As part of a much larger building project, I will be replacing a 12 foot section of wall between two rooms, which includes removing two 2x4s and one 4×4. The 4×4 is due to the house being built using balloon framing. The wall used to be the exterior wall of the building; as such, it is definitely a load bearing wall, though it is only supporting the roof. There are no floors above.
My question is about support. Everywhere I've looked says that any passageway through a load-bearing wall must be supported by a cement lintel or similar; however, that seems like overkill, since the wall is only going to be holding up a portion of the roof and ceiling.
I am planning on using two sistered 2x10s, supported on each end by vertical 2x4s attached to the original vertical supports (4x4s, in this case). Will that be enough to support the arch and the ceiling/roof above? If not, would adding a third 2×10 help? If those options aren't enough, what other options do I have?
On the other hand, could I safely use less support – sistered 2x8s, or even 2x6s?
Best Answer
The cement lintel would be for brick walls, right?
To determine the size of the lumber you should use, you have to consider the load it will be carrying (the roof, snow, attic...) and the distance spanned - the whole 12' if I am reading your question right.
This picture
is from a site that has lookup tables to select the company's engineered lumber products but it illustrates the calculation well. Here is a lookup table provided by a county in Maryland:
http://www.aacounty.org/IP/Resources/HeaderSpanTable.pdf
It's a simple table that one would assume is based on standard structural engineering for the snowfall typical in that locale. (Which is not a lot of snow!) You can see that in that locale, even two 2x12's won't fly for a 12' span. You'd have to move up to engineered lumber or a box beam or etc.
So you're seeing spanning 12' is a whole different animal than putting in a doorway or window. To be safe, you could
1) hire an architect / structural engineer 2) hire a competent contractor and let them handle it 3) if the job has a permit, ask the inspector
(If you go routes 2 or 3 it might ultimately wind up back at 1 depending on your local regulations.)