Leveling extremely uneven floor

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  #1  
Old 02-12-18, 08:41 PM
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Leveling extremely uneven floor

Hello,

I am working on converting part of my basement into an office. In doing so, I have come to realize that there is an extremely aggressive slope running toward one side of my basement. There are areas where it's easily 4" lower.

My original idea was to use leveling compound, but realized that it's not made for the thickness I need, and is also extremely expensive.

The next solution was to use cement, but I then realized that it was too thick, and wouldn't feather very easily in the spots where it's extremely low.

I then tried to scribe some 2x4's, but was unable to cut the scribes evenly, and made a terrible mess.

The end result I came up with, was this: (included in the attachments section)

I took 1x2 furring strips, laid them down flat on the high side, and shimmed them up to level on the low side. There are 2x4 blocks and or shims about every 6" or so but now I am worried that even with the 3/4" osb on top of it, the furring strips are not strong enough to support weight.

Would the setup I have work for what I am trying to do? Another alternative may be, although extremely expensive, is to use the furring strips as guides, pour new concrete between them, and screed the entire floor level. Considering the room is 8.5ft by 14.5' long (the furring strips are running along the 8.5ft section), and parts of the floor are 4-6" lower than the rest, it may result in an extremely large amount of concrete being poured. which could get costly. By my calculations, that's about 106 #60 bags, at $5 a bag.

Would the 1x2 furring strips work for what I need it to? (Perhaps if I add some more supports under the higher parts, but I think the 3/4" osb may offset some of the load and dispurse it evenly over more of the strips at once. I centered them at 16" on center.

Sitting on top of the 1x2 furring strips is going to be the bottom plate of the 2x4 wall. The 2x4's under the furring strips were to level the floor from right to left (in the image), as it had two different slope angles going in different directions.

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Last edited by PJmax; 02-12-18 at 09:12 PM. Reason: reoriented picture
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  #2  
Old 02-13-18, 12:38 AM
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The problem is your using a material, furring strips, on a floor especially if you embed into concrete that should be kept off a floor.

You mention concrete, that is clearly the best material to use and once cured self leveler could be applied to finish it up.

An alternative filler for the low spots would be cement board stacked up, mortared in place then self leveler!
 
  #3  
Old 02-13-18, 05:57 AM
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Moisture/water vapor coming up through the concrete slab will cause the untreated furring strips and wood blocks to rot. Trapped underneath the floor you're creating a dark and damp space which is perfect for destroying wood. You should never use untreated lumber in contact with masonry. The bottom plate of your framed wall should be replaced with pressure treated.
 
  #4  
Old 02-13-18, 06:19 AM
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It doesn't matter either way, most of this needs to be tore down. I continued laying the strips out in this manner to see what I ended up with, and at the lowest point there's an 8" height difference. There is no way in hell I can scribe sleepers or even do anything to bring that back up to level. I am not going to spend $2,000 dollars to fix somebody elses screw up, that should've been fixed before. I understand that there is supposed to be somewhat of an incline there, but 8" in one direction and 4" in the opposite is just ridiculous and poor craftsmanship.

Also, the lumber sitting on the slab is pressure treated. The furring strips aren't but they weren't being permanently fastened yet either. I was trying to get a feel for how high I would need to go.
 
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Old 02-13-18, 06:55 AM
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If you are so inclined, tearing out the cement floor and repouring a level one is the best and only good solution to this problem.

They may have done it this way if the floor occasionally got flooded. Is there a sump or floor drain anywhere?

I just guessing but I wonder if that floor is not very thick? Have you drilled it or busted through it anywhere?
 
  #6  
Old 02-13-18, 08:05 AM
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Again, there is no way I am spending that amount of money to fix this. There is no drain in the floor. There is a cleanout back there, but no physical drain. My guess is that they did it so that all the water would pool in the low spot, and you could pump it out rather easily. The floor is heavy and thick. When using the Powder nailer to tack the ledgers to the floor, one didn't shoot through all the way and chipped the concrete, and you can see at least 4" down in thickness.

