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Old 04-09-2008, 01:43 PM   #1
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Adding support to subfloor from crawlspace?

I just bought a house that has a small amount of movement in the kitchen by the fridge. It is nominal and only really noticeable if you do jumping-jacks by the fridge. I was wondering if there is a way to add some support to this area to alleviate the issue. I am looing to do it myself and not cost a whole lot. I have thought maybe 4x4 decking posts and concrete slab footing similar to what you use on oustide decking...


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Old 04-09-2008, 08:55 PM   #2
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Pouring a small conccrete collar around individual posts as you suggest may work short term, but they will be succeptable to sinking over time. A better way is to pour a continious footing, with some rebar in it, upon which to support the "legs". Another option, if pipes and wires do not prevent it, is to either double the existing floor joists by sistering, or install additional joists from sill to sill between the existing ones.


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Old 04-14-2008, 07:45 PM   #3
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I have the exact same problem in my addition! My joists are 4x6 beams that are 48" on center, so I am adding 2x8 joists (I may over-build with 2x10) in-between them, 16" on center, as well as pier footings like you were thinking. Underneath the crawlspace is a concrete pad, which used to be the outside patio, so I wont have to worry about them sinking.
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Old 04-14-2008, 10:59 PM   #4
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What you're feeling is probably deflection in the joists. When you do your jumping jacks you're loading one, maybe two joists more than the rest of the joists in the floor system.

You can't eliminate it, but you can sure minimize it by adding 2x10 blocking between the joists, which is what is called load sharing. Every several feet in each joist space, add a block of 2x10 and nail it in. You can offset the blocks an inch or two to facilitate nailing.

The blocks, when tight and nailed, will take the load of your footsteps and "load share" it to other joists.

It is really easy and it does work pretty well, without spending a lot of money unless your floor joists are just drastically over-spanned.
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