Expert: Richard Taylor, AIA - 2/11/2004

Question
HI I have a question about a bearing wall. About 11 years
ago I put a 20 x 42 framed addition on my house. This is a
flat ceiling with the trusses running the direction of the 42
feet. I have 2 bearing walls supporting these trusses one is
about 10 feet in from the outside wall the other is 12 feet
in from the other outside wall. The wall in question is 12
feet from the outside wall. I am planning on putting a new
kitchen in this new addition and want to take out the
bearing wall and put a beam with or without a post. I am
just not sure how thick the beam should be. The bearing
wall is almost 20 feet long but I am leaving about  a 3 foot
wall on each end which will leave me with a 14-15 foot
opening for the beam. When setting the beam on the walls
how far into the 3 foot wall should the beam sit. Will a
2x10x16 feet doubled with plywood in the middle be long
and strong enough to hold the roof up if I dont use a post
to support the beam. I live in florida and the roof is a 4/12
pitch if this matters.Thanks Bob

Answer
Bob:

Thanks for your question!

I can't make a formal structural analysis in this forum, but I can give you an idea of where you stand.  Assuming I've understood your situation, two 2 x 10's won't be enough.  You'll need at least (3) 2 x 10s, and you might want to consider a couple of LVL's instead if you don't have the wall thickness for (3) 2 x 10s.

You should find a local architect or engineer to run the numbers for you if your building department requires drawings, but it sounds like (3) 2 x 10s should be enough for a 15' span.

Hope this helps!

Richard Taylor, AIA
Richard Taylor Architects, LLC
www.rtaylorarchitects.com