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Old 01-11-2009, 06:43 PM   #1
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Bouncy Floor/Sag

I just bought a house that is only framed in. There is no utilities in the house, no wiring, duct work, etc. It has been sitting for a long time like this. They used 1 x 10's for sheeting the roof, floor and walls just to give you an idea how old it is.

I have been working on the house and have noticed that the floors are bouncy and I am trying to figure out the best way to reinforce them. The is also a little bit of a sag in the middle of the joist span. The floor joist are 2x8 and the spans are about 13' where I am having the issue. There are metal cross braces put in I would say every 5 foot. There are no beams in the basement, just supporting block walls so the joist are all one piece spans. I was going to sister maybe every other joist but I doubt that I could get another 2 x 8 x 13 joist up there. I was thinking about using 2 x 6 instead. Those I should be able to finagle in there in one piece. How much would this help or am I wasting my time going this route? I hate to put any beams in because the ceilings are only maybe 7' tall. Any input would be appreciated. Thanks.


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Old 01-11-2009, 09:18 PM   #2
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1x10's? Exactly when was this house framed? Doing it with 1x10's is goofy.

Your 2x8's are not overspanned assuming they're spaced 16"oc. Adding additional 2x's to them will certainly increase their performance. Since you have nothing but framing I can't understand why you can't add 2x8's...They'd give you the most benefit. But 2x6's won't hurt either. The metal cross bracing is very beneficial to the floor system. You might also try adding solid wood blocking between the joists every few feet for added benefit.

I would also reconsider leaving the 1x10's as floor sheathing. That was great in the 1940's but isn't really a modern practice. 3/4" plywood or OSB is much more effective at "load sharing" loads from joist to joist, thereby reducing the floor's overall deflection.


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Old 01-12-2009, 06:48 AM   #3
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I would say the house is about 40 to 50 years old. The guy that owed it framed it in, roofed it and never finished. The floor, roof, exterior walls were already sheated with 1 x 10's. I am going to put underlayment over top of the floor. The floor joist are 16" center. I don't know why the floor is bouncy with that span. Since the joist sit wall to wall, i don't know if I would have enough room to put to get a 2 x 8 in there or not. I haven't tried but it looks like it may be tricky.
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Old 01-12-2009, 12:45 PM   #4
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are you planning on finishing the basement? If you cant sister in more 2X8's which is a good idea, you could put a header in the basement center of the span to support that floor. 2X8's might be good enough for code for floor joists but that span is pushing it and it wont get better in time.
A structural engineer could come by and recommend what size header or "I" beam would be best for you if you chose this route.
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