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Unread 11-10-2003, 11:44 AM   #1
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Location: Roanoke, VA
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getting subfloor installed level

Thanks to all the good advice I'm ready to install my kitchen subfloor (3/4" sturdifloor). I want to get it all nice and level before the CBU and then tile. My plan is to glue and deck screw the sturdifloor to the joists. Also, since I had to cut out the old subfloor leaving it sticking out around the edges I've used 2x4 blocking between the joists and then 2 pieces of 2x4 in an upside down "L" shape parallel to the joists. The 2x4's are nailed in place and glued and screwed to the edge of the existing subfloor.

Thanks to a week off work and my Dad doing the same to help out we accomplished enough to film a month's worth of "This Old House". Termite damaged lumber has all been removed and the originally poorly supported load bearing walls have been supported properly.

However the result is a mix of old and new joists in the kitchen which do not have a level or flat plane for subfloor install. The joists are level at the ends, but the new joists are higher than some of the old ones in mid span (some about 3/8 lower). Some of the old ones match up fine. Also some of the 2x10's in the girder stick up higher than the others which will make a bump across the floor.

Two questions:
1. Am I on the right track in the first paragraph of this post?
2. How do I bring up the low spots in the old joists that are low and lower the pieces of the girder that are too high? How close to flat and level do I need to be to do this right? After all the effort I've put in up to now I want to get this right so I don't feel like I'm walking around the carnival fun house.

Thanks for all your input up to now. Your answers here will make my wife and I very happy as we will be able to finally have a floor in the kitchen again and be much closer to being able to cook and eat normally again!
DIY'er always looking to learn something new!
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Unread 11-10-2003, 12:04 PM   #2
Sonnie Layne
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sounds all right, except I wouldn't have used the 'L' thingy, just two 2x's one under the old and one under the new would be fine.

The ideal situation for flattening out a plane is to bring all the low stuff up to the high point. Don't know how much overall you've got to deal with. You'd either have to sister 2x4's onto everthing to make up for the rise in the girder.

Why the upward bow? is there a pier there? We run into more problems with sag developing than the other way around. Unless.... uhh, you don't live in Australia do you?

I'd hate to say you could notch the girder.....
da' poet
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Unread 11-10-2003, 02:47 PM   #3
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Thanks for the input. Let me try to be more specific about my leveling problem.

BTW I agree on the "L thingy". I think I'm going to redo that. Looking back the original suggestion I got here on the forum was to sister some 2x4's to the rim joist (it will take 3) and attach them with some glue and lag screws. Should be much more rigid. On the box joist ends the 2x4 blocking is fine as it can nail between the joists in the right spot.

The joist level problem across the joists is really just 2 old joists that are low through a stretch in appox 1/3 the span on the end toward the foundation wall (not the girder). I think the problem is mainly that we're dealing with 80 year old lumber vs. stuff I just bought. The difference is 3/8" at the very worst (I think it's less, but I'm not there right now). Can I glue a plywood shim to the top of the joist to even things out? BTW the joist span in this section is about 13'6".

On the girder the problem is in the construction of the girder and possible movement between the pieces over 80 years. The girder is 5 2x10s nailed together in this part and the tops are not all exactly even. The worst is probably 1/4" high. Unfortunately the joists are level when their tops are even with the lower pieces. I completely understand what you're saying when you shy away from notching the girder, but do you think planing 1/4" off the top would be OK? BTW the girder span here is about 9'.

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Unread 11-10-2003, 06:25 PM   #4
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I do old homes, and I wouldn't care what it looked like if I was doing your job.

I would slap the plywood down as best as I could, and leave it.

Then, I'd float a mud bed. I have tried and tried to level old floors using sistered joists-using shims under the ply-using shims under the CBU. I've never been able to find a technique that actually levels the area without a huge mess and drill.

Quite frankly, it is easier and cheaper to just float a mud bed for a crooked floor.
"Sir, I May Be Drunk, But You're Crazy, and I'll Be Sober Tomorrow"
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Unread 11-10-2003, 06:41 PM   #5
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I agree with Scooter about the mud, that's how I'd do it too. It's just hard for a DIYer to mud a floor nice and flat without any experience but it can be done.
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Unread 11-10-2003, 09:06 PM   #6
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For the two or three joists that are lower than the others, sister these with some 2x6s with the tops of the sisters level with the others.

This is better than shaving all the high joists.
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Unread 11-10-2003, 10:44 PM   #7
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I gotta agree with Bob. Unless, of course, you decide to do a mud bed.

I think you're fine with your supports near the walls, if I understand what you did.

There is no problem planing a quarter inch off the "beam" unless it's already undersized. I keep getting the feeling I'm supposed to recognize this floor from another thread, but I ain't got a clue.

Can you post us a picher? We like pichers.
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