The cement is smooth and no cracks, so I can tell you with almost 100% certainty that it didn't settle this way, it was built this way. Concrete doesn't really 'bend' without cracking.
 
  #7  
Old 02-13-18, 09:01 AM
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If you have enough headroom you could build a platform like a deck. Use pressure treated for the structure. Since you can support below wherever you need to prevent bounce, 2X4s on joist hangers should be enough on 16 inch centers. The 4 to 8 inch gap at the edges should be enough to allow ventilation and prevent moisture buildup
 
  #8  
Old 02-13-18, 03:42 PM
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This isn't a terrible idea, although I have vent work and etc that is causing me some tight headroom as it is now so I am worried adding another 6 inches (2x4 + underlayment + padding * carpet) or so will make it unbearable. I am also not sure how I would support the bottom of the 2x4's where it's not level, either.

I did find that if I use a 2x6 instead of a 2x4, I can scribe it a little more accurately. I am going to pick up a couple pressure treated 2x6 boards tonight and scribe them then rip them down with my circular saw to see if that works. I think the biggest problem is I am fighting with slope in two directions, not just one.

EDIT: It's not a significant gain in height (only 2 inches), but is it possible to build the platform using 2x2's instead of 2x4's, or do 2x2's lack the structural support to be used as load bearers? They need to span a distance of a little less than 8 feet. I could even space them 8" on center so there are more of them if it will help with support

Was thinking of maybe using 2x2 furring strips (with a plastic vb underneath), or AC lumber with these hangers:

https://www.homedepot.com/p/Simpson-...RSP4/100375038
 
  #9  
Old 02-14-18, 08:43 AM
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You could use 2X4s laid flat. You would only need to use PT for the ones that lie directly on the concrete (even with a vapor barrier). Otherwise use standard lumber with PT for the leveling blocks. Provide supports every 4 feet. Use tapered shims (wood shingles) to level.

How big is the room? A sketch showing the slope would help. Note the slope as 0, -4, -8, etc. at the corners and at a couple of places near the middle.

If you are concerned about the floor shifting from side-to-side because of the slope and causing the walls to go out of plumb , you could consider building the walls on the existing concrete floor, accounting for the slope by adding additional sill plate and blocks below the sills as needed, and then building the floor inside the walls (instead of building the walls on top of the floor.

If you are concerned about the height even with 2X4 laid flat, I have some ideas that would gain 3/4 inch by recessing the subfloor into a rabbet in the 2X4 or by creating a sort of inverted tee structure from 1X stock.

Do you need or are you pulling a building permit for this work? An inspector would probably not approve some of these ideas.

I don't understand how you intend to use the stud plate tie.

Commercial grade rubber-backed carpet squares are a great alternative to standard carpeting in this kind of installation and are only 1/4 inch thick.
 
  #10  
Old 02-14-18, 09:54 AM
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No, this is not being inspected and a permit has not been secured. It would've cost me 8x to cost to do it to code because of all the problems I ran into along the way.

here is a rough sketch of the basement with the room dimensions as well as what I had planned to do with the hangers I linked: (in attachments below)

The red circled area is where the fasteners would attach. They would be on the underside of the platform, similar to how joist hangers are. Since 3/4 of the platform will be mostly on the flat surface of the cement floor, and wedges will be cut to secure the 2x2's at the low spot I don't think using these will be too much of an issue. I had planned to space the 2x2's 8-12" o.c.

The numbers indicated on the right of the rough floor dimensions indicate where the worse slope values are, and the light grey lines indicate the direction the slope goes, with the three lines converging at the end-point of the slope.

I already have all four walls up, I am just working on the floor, now. I was able to run a ledge level from the front to the back to set the remaining walls on. Now I am just working on building up the foor inside of the room.

I was considering using the carpet tiles, but was worried about #1 sound, and #2 padding. I also wasn't sure if they made a somewhat thicker pyle in carpet tile, as all the ones i've seen are low pyle and dont have much texture to them.
 
