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edward r 01-31-2009 09:00 AM

replace floor joist
my 150 year old farm house has bouncing kitchen floor syndrome. I removed the 3/4 flooring. my joists are 2' on ctr. Some rot not real bad. the floor is 16' X 16'. My friend wants to put 3 I beams under the kitchen. remove all old joists . put in all new 16" ctr. I know it would be good , but over kill !! I would put in 1 I beam in the ctr, rest the other ends on the existing foundation. double the existing floor joists. leavingthem on 2' ctrs. there are to many options. help thanks ed.

Scuba_Dave 01-31-2009 09:14 AM

If you have the floor up it makes sense to do it right
What size are the existing floor joists?
Depending upon the wood you need 2x10's for 24" spacing

My self I would be inclined to add joists so that they are all spaced at 12". 2x8's would then work at 12" spacing. You want to add an I-joist in the middle, perpendicular to the joist as support? That would effectively cut the span down to 8', so 2x8 or better would work. Something like this you only want to do once.

Termite 01-31-2009 09:48 AM

I like Scuba Dave's idea about adding joists in between the existing ones. What dimension are your existing joists?

I can say with a fairly high degree of certainty that your friend's idea of using three beams is overkill. One beam down the middle of the span would reduce the span of each joist to 8' and would result in an incredibly stiff floor. A good lumberyard (not a box store) can size an LVL beam for your application. You would need to place a couple pad footings for the LVL's support posts at each end, as I doubt that a home that old will have a spread footing that you could bear the posts on.

bjbatlanta 02-02-2009 06:11 PM

Agree, replace or sister the rotten ones and add the 12" centers as suggested. One beam.

SNC 02-03-2009 07:06 AM

Scuba has it pretty close. 2x10 spaning 16 feet is streaching it. then 2' oc not good enough.
The biggest problem with these old floors is the joist always seem to be to small. ( like 2x6 or 2x8 instead of 2x10)

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