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jtpwils 11-13-2008 01:15 PM

Header in a "modern brace" framed house
 
I'm planning an addition to my "modern brace" framed house. Modern braced framing is basically a cross between balloon and platform framing where the studs and joists at the foundation are the same as balloon but instead of the studs going to the roof, they go to a 4x4 top plate and the 2nd story studs rest on the same top plate, as do the floor joists for the second story.
I want to remove the wall that runs parallel to the 2nd story floor joists and have the header hidden. My question is this:
Can I locate the header on the exterior side of the existing 2nd story studs and hang them off of the header or do I have to trim them and locate the header underneath them?
Let me know if I need to post a sketch.
Thanks,
Jim

Wildie 11-13-2008 06:21 PM

Quote:

Originally Posted by jtpwils (Post 184356)
I'm planning an addition to my "modern brace" framed house. Modern braced framing is basically a cross between balloon and platform framing where the studs and joists at the foundation are the same as balloon but instead of the studs going to the roof, they go to a 4x4 top plate and the 2nd story studs rest on the same top plate, as do the floor joists for the second story.
I want to remove the wall that runs parallel to the 2nd story floor joists and have the header hidden. My question is this:
Can I locate the header on the exterior side of the existing 2nd story studs and hang them off of the header or do I have to trim them and locate the header underneath them?
Let me know if I need to post a sketch.
Thanks,
Jim

You never said what the span is of the wall that you want remove.
So, everything on the second floor must be supported. This is the 2nd story wall, perhaps the ceiling and the roof structure.
I would guess that a beam of at least 12" wide would have to be placed under the 2nd story studs.
To do this, these studs would have to be shortened enough to allow the beam to be placed directly underneath.
This alone would be a tricky operation, as the weight of the structure above would have to be temperarily supported until the beam is in place.
I would suggest that an engineer would be consulted for this problem.

Maintenance 6 11-14-2008 06:32 AM

You have to trim the studs and install a header underneath them. Otherwise those studs would not be bearing on anything and will eventually sag. You can set the bottom of the header flush with the bottoms of the joists on either side of the wall provided that the span is matched to the size of the header and the load that it must bear. You need cripples under the ends of the new header to carry the load to the sill.

Marvin Gardens 11-14-2008 09:22 AM

Pictures would be nice.

jtpwils 11-17-2008 03:18 PM

1 Attachment(s)
Thanks for your replies. I probably wasn't clear if it seemed that I didn't realize that the studs and the header need support. I am an engineer, and I built my own addition in my last house but that was platform framed; which made things a lot more straight forward.

The attached simplified sketch gives a better view of my problem. The 2nd floor studs support the roof, and 1/2 the attic span but not the 2nd floor. The problem that I have with trimming the studs is that it means I mess up the existing 2nd floor floor because the beam is taller than the joists.

Thus I want to hang the 2nd floor studs on the side of the beam using joist hangers. The reason I'm not sure this is allowable is because there will be a fairly considerable torque trying to rotate the beam CCW.

The span of the new header is 13 1/2 feet. The beam show is calculated with a Parallam PSL 2.0E beam with 1/2 the exsting roof and attic spans, 1/2 the new roof span, 1/2 the new 2nd floor and the 2nd floor live and dead loads using L/360 total load, L/240 live load, as well as allowable shear and moment for the beam.

Wildie 11-17-2008 04:11 PM

From what I see, rotation of the beam in a CCM would be countered by the weight of the new joists!
The new joists support what? A roof or a floor?
What will support the new beam?

buletbob 11-17-2008 04:39 PM

Whats that new 5' of rafter span going to be? doe it require a roof? what I'm thinking is if there is a shed type roof design, I would have the new rafters with a slight birds mouth cut into it and spiked along side the existing studs also with your design. I see why you don,t want to loose the security of the floor to wall. BOB

jtpwils 11-17-2008 04:40 PM

Quote:

The new joists support what? A roof or a floor?
In the middle of the span the new joists are for a platform bed so not much load there. Otherwise the rafters are doing their "normal" job of stopping the exterior wall from pushing out due to the smaller roof over the addition area. The other half of the addition roof load will go back to a ledger that is on the existing 2nd floor wall studs.

Quote:

What will support the new beam?
The house is like a "T" The header is replacing the "up and down part" thus one end of the header will be supported by a column in the middle of the existing wall. On the other end, which is now a corner, the beam will rest on the top plate of the new section, which I am going to extend into the existing wall. Directly under the new header I'm placing a window so that it's header spreads the load to the old and new foundations and not at the joint between the two.

