Header span

[bmancanfly]

I'm opening a wall between two rooms. The neW opening will be 12' 8". I have a header span table and it indicates that the maximum span for a 4" X

12" header is 12'. The header is only going to support the 10' long ceiling joists above (no roof or floor above). If I increase the header to a 6" X 12" will this work for a 12' 8" span? Or will I need an LVL. IF SO WHAT SHOULD THE DIMENSIONS OF THE LVL BE? Thanks in advance

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[SteveBell]

Check your header span tables for the maximum span for a 4x12 header.

[bmancanfly]

bmancanfly had written this in response to

:

------------------------------------- SteveBell wrote:

I guess what I'm asking is how do I span a 12' 8" opening?

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[SteveBell]

If I were doin' it, I would:

• Build a temporary wall to support the ceiling. You'll probably need one for each side.

• Demolish the existing wall, leaving the top plate in place.

• Build a typical header support at each side of the opening--two jack studs and a king stud nailed together.

• Build a beam out of two 158" long 2" by 12"[1] boards with 1/2" OSB in between to make it 3.5" wide. Make sure the crown is up on both boards.

• Get two buddies, maybe three, to help me hoist this monster up to the top of my header supports, then nail it in place.

• Install the cripple studs between the top of the header and the top plate.

• Remove the temporary walls.

• Install wallboard, trim, tape, bed, texture, and paint.

[1] Don't rely on me for the proper dimension. Consult an architect or engineer. [2] Your local code may require something different. Check first.

[Red Green]

brettgiardiello_at_bellsouth_dot [e-mail] (bmancanfly) wrote in news:49e75fb2$0$5376$ [e-mail]:

I know very little about spans but I did have some dealings with truss repairing. In that venture I did learn that different types of wood, say SYP vs spruce vs douglas fir have different strengths like tensile, tension, etc. It may be possible to simply use a different lumber than what's available at the Borg. Check your table for what the spec was for lumber.

[RicodJour]

People post such questions and often believe they are providing sufficient information. They rarely are. You've addressed dimensions, but not loads, and that is critical to answer any structural question.

You have a ceiling, which makes the space above an attic. Is that attic space now used for storage? Will it be? Did the original builders, or later remuddlers, decide to piggyback some of the roof load onto that interior wall? How do you plan to deal with the increased point loads at either end of the new beam? You mentioned 10' ceiling joists - is that 10' on each side or 10' total?

For an accessible attic space, whether you use it for storage or not, you should allow some load in your calculations - say 20 pounds per square foot. That's the Live Load, and it's not much as one box of books easily exceeds 20 PSF.

The Dead Load, or weight of the structure itself, is generally in the

10 to 15 PSF range.

If somebody did piggyback some of the roof load onto the interior wall (you'll see near-to-vertical framing between the roof and the interior wall location below), then you will have to add some of the roof loads (Snow, Wind, Dead Loads) to your calculation.

The Total Load is the sum of the the Live, Dead and Roof Loads.

The contributory area is the area that will add load to your new beam. Generally that is half of the span on each side. If your house is 20' wide, the beam in the middle will pick up half of the load on each floor joist from each side, multiplied by the length of the beam.

The last piece of information you will need is the desired stiffness of the new beam. If you have plaster ceilings you will need a stiffer beam to minimize cracking due to beam deflection. Generally 1/360 is a good compromise and that reflects a deflection of about .42" over your 12' 8" span (many people would choose a stiffer beam with less deflection).

You now have enough information to contact your local lumberyard/LVL purveyor and ask them to size the beam for you. This is a free service. They will plug in your numbers and their proprietary software will crunch the numbers for your specific situation and their specific products.

Ask them specifically what the beam end reactions are and how many supporting 2x4s you will need to carry the beam at each end. You will need at least two.

If you go with LVLs you will probably need, at a minimum, two 1.75" x

9.25". Remember that a beam gets far stiffer with increases in height (depth) - changes in width have relatively less impact on stiffness. R

[bmancanfly]

bmancanfly had written this in response to

:

Thanks for the reply Rico

I was planning on getting a 3.5" X 12" LVL. Since a dimensional beam could handle a 12' span I figured an LVL of the same dimensions could easily handle 12' 8" .

I tried gett> >>

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