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Any device to meet 2-jack stud req't with 1-jack?

Posted by la_koala (My Page) on
Thu, Oct 28, 10 at 21:20

OK, I'll lead with the question and whoever wants the gory details can read further. :-)

Question: If the table in the residential code says a wooden header needs two jack studs, is there any device to use that meets code and have only one jack stud?

From what I've read in this forum, there are "header hangers" that could be used for some situations. But are those only for reducing the need from one jack stud to no jack studs?

What about using another header material (like LVL) vs a wooden header?

Thanks in advance for any educational information about this!

Note: I'm 'just' the homeowner, and I'm not planning on doing any of the construction myself. I plan to hire a GC for the work, and would hire a structural engineer to review the final plan if you think one is necessary here.

My goal of asking this is to prepare myself for the 'worst' case of where the windows will likely end up positioned in the wall, so I don't fall in love with some other idea before encountering the reality in the field after the demo. :-)

Here are the gory details:
- Nice view is directly opposite the back left corner of the house. (Kitchen)

- House has full basement, three full floors, and then the attic space (under the peaked roof) above the 3rd floor. Wood construction.

- The house is basically a rectangle with peaked roof (roof line runs parallel to the street) with central staircase. Two rooms on every floor on either side of the staircase.

- In the kitchen, there are two double-hung windows (glass size approx. 30" wide). They are each symmetrically about 45 inches from the corner: one in the side wall and the other in the back wall.

Picture the corner of the room, then a blank space of wall going horizontally about 45 inches from the corner, then a double-hung window--in both the side wall and rear wall.

Now, I'm going to have the kitchen remodeled anyway--gut remodel, new electric, plumbing, layout, whole enchilada.

My thought is to replace each of those double-hung windows with factory mulled two-double-hung combination windows.

But I also want to have as much daylight opening as possible (to see the view).

So, my ideal "picture of success" would be to get both of those combo units as close into the corner post as the Building Code and physical reality allow. And have as wide a window unit as possible. :-)

Imagining a 68 inch rough opening then, to have one jack stud on each side, that's a 71.5 inch header, right?
(to span the jack stud on each side; 71.5 inches is almost 6 feet).

If I look at the code for here (MA), the current one seems to be based on whatever is before IRC 2009. (I say that because the one that's in public hearing now is based on IRC 2009). Current MA residential code is 7th Edition (link below).

The relevant table seems to be on p. 601:
780 CMR TABLE 5502.5(1)
GIRDER SPANS AND HEADER SPANS FOR EXTERIOR BEARING WALLS
(Maximum spans for Douglas fir-larch, hem-fir, southern pine and spruce-pine-fir and required number of jack studs)

Reading this table, it seems to be:

- For a span of 6 feet and ground floor snow load of 50 psf, and a 28 width house, this header is in "2 jack stud land".

Hence my question: is there any device (hanger or LVL header or something) that would not require 2 jack studs on the side of the window unit at the corner of the house?

That would allow the window frame jamb to be as close to the corner post as possible--at most one jack stud?

I know I've glossed over things in the table like the center-bearing floor/clear span floor: all of the relevant rows in the table seem to be pointing to at least a 2-jack stud situation regardless.

You who made it thus far, thanks for reading all of this!

Here is a link that might be useful: MA 7th Edition One and Two-Family Dwellings


Follow-Up Postings:

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RE: Any device to meet 2-jack stud req't with 1-jack?

An engineer can come up with a way to cantilever the beams so that no corner post would be needed at all, but it's a larger job than plopping in a new header. Code in cases like this are more like guidelines; if you can get a stamped set of drawings from the engineer, and it's built accordingly, there's nothing the inspector can say other than "passed".

Casey


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RE: Any device to meet 2-jack stud req't with 1-jack?

Hi Casey,

Yeah, if I could build the house from scratch, no corner post would be lovely. But I'm not that rich. ;-) I think I can live with the post. I just hate to "lose" another width to a second jack stud along with the one jack stud and the window frame jamb width.

I'm curious about this sentence: Code in cases like this are more like guidelines; if you can get a stamped set of drawings from the engineer,....

What about this situation makes it a "case like this"? Is there some leeway in this situation about the header/stud combinations that wouldn't be in some other situation?


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RE: Any device to meet 2-jack stud req't with 1-jack?

In some circumstances, a steel header hanger can be used to replace the jack posts.

Convey your concerns to the structural engineer so he can design the best solution in accordance with your Code. I've found that with any concern I've had, the engineer has seen it many times before.