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  #11  
Old 02-15-18, 09:43 AM
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So the floor is level up to the area where the grey lines are?

In that case you can use 2x2s at 16 inches on center on a vapor barrier for the level area and just deal with the sloped area differently.

Is there a wall at the corner where the slope occurs? If there is you could nail a ledger to the wall to support the ends of the 2x2s over the sloped area. Place a PT 2x4 or 2X6 ripped down if necessary) under to support the span of the 2x2s. Follow the slope, i.e. Place the support at whatever angle necessary (relative to the wall) to keep it on a constant plane of the slope.

Or think of the floor over the slope as a hatch (removable if you need to get to the clean out). Build a frame that hangs from the wall and/or rests on the concrete floor and build a hatch cover out of 2x4s supported on ledger strips around the inside of the frame.
 

Last edited by 2john02458; 02-15-18 at 10:59 AM.
  #12  
Old 02-15-18, 11:18 AM
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Attached is an image of how I would be using them, except they would be horizontal instead of vertical. They would also be facing down to the concrete not facing up towards the underlayment. I am also going to use the screws instead of the nails to hold them together.

Those fasteners are essentially just to hold the framing together. The support will come from when it's attached to the walls, and from underneath in the low spots using the custom scribed wedges/blocks to level it out and support it.

You still don't believe that would work?
 
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  #13  
Old 02-15-18, 12:52 PM
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Should work to hold the framing together. I was concerned that they wouldn't be supported from below and the ties would bend.
 
  #14  
Old 02-15-18, 12:57 PM
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My apologies for not clearing that up. I wasn't meaning to use them as 'joist hangers' as I originally referenced them, it was the only thing close I could think of at the time to provide meaning for what I was trying to do.

Essentially, they are just to hold the framing together. The weight will be supported by the screws around the perimeter which are screwed into the wall studs around the room, and also from underneath via shims where the gap isnt very big, and custom scribed wedges (shaped like triangles mosly, that match the contour between the floor and the bottom of the 2x3).
 
  #15  
Old 02-15-18, 07:20 PM
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Attached is the progress from today. It's only temporarily fastened in. You can see how high it's off th ground in order to be level.

I need to finish building the stringers, then make the blocks to go underneath, then I can finally finish.
 
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  #16  
Old 02-16-18, 06:57 AM
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It's hard to tell...did you say you fastened a ledger to the wall studs to support the floor? I don't see what the purpose of having the 2x4 around the perimeter like that. Couldn't you have laid the ends of the floor "joists" on top of the ledger and nailed through the top of the joists into the ledger? That would eliminate a lot of hardware/brackets. Guess I don't understand why you wouldn't use larger lumber or at least stand the 2x4's on edge. Looks like you have plenty of space. I can't see the opposite side where the slope begins though (can you post another pic?). Laying the joists flat regardless if you are going to support them every 4 feet, doesn't seem like the best method. What is your subfloor to ceiling height after doing so?

As far as scribing, couldn't you just lay your boards on end on top of the slab, secure them temporarily, snap a level chalk line down the length, then rip them with your circular saw? This would give you a stronger floor and you wouldn't need any supports. Notch the ends so they rest on top of your sill plates and nail the joists into the sides of the studs. You wouldn't need any brackets, hangers, etc.
 

Last edited by mossman; 02-16-18 at 07:14 AM.
  #17  
Old 02-16-18, 07:18 AM
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That side, actually has two bottom plates. One of them is shimmed and wedged underneath to make it level from the front of the room to the back, then the actual bottom plate for the wall with the studs attached sits ontop of that. This ensures the wall itself is straight from front to back.

It's actually a 2x3 that acts as an end plate for the joists. The reason I didn't sit it ontop of the bottom plate for the wall is because of the difficulty of shimming each individual one. Building it this way ensures that I can raise all of the joists up to the same height and level it as one piece. There is no ledger underneath the 2x3. What WILL be there, are some wedges that fill the gap between the bottom of the sideways 2x3 and the floor.

