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Sustainusfarm
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# Posted: 6 May 2012 10:05
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Good Morning all, I built my cabin 10 years ago, still working on it though  . When I built the floor system I used 2x8 joists...it seems that the floors are a bit bouncey and everytime we walk form one end to the other the fridge rocks back and forth, the tv shakes and if your sittin' down on a chair and someone walks by you really feel it! the 2x8's span 12 ft and there is 1/2" ply over that...any ideas how to fix this? Is it that I just need to get the finished flooring down to stiffen it up or should I put a layer of 5/8-3/4" T&G down first to stiffen it up? I cannot get under the cabin to do anything from the underside, to close to the ground. Any ideas would be most helpful...
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toyota_mdt_tech
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# Posted: 6 May 2012 10:41
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Well, 2X8 going 12 feet is fine, I assume you went 16" OC. I would of used atleast 3/4 or 1" tongue and groove for the flooring. 1/2" is just too thin. You could install "X" members between joist, this will really tighten it up. Cant you just lay another row if floor sheeting opposite direction? I assume you staggered your sheeting joints.
OK, seen you cant get underneath, so looks like heavier sheeting is the only option.
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Sustainusfarm
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# Posted: 6 May 2012 10:48
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TMT, thanks for the response...Yes they are 16" OC and the sheeting joints are staggered...do you think I should put a layer of felt paper down before I put down the next layer of ply?
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Anonymous
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# Posted: 6 May 2012 15:48
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Has it always moved that much? Can you be sure that the subfloor/foundations haven't moved?? Using a 1" T&G flooring will do a good job of spreading the weight and will remove some of the movement, but if the foundations aren't solid it will just put more weight on the existing piles which might already be moving.
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Sustainusfarm
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# Posted: 6 May 2012 17:55
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it is not the foundation...it has always been springy and when I first built it I thought that that was the way it is supposed to be until finish flooring got put in..I put 5/8" T&G in an addition and it is not springy at all...rock solid. Also I put tile in a sunroom area and put down 1/2" cement board ontop of the 1/2" subfloor ply and now it is super rock solid too...apparently the fix will be another layer of T&G to stiffen it up. Thanks
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sparky1
Member
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# Posted: 6 May 2012 21:53
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My 2 cents;
If your going to add another layer, Change the direction of the new flooring for Better strength,
sparky1
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dk1393
Member
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# Posted: 7 May 2012 07:52
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My cabin is 16x20. It has 2x8 joists and half inch plywood floor down. It was also very spongy. I put 3/4" tounge and groove flooring down. It made an amazing difference. No more spongy floor
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TomChum
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# Posted: 7 May 2012 10:25
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Depending on what you have below the cabin, could you cut a hole in the center and drop a pierblock on the ground? Put a 4X6 across the 2,3,4 center joists, whatever you feel like. Gravel, sand, concrete, you can got pretty complicated but i suspect just a simple pierblock in gravel would solve your problem in a couple hours.
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MtnDon
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# Posted: 7 May 2012 14:22
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FYI. 2x8, average species used for construction, spanning 12 feet, 16" OC is marginal. It is at the upper limit for #2 Hem-Fir, S-P-F and Souhern Pine is not much better. 2x8's are pushing it. Remember tables and online calculators list maximum spans; if you're near the maximum things can get bouncy.
!/2" subfloor is too thin. Again, the code books, etc. list minimum thicknesses for subfloor. 5/8 OSB or Plywood is minimum for 16" OC by code, and there is good reason for it. Combine joists and subfloor and you have a trampoline.
I'm the cautious sort. If it was me I'd nail down minimum thickness 3/4" T&G OSB (or plywood if you prefer) over the entire existing subfloor; If you can get 1 1/8" OSB like I can I'd opt for one of those. Install it the right direction, 8 foot dimension perpendicular to the joists, but stagger them so none of the seams overlap in the two layers. Then install whatever finish flooring suits you. I'd go in the direction of more is better than less because then there is more of a chance you will be happy with the result. It's hard to make up for springy joists.
OR
Cut out enough of the existing floor down the center so you can install a center beam with some good footings at each end and down the middle. Then I'd still do 3/4 subfloor.
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Speedgeeza
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# Posted: 9 Jun 2012 13:25
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Yeah, MtnDon has hit the nail on the head. Max span for 2x8 spruce for example, is 12'3''. Sounds like the proper fix is to drop some extra support piers before the new floor goes down if you're going to eliminate the problem completely.
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toyota_mdt_tech
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# Posted: 9 Jun 2012 14:29 - Edited by: toyota_mdt_tech
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My cabin plans are engineered and my 2X8 floor joist spans are 12 feet long at 16" OC. Flooring is 3/4" tongue and groove and its all rock solid. Absolutely no bounce. I'd say his joist and spacing is OK, its his floor sheeting, its too thin. My sheeting was laid apposite direction of joist, staggered like bricks. Glued and nailed.
My plans were inspected by the county and OK'd before work started.
I think if he lays down 3/4" T&G sheeting opposite direction of his 1/2" sheeting, it will become rock solid. .
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Sustainusfarm
Member
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# Posted: 9 Jun 2012 23:24
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Ok... Done!! Not a bounce in it!! In fact, I cannot even feel someone walking past my comfy chair!! I think I am in for some sneak attachs now while dozing!! Ha... Thanks all!! This has been a 10 year irritation.. Now I should probably drywall after 10 yrs!!??
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