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RE: Any device to meet 2-jack stud req't with 1-jack?

"Code in cases like this are more like guidelines..."

The code is the minimum 'per se' structure that will pass inspection.

If you follow the code rules the structure passes.

Try to alter the rules and the AHJ can demand you have stamped off plans (engineer or architect) that show the changes meet the requirements for loading given in the code.

It can be anything from simple load calculations to a real PITA for structures that vary significantly from the 'norm.'


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RE: Any device to meet 2-jack stud req't with 1-jack?

I'll bet that a microlam 1.9E could be used and the 2 jack reequirement tossed. Peek at these tables:

http://www.dickslumber.com/lumber_wood/documents/Microllam.pdf

Not spam, I just have this saved in my favorites as we have a 20 footer in the remodel.


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RE: Any device to meet 2-jack stud req't with 1-jack?

If you look at note d below the table it says: "Where the number of required jack studs equals one, the header is permitted to be supported by an approved framing anchor attached to the full-height wall stud and to the header."

In Massachusetts, any structural element that is not prescribed in the one & two family building code must be designed and stamped by an engineer (not an architect). That requirement applies to an LVL but most lumberyards can get the LVL manufacturer to provide the stamp and that might include a smaller bearing or a larger hanger device.

A Simpson RTC44 might accomplish what you want to do.

Here is a link that might be useful: Simpson RTC44


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also

The header span is the same as the rough opening of the window not the length of the header member.

If your exterior wall consists of 2x4's you would need 3 jack studs for a wall supporting two floor and roof rafters; 2x6 studs would require 2 jack studs.

If there were no jack studs the two window frames would obstruct each other. If there were two jack studs 3+/-" trim would fit against each window.

Another consideration is the required lateral bracing of such a tall house. Since the corners are the best place to resist lateral forces, the engineer might have to create some shear walls elsewhere.

It is not wise to design one small part of an exterior wall without considering the entire house frame. Start with the whole and work toward the parts or hire a professional.


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RE: Any device to meet 2-jack stud req't with 1-jack?

Thank you all for taking the time to respond here! I consider it a red-letter day when GW recognized experts like Casey, worthy, brickeyee, macv weigh in. And kaib, while I don't recognize your GW name, I appreciate the info from someone who's used one.

macv, you wrote: In Massachusetts, any structural element that is not prescribed in the one & two family building code must be designed and stamped by an engineer (not an architect). and It is not wise to design one small part of an exterior wall without considering the entire house frame. Start with the whole and work toward the parts or hire a professional.

I completely agree with the latter statement about being wise to hire a professional. What makes me nervous now is that I *have* hired an architect for this remodel. According to the MA license lookup, his license is current. However, in light of your comments and my own understanding (admittedly limited), I am concerned now that he hasn't thoroughly thought through this area of the remodel--and possibly has not consulted with a structural engineer on it.

Is this something a licensed architect ought to have picked up on? Or at least mentioned to me? He's been licensed for 10 years and working as an architect that long. His drawing has the two window units, each 2 1/8 inches width away from the corner.

(The 2 1/8 inches were put in at my suggestion to allow for that much casing--only because it balanced minimizing the width for the view and mimics what's done in the bay in the dining room at the front of the house. But this suggestion to the architect was aesthetic on my part--not structural. I am not an structural engineer, only fairly good at math and analytical stuff.)

This is a house built in 1884 in MA. I think the architect is assuming 2x4 studs in the exterior wall. While I do understand that in an existing structure, it's impossible to determine everything about the hidden as-is conditions prior to opening up the structure, I would think that if he is assuming existing 2x4 studs for the plan drawing, that he would have at least noted a 3 jack stud requirement for this header span.

I'll post an image of the latest plan drawing so you can see what I mean.

Thanks so much for all the great input!


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Portion of Kitchen construction drawing

Here's the clickable thumbnail to Photobucket. Please let me know if the pic doesn't display OK:

2010 Aug Kitchen Plan

What's the appropriate protocol to ensure I have the proper information? Do you think I should consult with a structural engineer on my own? Or request the architect to consult with one and I receive the report?

While I don't want to signal to the architect that I don't trust his expertise, I do want all the i's dotted on this.

I really appreciate all of the input. I'd rather any "bad news" now in planning then in the middle of construction. Thanks!


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RE: Any device to meet 2-jack stud req't with 1-jack?