The reason I didn't use 2x4s is mainly the cost for what I am doing. The 2x4s were 4 dollars a piece while the 2x3s were a dollar a piece. It doesn't seem like a big difference but for the minimal gain in stability and the number I need to do it, it was a significant savings. The 2x4s need to be laid sideways just like the 2x3s are now, so thickness was no different. the only difference was the width of each board. I cannot stand them up, as I would have lost an 4" of space standing them that way. With the way the slope is now, if I stand on the raised side of the 2x3 platform, my head is about 3" away from the vent above. That's before the underlayment, the carpet tile, and the spacing for the soffit framing and drywall that's going on it. If I were to use a 2x4, there would be no way I would clear headroom. and I am 5'7". Somebody who is average height already stands no chance at being in this room.
 
  #18  
Old 02-16-18, 07:29 AM
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As far as building a subfloor, nothing you have done would pass even the nearest code as far as I'm concerned. There is absolutely no reason to use such skimpy lumber when you have all the room in the world to use beefier stock. An stop with the saving money stuff. You really think that this floor will do anything but flex under the weight of furniture, and a persons body weight. To me, you are doing nothing but wasting your time trying to save a buck. A little research into a span calculator for subfloors will tell you that the stock you are using isn't even mentioned because it is insufficient for the function you are using it for.
 
  #19  
Old 02-16-18, 08:39 AM
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Again, what you are not understanding is I DO NOT HAVE ROOM! If I use a 2x4, I will NOT clear the ceiling. What I am doing, is what I have to do in my situation. You may not agree with it, but that does not make it any less effective than what you 'propose' to do. After the lumber is in and wedged and supported correctly from underneath, it will not be any less stable or hold up any less than using a 2x4 standing on end, which I would have to wedge and support from below as well anyway, except I will gain an extra ~2" of headroom, which is already cramped as it is.

Aside from digging up and repouring the concrete in the basement to level it, nothing would pass code so that is irrelevant.
 
  #20  
Old 02-16-18, 08:49 AM
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I have to agree that there is a better way, and from the looks of it, you have plenty of room to go with larger lumber on-end (the way a floor should be built), at least on the side you show in the photos. I really think you should re-visit the scribing method and do this the proper way so that all joists are laying on-end and fully supported by the slab underneath. IMO, you do not want any portions elevated, especially not 2x3s laying flat. Perhaps you could use 2x4s (on-end and perhaps doubled up) for the more shallow part, then switch to at least 2x6 or even 2x8 as the floor drops off. What exactly is the issue with scribing and ripping the boards while they are in place?
 
  #21  
Old 02-16-18, 01:15 PM
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I just read over a couple of your posts. You said it slopes 8" in one direction and 4" in the other. IMO, the easiest and best approach would be to use 2x8 joists and rip them. Build your walls first then lay pressure treated 2x4s flat against the slab and nail them in place with cut nails. Next, snap chalk lines on the walls around the inside perimeter of the room to establish a level reference line representing the top of your floor (minus 3/4" subfloor). Then, lay out your 2x8s on top of your 2x4 sleepers and tack them in place (nail each end into a wall stud). Now snap chalk lines along the length of each joist using the chalk line on your walls as a guide. Lastly, rip the joists in place with your circular saw, or remove each joist and rip it using your saw horses to make it easier on yourself. If you're going to rip them while they are on the floor, make sure the joists on the high side are tall enough to allow your circular saw to make the entire cut without running into the slab. You can use regular, non-pressure treated for your floor joists, since the pressure treated 2x4 sleepers give you the separation. Sounds like maybe you can get away with 2x6 lumber, especially since the 2x4 sleepers will add 1-1/2".
 
  #22  
Old 03-04-18, 02:26 PM
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unbonded conc overlay would've been the least expensive &, from the length of this thread, the fastest,,, not necessarily a diy project for most, tho
 
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