Expert: Bruce E. Johnson - 10/4/2009

Question
QUESTION: Hi Bruce,
I am preparing to remove a load bearing wall and put up a header to open up the living room to the dining room. The R.O. is approx. 12'(+/-), one end of the header will abut the exterior wall(perpendicular) and the other end will be attached to an existing wall(end to end). This is a 1 floor home with an attic that was converted to living space above(on 2nd floor) and there is a dirt crawlspace with a concrete foundation perimeter, I'm not sure if the floor joist spacing is 16" or 24" O.C. and the original wall runs perpendicular to the floor joists The header will be a double 2 x 12 with 1/2" plywood spacers every 12" and the supports will be 4 ea. 2 x 4's boxed(rectangle) so that each end of the header is supported by 6 1/2". My question is, will that 6 1/2" bottom end of the support (that will now be supporting the header and all weight above) cause the floor below them to start to sag or bow over time because all the weight that used to be on the original sole plate running across several floor joists is now concentrated on one spot(6 1/2" x 3 1/2")at each end ? Thank you Bruce.

ANSWER: Hi Harry, Yes.  You are concentrating the load from that twelve foot section of wall to the two points at each end of the header.  If these points correspond with floor joists below then you can shore up the floor joists with a 4x4 post down to a 2'x 2'x 8" thick concrete pad in your crawl space.  If the beam end shoring is sitting only on the first floor decking then you need to run your 4x4 support up to the underside of the decking. This way you can be certain that your new concentrated load is properly supported.  As far as your header goes, I would make the 1/2" plywood solld instead of just strips between your 2x12s and I would also use some liquid nail glue in between all the pieces to glue the whole assembly together along with your nailing. I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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QUESTION:  Hello again Bruce,
I'm getting ready to start this wall removal job but I am unsure how big of a temporary beam to put above the temporary jacks, I was thinking a 4x4 at first, however since the bearing wall will be removed for 12'(+/-) and the jacks will be spaced approx. 7' - 8' apart I am doubting my first choice and think the beam should be at least a 4x6,or should I go bigger, any help on this matter would be greatly appreciated.I also have decided to go with engineered lumber instead of 2x (for the header) due to the fact that it is 1 3/4" thick and will need no spacer plate between the two boards. By the way, I want to support the ceiling joists on each side of the wall being removed at a distance of 2' - 3' away from the wall being removed to give myself adequate room to work,is this OK or do I need them closer? Thanks again in advance.

Answer
Hi again Harry, you can build a simple temporary stud wall with studs spaced to match your floor joists underneath or you can use a header beam.  A 4x6 will suffice with supports up to six feet apart but you may need to put your supports on a plate that spans over a couple of floor joists to split up some of the concentrated load.  Although unlikely, you may punch through floor sheathing if your temporary support posts are not directly over a joist.  Supporting your ceiling joists and rafters 2-3 feet away will work to allow you room to do the transition.  Before starting the demolition and beam replacement make sure you have all your materials ready to go so that you can complete the support work as quickly and as efficiently as possible. I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com