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I have a second floor bedroom that is 10' wide by 16' long. The floor is 3/8 to 3/4 then back to 3/8 lower, then 1/4 to the bedroom door. How can I even the floor? I can not raise the new floor very much as it will end up too high at the door going into the hallway. Can I cut the joists at the high point to level the floor? Can I do this to all of the joists?

I have been trying so many different things over the past 3 weeks and I'm very discouraged.

Somebody did tell me that I could use roofing singles to even the floor. How would I go about doing this?

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When you say it's 3/8 to 3/4 then 3/8 - do you mean that the underlying joists are uneven, or the subfloor is unlevel but the joists are fine, or that the floor surface height varies but the subfloor is level? As for roofing shingles, some people are idiots. Nuff said. –  The Evil Greebo Mar 22 '13 at 13:30
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@TheEvilGreebo I think the shingles were cedar shims. He was talking about shimming it up. Sounds really tough to me. –  Chris Cudmore Mar 22 '13 at 13:39
    
Ok that makes more sense but still a bad idea if you're doing anything other than shimming the joists resting on support posts. Shimming a sub-floor leads to uneven pressure distribution along the joists. You generally can't shim a final floor finish. –  The Evil Greebo Mar 22 '13 at 13:41
    
I'm no carpenter, but if the joists are uneven without any flooring, the difference does not sound that bad. All I know is to NOT cut the joists. I suppose it really matters on what type of flooring is going in. –  nportelli Mar 25 '13 at 13:42
    
How about some pictures of the problem? you've provided too little information. It could be simple or it could be a lot more work than we think. –  Matt Aug 11 '13 at 21:36

2 Answers 2

First, you need to find out WHY the floor is uneven. Are the joists sagging? Then you might have some structural issues.

From your description, it sounds like you have no boards over the joists right now. Is this correct?

I would not cut the joists, as this will cause structural weakening. You might be able to use a block-plane to shave down a particularly high point, but I wouldn't plane too much.

As for the shingles, I believe your friend was talking about wooden, usually cedar, shingles. These are tapered, and could be used to shim up a low spot, but I don't think it's very practical for a big job.

If the joists are the problem, there are three scenarios.

Joists are twisted, but longitudinally level.

This is the simplest. If you joists are 2x8, then buy a couple of 2x8's and cut them down to the appropriate spacing. Then bang them in between every pair of joists to straighten them up.

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Each Joist is level, but they have different heights

You could find the low ones and cut (rip) a thin piece off a 2x4 to attach to the tops of the low ones. It could be a bit tricky to get the thickness right.

Joists are bowed

I think the easiest option would be to sister the joists with new joists, only slight higher, so that the tops of the new joists are level and even over the entire floor.

However, you're probably not going to be able to tie the ends of the new joists into the structure. This means that they're going to have to be extremely well connected to the old joists. I'd recommend glue, and bolts with washers right through the mid-height line of both joists. (The center being the zero-force axis of a beam.) Drill the holes ever so slightly wider than the bolts, so that you can torque them nice and tight.

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If the joists are individually level but uneven from joist to joist, instead of a shim you should cut a strip of wood to the desired thickness and fix that to the top of the low joists, to avoid low points. –  The Evil Greebo Mar 22 '13 at 13:42
    
@TheEvilGreebo Good point. I was thinking in the other direction. As well, they could simply be a bit twisted, and stabilizing blocks might help. –  Chris Cudmore Mar 22 '13 at 13:43
    
Agreed, in that scenario shims are fine. –  The Evil Greebo Mar 22 '13 at 14:21
    
yeah but im 3 inches low at the door level can i sister the joists with glue and bolts and cut the original joist 3 inches to bring down the high end to level at the door going out to the hallwill i have support on the low end with a wall from underneath but the other end will not be just bolted to the joists can i do this –  allan gauthier Apr 6 '13 at 1:19
    
I think you need professional advice here. It sound's like you might need to jack up the house. –  Chris Cudmore Apr 8 '13 at 15:17

I am presently renovating a house that has a 4" differance from one side to the other due to old settling not ongoing subsidance so your problem is my problem,how to level the floors ,ceilings etc.

FIRST:- You must find out WHY the floor level has changed,what has caused it? Get expert advice,not some guess work, before you do anything.

Second:- do not start cutting the joists you will weaken them and could end up with them failing..= worse problem.

Assuming you have the floor up and are looking at the joists I would find the highest joist and draw a level line around the wall at this point. starting from near the middle of the room add sister joists, as the other post details, and work out to the edges.

Don't forget that your ground floor ceiling is probabley attached to the lower side of the existing joists, so if you try and move the original joist positions you will end up destroying the ceiling below... not cheap...

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