I knew I should have drawn more.

jtpwils 11-17-2008 04:47 PM

Bob
I'm not sure I follow you. Are you suggesting the roof rafters tie back directly to the 2nd floor studs and not to a ledger board that is tied to the studs?
Your comment gave me another idea. I could tie (block between) the exisiting 2nd floor studs/header and the next adjacent interior floor joist and use a dbl width hanger.

buletbob 11-17-2008 05:24 PM

correct! open the wall and tie the new rafters into the existing studs the beam will act as a support for the roof and the rafter nailed to the stud will keep everything tight. BOB

jtpwils 11-17-2008 05:45 PM

Ok thanks. I'll also interpret your answer as an implicit "that's legal" as far as the studs to header connection. Naturally, everything will go through the local permit process but I want to submit a plan that's right to begin with.

Termite 11-17-2008 06:16 PM

That is an incredibly unconventional design, with the studs bearing to the beam in joist hangers. The first thing I see wrong is that there is no way for the studs' loads to transfer to the foundation (via the beam) with the required 4" nominal. The <2" saddle of the hanger is inadequate. Furthermore, the joist hangers themselves must be capable of taking the imposed loads from the roof and the tributary load from the floor, as well as wind load that the wall resists....I'm skeptical.

If you're an engineer, why are you asking this question on a DIY site? (I know, there are all sorts of engineers, and structure might not be your thing). I can tell you that as an inspector, a design like that would not get approved by me without a structural engineer's stamp on it...It is just too unconventional.

Wildie 11-17-2008 07:50 PM

Quote:

Originally Posted by thekctermite (Post 186510)
That is an incredibly unconventional design, with the studs bearing to the beam in joist hangers. The first thing I see wrong is that there is no way for the studs' loads to transfer to the foundation (via the beam) with the required 4" nominal. The <2" saddle of the hanger is inadequate. Furthermore, the joist hangers themselves must be capable of taking the imposed loads from the roof and the tributary load from the floor, as well as wind load that the wall resists....I'm skeptical.

If you're an engineer, why are you asking this question on a DIY site? (I know, there are all sorts of engineers, and structure might not be your thing). I can tell you that as an inspector, a design like that would not get approved by me without a structural engineer's stamp on it...It is just too unconventional.

Just in passing, I'm wondering if having the studs bolted to the beam with carriage bolts would be acceptabe vs. joist hangers!
I expect that this would have to have an engineers stamp as well!

buletbob 11-18-2008 06:28 AM

JTPWILS: I do strongly agree with thekctermite about it being an unconventional way to frame. But your the Engineer. That's why I was trying to solve the problem that was stated earlier from keeping the beam from rolling. the idea of running the rafters on top of the header and nailed to the studs was to help to keep the header from rolling and locking it together,
The way I have installed this type of header was to lag screw a ledger board to the exterior wall above where the header is going to be installed. You will have to remove the siding from the wall to do this, plus it needs to be removed for the roof flashing anyway. once the ledger is installed, Install a 2x4 on the floor and run some 2x4's tight under the ledger,making them a little longer and banging them in. then cut out your studs to the height of the new header. remove the nails coming from the sub floor nail er going into the wall studs. you could pry the cut studs away and hammer the nails through and then pull them out of the nailer. install the header and your jacks & posts. then nail the trimmed studs to the header leaving it sticking out on the exterior side and flush on the inside. measure what you have from the second floor joist to the top of the sub floor and nail the exterior floor nailer top at that dimension,. this would be the only true conventional way to install this header. Sorrey for the miss understanding. BOB

jtpwils 11-18-2008 08:24 AM

Thanks again fellas. Yes, I'm a mechanical engineer in my day job but not a structural engineer. I realize it's not conventional, which is why I was asking here. I was hoping that some of you with experience in the field could say "I did that once". The hangers are rated for the individual loads to be carried in each stud, although I was unaware that I need to support the entire width. I'm sure there is another hanger that fits that requirement but it would still be an unconventional design.

In any event, I guess the best course of action is to contact a structural engineer if I'll need a stamp anyway. If he says I can't do it that way, then I'll trim the studs and put it in conventionally. In which case, thanks for your ideas Bob. Holding up the wall the way you suggest is in my plan, but I was figuring on using the same ledger that would be where the new roof rafters would be tied and not tying them to the studs directly.

I'll finish the section and submit it for review to an engineer. I'll report his finding back here.

Thanks again.
Jim


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