span and header size


  #1  
Old 02-11-05, 07:06 AM
kphillips
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span and header size

I am removing the top part of the wall between my kitchen and living room to create a half wall upon which I will put a countertop for a breakfast bar. The joists in the attic meet at the top of this wall. The wall supports the joints and the attic floor only and the load from this wall does not extend down to the basement. The roof is gable so the outside walls support the roof. The span will be about 12 feet. Given the span and the load I described, what size header do I need? I don't want to go bigger than 2x8 because of head room. I prefer to use 2x6's if possible, even if I have to put a column that sits on top of the breakfast bar counter and extends the beam (will that work).
 
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Old 02-11-05, 01:00 PM
S
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Is the attic used as living space or just storage?

With the understanding that there are floor joists of some sort underneath this wall. What is their size and spacing? Do they run the same direction as, or perpendicular to the wall? How far is this wall from the main beam?
 
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Old 02-11-05, 04:25 PM
kphillips
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The attic is just for storage but we hardly have anything up there. The floor joists underneath the wall are 2 x 10's and are spaced 16" o/c. The run perpendicular to the wall. The wall is about 3 feet from main beam.
 
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Old 02-11-05, 10:12 PM
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Originally Posted by kphillips
The floor joists underneath the wall are 2 x 10's and are spaced 16" o/c. The run perpendicular to the wall. The wall is about 3 feet from main beam.
I saw this and should have question it, sorry. You said that the ceiling joists "meet" over this wall. This means, that if your wall framing is 2x4, the "bearing" is 1.75", and since "full bearing" is considered to be 2.5", there should be at least a 24" "strap" of the same material as the ceiling joists nailed to them at that joint with 10-16D.

The correct framing that naturally maintains the structural integrity is to "lap" this connection, where it occurs.

However, going forward with the assumption that this wall is in fact a bearing wall, A thumbnail rule for sizing headers in "single story" residential is="1" of header depth, for every 1' of distance carried. and you round up.

For full span, that would mean the equivalent of a 4x12.

Headers longer than 8' are required to have either double "trimmers"/ "jack studs"(depending on your geographical location) or a 4x post on each end.

Were I you, I would develop two dimensioned drawings on 8.5x11" paper based upon one of the following designs.
1) Supporting the ceilings on both sides of this wall approx. 24" away, remove sufficient wall to accomplish the required framing, (using an existing stud as a "king stud") including the double top plates. Construct a header using two 2x12's with 1/2" plywood glued, sandwiched and nailed between them. After installing the header, renailing the ceiling joists you'll need to provide a "mechanical connection between the header and the top plates. (There are several methods depending if this header occurs in the middle of a long wall, is pocketed into perpendicular wall/s on one or both ends.) BEFORE removing the ceiling supports, install triple floor joists directly beneath the header support framing, on both ends.
(With an existing 8' ceiling height, this will result in a 7'+ header, leaving the double top plates, you'll have an 80"+ ceiling height.

2) Assuming installing an intermediate support post, leaving the double top plates and assuming that the "doorway" is 36" wide. The unsupported length is reduced to 9', so the required header would be equal to a 4x10 or equivalent. If the intermediate support is "turned" it needs to be a 6x6.
None of the support structure changes, however some of the mechanical connecter can be reduced and/or eliminated.

Submit these to a structural engineer. The cost will be minimal.
 
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Old 02-12-05, 11:49 AM
kphillips
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Thanks for your help. After thinking about it, it would be easier to go with the support in the middle (or almost the middle). The existing opening is actuallly almost 4.5 feet and we are going to reduce the span of the other side to 6 feet which is plenty to accommodate at least three bar stools.

.
 
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Old 02-12-05, 12:09 PM
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Originally Posted by kphillips
Thanks for your help. After thinking about it, it would be easier to go with the support in the middle (or almost the middle). The existing opening is actuallly almost 4.5 feet and we are going to reduce the span of the other side to 6 feet which is plenty to accommodate at least three bar stools.
Any time.

Again, were I you, I would at least install double, or double existing floor joist under the three support points, and keep in mind, that a turned 4x4 has no structural value.
Make sure that your intermediate support is full length.
 
 

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