check the chart in the IRC book that is in my truck.
You thumb through it untill you find the answer eh?
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I was looking in my local code book and couldn't find a chart, so I thought I'd ask. A chart would be nice. But so far everyone has confirmed what I was going by. But it's nice to get feed back to see if you're on the right track.
I follow the NYS code. Table 501 - depends on the snow load and the zip code.
When in doubt, I add a stud. If I think two is almost enough, I throw in three. If it was up to me, walls would be solid studs nailed together. Just kidding, I would put in windows and doors too.
If the header is Doug fir, theoretically a single jack should be good for a load of 3280 pounds, provided that it's secured against bowing by the kings. The limiting factor is compression perpendicular to the grain. On my house, I kept it under a ton per jack stud. When you get into loads that require multiple jacks, it's important to think through the rest of the load path, all the way down to the dirt.
-- J.S.
Er...uh... I didn't intend for that last response to sound smart-alick, but after rereading it this morning it might have inadvertently come across that way. I literally don't frame often enough to come up with a decent rule of thumb for headers and jacks so I must consult a smart book. (isn't framing just a necessary evil to get to the finish work? ;-) I have a hard enough time remembering the applicable chart is in the floor section let alone what's in it.
Ok, I ran out to the pickup and have the IRC 2003 in hand. Going to the "floors" section (don't ask me why the chart isn't in the "walls" area) it looks like we have 2 snow loads, 3 building widths, 11 header dimensions, and 7 supported loads to choose from in table R502.5(1) Girder Spans and Header Spans for Exterior Bearing Walls. Hmm......30 psf snow load, 20 ft. building width, roof and ceiling only, #2 doug fir-larch/hem fir/spruce-pine-fir....hmm....lets see....it shows 6'10" (only 2-2x8 header required) as the last entry requiring only one jack. Go wider, more snow load, more than a simple roof, or a wider roof span and you'll need 2 jacks--at least with a doubled 2x header. With the above conditions it says a 2-2x10 header will span 8'5". With 50 psf snow load the span drops to 7'3" and add 8' to the buildings width and you lose a foot of span--6'3". If you add a second story to the wider building you'll be down to 5'1". More load than this and 3 jacks are required.
Personally, this chart seems to be one of the most useful in the whole shooting match since it answers most header span questions and it would be the first two pages I'd photocopy (if that were legal of course).
Hope this helps, Don
Some good examples there.
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Piff, while I under stand the theory of preventing deflection, I'd have to guess that the sheathing (and nails) does a pretty good job of preventing deflection as well, no?
Just kicking things around regarding the topic.... not trying to argue anything, just trying to look a little closer.
Probably.What you said gave me a flash of understanding what Pierre might have been saying too. his "midspan block" might be stud space blocking halfway up in the wall? and yes it would fight deflection from extreme loads too.overall, I think this is one place where we probably overbuiiold as far as structure is concerned, but ANY movement here shows itself critically in the trim and finish long before it will fail structurally so to have a good looking finish, we have to overbuild in the structure.I ain't arguing either, just thinking it through
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"Personally, this chart seems to be one of the most useful in the whole shooting match since it answers most header span questions and it would be the first two pages I'd photocopy (if that were legal of course)."It is absolutley legal.It what you do with the copies that might be a problem.For example if you want to staple a copy to each set of house plans that you are working on that would be fine.If you setup a stand selling copies that would be a problem.
Post that puppy here...file sharing put to good use!!!!
And occasionally, a concentrated load such as a beam or girder truss somewhere above the opening will dictate more square inches of bearing surface under the ends of the header. I once had a 5 1/8 x 13 1/2 header called out for a 30" opening in a daylight basement. I think a roof beam posted down over the opening.
How Many Jack studs
I am by no means a framer or professional builder but I was told by a framer here in Indianapolis that a good rule of thumb for jack studs is to use as many jack studs as there would be wall studs had there not been an opening, or just under that amount to the nearest even number. Say I had an opening where I cut 7 wall studs I would use 6 or 7 jack studs. Thus 3 per side in the opening. Since your wanting to support 7 studs that were cut.
dooley
I'm just over the border in Ohio and I've never heard that one.
nor would I even think it real. I would suppose there might be a point load above where something like that would be remotely possible.......................but have never framed it.