Suggestions,
I have a basement remodel in an old house. The 1st floor is 2×8’s laid on side as a subfloor over 2×6 joists 24″ on center. The joists are 20′ long and are supported about mid span by a 4×4 beam that spans 14′. this does not seem enough although it’s been that way for decades. The owner is opposed to adding more colums to reduce the 14′ span and since there is only 6’5” of headroom now he doesn’t want a deeper beam. Would adding a 4” steel I-beam next to the 4×4 do much? Should I add more 2×6 joists to to bring the joist spacing to 12” on center? I’ve thought of cutting the floor joists next to the 4×4 beam, scabbing on a lvl or gluelam and using joist hangars to re-attach the joists but there is duct work in the bays. What would you do?
Phil D
Edited 2/7/2006 10:07 pm ET by TandM
Replies
The 4x4 is useless. The right way to do it would be to cut the joists and slide a beam in between them, then apply hangers. Within reason the ductwork can be redone.
happy?
Phil,
I can't remember the regulations exactly but if you assume a 40 lb/sf live load(People walking around) and a 10 lb/sf dead load(materials for floors). Then assume that your proposed beam will support half the load on either side of the beam this gives you 50 lb/sf times 10 lf to give you a distributed load of 500 lb/lf. Therefore the maximum moment would be 12,250 lb-ft
you should consult an engineer but a beam section in the range of W6x12 (6inches tall by 12 lbs per foot) or W8x13 should be adequate. This assumes you are only supporting the floor you described. If you have a second floor or the attic and/or roof loads bear on the floor you are describing forget everything I have said (that is why you hire an engineer).
Anyway definitely sink the beam up into the floor and use joist hangers.
Maybe one of these: http://www.betterheader.com
Apparently they will size the beam for you. A mid-range 6" tall beam oughta be very stiff.