How to stabilize a shaky floor

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Old 04-19-05, 09:58 AM
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How to stabilize a shaky floor

I have a 16 x 30' cabin on posts. The 2x10" floor beams span the 16' width. My floor is very unstable. When I walk, the stuff in the cabinets rattles and the floor bounces up and down. There is no room under the crawl space to put a supporting beam down the center. Will bridging work? How about adding another 2x10 beam next to the other joists? I would not be able to add the full length as I can't get new beams under the edges. Help! I want to add plumbing and need to get this fixed first. Thanks! I am in Minnesota, so any center beam added would need to be on posts dug at least 5 feet into the ground (below frost level) and this is not an option.
 
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Old 04-20-05, 02:44 AM
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hi
you will need 3 set of bridging space equal distance from the 2x10
ex: 16 ft / 4 = 4 ft.
mark from the egde 4 ft,8,12
draw a chalkline and place your bridging there
I would recommende cross bridging X

Good luck

pg
 
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Old 04-20-05, 03:11 AM
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Wink

16 ft should have been a 2x12. But like said put the 3 sets of bridging in . I like to cut blocks of 2X10 to fit in each joist spacebetter than the X set up for here.


ED
 
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Old 04-20-05, 03:58 AM
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Will floor hold weight of water heater and bathtub?

Thanks for the recommendation to use bridging every 4 feet. I plan to add plumbing. Will the bridging alone make the floor able to hold the weight of about 400 pounds of water heater with water (40 gallon electric water heater), plus a bathtub? Also, the refrigerator is on the other end of the cabin, opposite the water heater and tub. Like I said, I cannot put a beam under the cabin as the crawl space is too low to the ground. Thanks for your advice. I really appreciate it. (Would doubling the joists in that area be a solution? I cannot get new joists under the very ends as there is no way to access them.
 
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Old 04-21-05, 02:48 AM
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Boy ho boy
Not sure it this thing will hold.
why not jack up the cabin and then you will be able to brace it better from under.

good luck

pg
 
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Old 04-21-05, 08:01 AM
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In addition to the bridging you might consider also reinforcing the joists by adding a flange (say a 2x6 or 2x8) centered on the bottom of the existing joists to form a T section (upside down T). It can be less than full length (say the center 12') but it will require lots of nails to be effective (say 2" centers for 2' each end and 6" centers for the rest). Use a nail gun and the biggest gauge nails possible at least 3" long.
 
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Old 04-22-05, 03:12 AM
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I had a construction guy out. He recommended bridging and also sistering the joists with additional 2 x 10's under the bathroom and kitchen area (the first 10 feet of the cabin). They will do the job on Monday, weather permitting. Do you think this will take care of the situation? Thank you for your thoughts.
 
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Old 04-22-05, 10:38 AM
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If my calculations are correct......

The moment of inertia of two 2x10's sistered is 214.
The moment of inertia of a 2x10 flanged with a 2x6 is 267.
The moment of inertia of a 2x10 flanged with a 2x8 is 299.

This means you get more resistance to bending with less lumber if you flange your existing joists and make a T section, but the two have to be nailed securely (as I posted earlier) to resist horizontal shear at the joint to be effective . The two pieces have to act as one piece.
 
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Old 04-29-05, 03:30 AM
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Thanks for the very helpful info. One of my neighbors tried to raise his cabin to add a beam and it tipped on it's butt! I am glad I didn't go that route. They added the bridging to my cabin (three rows as you both suggested) and sistered the joints. All seems to be doing the job. I also adjusted the location of the water heater, so I think the set up will be acceptable. If things look shakey, I will have them add the flange.
 
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Old 05-01-05, 05:59 PM
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Steel reinforced

I wonder if it might be easier to screw on a piece of steel, or sandwich the steel with wood every other one. I've seen beams done like this before. I also read an article I think in the Journal of Light Construction several years ago of attaching steel strapping on the underside of floor joist to take the bounce out...
 
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Old 10-26-07, 09:58 PM
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Shaky floors in my mobile home

I live in a doublewide mobile home on a cement foundation. Over the last few years I have noticed that my floors throughout the house are shaky and when I walk on them, the kitchen cupboards rattle as well as my hutch. Do you have any suggestions on how I can repair or stabilize my subflooring??
 
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Old 10-26-07, 10:39 PM
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supports

if the spring is coming from a flex action in the floor, cut the span length in two by installing a support beam down the center from underneath. This could be done with a few 2X10's sandwitched and the edge centered at the midpoint across all the floor joists. Then support it from beneath with 4X4's, 3 feet on center, sitting on a 4X6 pressuretreated footer. In place of the 4X4's, you could use screw type adjustable lally columns, and snug them up as it sinks in the ground a bit each year, only if needed. It's either that or pouring a footing.
 
 

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