Expert: Nazim Nice - 12/7/2010

Question
In my house, I have four a kitchen and family room in the back of the house that are one large room.  The front of the house has a dining room adjacent to the kitchen and living room adjacent to the family room which is separated by a load-bearing wall.  It is a two story home with siding and a fairly low pitched roof.  The floor joists are 2X8 and the roof supports are 2x4's.  The area above the wall we want to remove and add a beam to contains 3  bedrooms and no bathrooms.  The span of the support wall is about 12 ft with the joists running perpendicularly from the front of the house to the back.  The house is on a concrete slab.  What I would like to find out is what type of beam I should use and is it possible to open the entire span or would I need a support post(s) in the center?  What is the most cost effective way of achieving this?  About how much should I be looking to spend on the beam itself?

Answer
Hi Nick,

If the opening is 12' then my guess is that you could span this without a post in the center. However you will need to have the beam, post, and footings sized by a structural engineer. It may be challenging to get a beam to fit within the 2x8 floor system (if you don't want to see the beam). If you don't mind seeing the beam, then it could likely go under the ceiling joists.  The structural engineer will also have to analyze the load at the ends of the beams and determine whether the foundation can support these loads. If one side is an outside wall, then it might be okay since there will likely be a foundation there. Your contractor may need to verify the size of the foundation to see if it is large enough (based on the minimum size the engineer determines is acceptable). If a point load falls where this no foundation, then the floor will need to be removed in that area, the concrete cut out, and a new footing poured (sized by a structural engineer).  Of course between the footings and the beam would be new posts sized by the engineer and he will also specify a bunch of steel connectors to hold everything together. The cost of the beam would vary depending on what the structural engineer calls out and whether or not you want it to fit in the ceiling so it doesn't show. If it is steel it will be more expensive, if it is wood it may be less. My guess is he may use a beam called an LVL. There is some pricing on this page that will give you an idea per foot what one costs:
http://www.dunnlumber.com/webtrack/products-catalog.php

My guess is that you would be looking at a larger beam like ones down at the bottom of that page (of course your engineer will determine exactly what you need). Sometimes engineers will bolt two or three smaller beams together as well.

Hope this helps!

Nazim Nice
Principal / Architect
http://www.motion-space.com
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