Uneven Sub Floor


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Old 02-23-11, 08:58 AM
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Uneven Sub Floor

I want to install hardwood but the sub floor is uneven (1/4" over 8'). I had the floor joists checked and have been told that structurally they are fine but the joists in the problem area are different heights and hence the 1/4' drop in the floor. I was told that the offending joist(s) can be shaved to create a level surface. Is this OK?
 
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Old 02-23-11, 03:23 PM
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Welcome to the forums!

..... so you've removed the sub floor? It should be ok to shave the high joist providing your joists aren't undersized to start with.
 
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Old 02-23-11, 04:20 PM
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No, I haven't removed the sub floor yet. Still in the planning stages. I would hope to only have to remove the section of sub floor to expose the high joist and then replace that section. I don't think the joists are undersized but what is the standard size. The house is approx 40 years old.
 
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Old 02-24-11, 05:31 AM
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Generally floor joist sizes start with 2x8s but it depends on the load and span. Longer spans require bigger joists.
 
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Old 02-24-11, 12:47 PM
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The joists are 2x8. If I shave a 1/4" off the joist that is slightly over 8" will I compromise the structure? I assume I'll need to expose the joists either side to know when I'm level.
 
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Old 02-26-11, 09:50 AM
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You said you have a 1/4" drop in the floor. You also indicated that one joist is high which would create a hump, not a dip. This is important because a dip can be addressed by shimming up the low joist, which is relatively easy. If you have a hump, I don't think planing it down 1/4" will cause much of a problem. To be safe though, I would sister 8" strips of plywood on both sides of the joist along the planed area, attaching them with good quality construction adhesive and 1/2" bolts, nuts, and washers top and bottom every two feet. Try to extend the plywood several feet past the planed area if you can't extend the to vertical support.
 
 

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