I see 3 LVL's inside the house but I don't see the header or post sizes at the window. Where is this information shown? Your architect is responsible for designing every code regulated part of the work and showing it on the permit documents. If needed he would hire an engineer or ask you to hire one but you shouldn't have to ask. An engineer would be needed for the 3 LVL's shown on the plan even if that engineer works for the LVL manufacturer.

I will not design a house without an engineer and that rule has saved me from some serious problems. It's cheap insurance.

3 LVL's are 5 1/4" wide so the wall studs/posts under them must be that wide. These kinds of houses in MA usually have rough 1 7/8 X 3 7/8" studs so I guess the wall will be furred out 1 1/2" +/-.

So if the wall studs total 5 1/2"+/- then the post at the windows could be a 6x6 and it would not be difficult to satisfy the bearing requirement.

Also, it is unlikely that both headers hold up the ends of joists from the two floors and the roof rafters above (they would span in one direction or the other) so an engineer could design for the actual loads and reduce the header and bearing sizes. I'm not saying the architect doesn't know how to do that but in MA an engineer's stamp is required.


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RE: Any device to meet 2-jack stud req't with 1-jack?

Hi macv, thanks so much for taking the time to look at the plan pic, and for the thoughtfulness of your response.

On the current documents I have from the architect, there is no information shown about the header or post sizes at the window. All I see is a Window Schedule table and a note saying "Verify in the field" under Rough Opening.

I will add this whole area about the headers/support/wall furring/engineer to the list of discussion topics for my next meeting with the architect.

And this is wise advice: having an engineer "design for the actual loads". I think I might print it out and tape it on the wall as a constant reminder.

The hardest part of this whole process for me has been knowing who to ask what of, and what I 'should' or shouldn't ask about. It never would have occurred to me to ask "is that wall going to be furred out?" And yet it seems that would matter for measurements to order things like the actual windows, the kitchen cabinets, etc.

The post at the windows could be a 6x6 and it would not be difficult to satisfy the bearing requirement

Just curious: how does the post being a 6x6 make it less difficult to satisfy the bearing requirement? If the post is already existing in the house, what happens in remodeling construction--does it get notched and a new header fit into it?


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RE: Any device to meet 2-jack stud req't with 1-jack?

If the house really has three stories plus a roof above the window headers, you will probably need a new Parallel Strand Lumber (PSL) post at the corner and if the structural wall will be 5 1/2" thick (that's what appears to be shown on the drawings) then the post could be 5 1/2" X 5 1/2" and two 1 3/4 X 5 1/2 PSL studs could be attached to the post to help support the headers. The new header members (2x10's?) would sit on top of the built-up post with their ends interlaced together.

If the three dimension lumber header members are 4 1/2" wide and set to the outside face of the framing, the worst bearing of an individual header member would be 2 3/4" and the best would be 7 1/2". The shortest bearing could be at the less loaded header.

The visible face of 3/4" thick window casing trim in the corner would be about 1 1/2" each side and 2 1/4" at the back since of the trim since 3/4" is lost in the mitered corner.

Of course, there are other ways to do it but the only way to understand it is to draw the detail.


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RE: Any device to meet 2-jack stud req't with 1-jack?

I like the laced idea from Macv; I would go so far to say that if a heave steel corner angle through-bolted at the inside intersection were to be added to the system, no jacks would be required, just the new parallam post. Then your corner would be 6" square, and the windows would only be that far apart.
Of course, this is just a WAG.
Casey


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RE: Any device to meet 2-jack stud req't with 1-jack?

For the interior trim geometry to work there would probably have to be about a 3/4" space between the window frame and the post (normally 1/4" or 1/2") which would result in a 3/4" x 3/4" interior trim in the corner (unless you want to miter the window frames or their jamb extensions together).

That arrangement would probably work if an engineer specified two LVL's as headers (3 1/2" wide) and placed them at the outer face of the framing.

But I don't know the loads or the space above the window so please don't take any of this as more than design ideas. A design professional needs to look at all of the structural conditions and figure out what works. That may have already happened and there might be a structural detail ready to be submitted for a permit.


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RE: Any device to meet 2-jack stud req't with 1-jack?

Hi macv and Casey, thanks for the additional input on this.

I'm going to set up a meeting with the architect to ask for the details about what he was intending about the structural details. My expectation was that what I was contracting to get was whatever is needed to submit for the permit--and if that's not also his expectation, then I need to find that out now.

I won't take this as more than design ideas. From all you've written, I understand that the actual, live loads matter to determining the appropriate solution. I really appreciate the detail you've given because it will help me have a more informed conversation with the architect.

Thanks again!


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