How to repair an uneven concrete subfloor?

I'm going to be installing some mannington or bellawood hardwood floors in the next month. I currently have carpet and the subfloor is concrete (above grade). I plan to use the glue down method.
The problem is that the concrete subfloor is extremely uneven to a degree as much as two inches. From what I've read, this can be fixed by using a large amount of quickcrete or other type of concrete. I have no problems buying 30 seventy pound bags and leveling the floor out.
What I would like to know is what are the typical pitfalls I may run into? If I get some of the concrete mixture on the walls, is that an issue? I have floor to ceiling windows - the bottom 5 inches is metal - can I apply the concrete against the metal? What are the other issues?
I plan to live in this place for a long time and I don't mind some very hard work. I just want to get it done right.
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wow, dude! you really need to work on your math skills.
bill
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I'm having a real tough time figuring out how a sub floor in a house that already has been in use with carpet could possibly be uneven to the extent that it needs surface leveling of up to two inches. Is this leveling to even out the surface or did the whole slab sink?
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On Wed, 30 Mar 2005 04:18:52 GMT, "bill a"

No. He made a good point indicating he had read the original post.
You need to work on your IQ and social skills.
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so, PJx, you also think that one bag of mix can level a slab that's up to 2" off level?
explain, please.

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All you're given is a 2" change in elevation on his slab without knowing what the gradient or size of slab. With that you cannot calculate the volume of fill so there is no right or wrong answers. What was assumed was slab on grade is relatively smooth and flat like most of the construction jobs even though there maybe an elevation change of 2" or more from one end of the house to another. If the gradient change is gradual within the specifications (1/8" rise per 5' run, whatever) than you don't need much to smooth out he slap for the new floor. Floor contractors just smooth out the floor but don't "level" it to all surfaces are at the same elevation - unless you pay extra but the new floor don't care anyway as long as its within factory spex. The pre-existing condition was carpet on slab and OP only complains about it when it was remove so it appears to be relative smooth and flat at lease when the carpet was in place. Having smooth out (not level with respect of bring all surfaces to the same elevation) a few houses before to prep for new flooring myself, I have not used over a half of bag of fill on anyone of them. On the other hand its difficult to conceive a concrete contractor would leave 2" swimming pool on the slab that need 70 sacks (that's about 2 cubic yards!) to fill - but, again who knows without more information from the OP.

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you might want to get in touch with some folks that specialize in floor leveling. Depending on your locale, there might be companies like Elastizell, Firmfill, Ardex, etc It's pretty much like pouring a slab. Elastizell offers colors and trowelled finish, so the product could also be the finish floor. They want the pour to be about 1.5" over the highest point. Ardex is more of a polymer mix, so they can go thinner. I think manually batch mixing would be pretty tedious, and also rather difficult to control the topography across a wide area. hth bill

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"you might want to get in touch with some folks that specialize in floor leveling. Depending on your locale, there might be companies like Elastizell, Firmfill, Ardex, etc It's pretty much like pouring a slab. Elastizell offers colors and trowelled finish, so the product could also be the finish floor. "
Dude, the guy said he was putting down wood flooring, which is why he wants to level it.
They want the pour to be about 1.5" over the highest point. Ardex is more of a polymer mix, so they can go thinner. I think manually batch mixing would be pretty tedious, and also rather difficult to control the topography across a wide area. hth bill
And how many home slab floors can you raise by 1.5" over the highest point without running into major problems, like emmm doors, transition levels to other floors, etc? Doesn't sound very practical to me.
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Sound like the basement floor in my house that I leveled it a year ago. Mine was also off by 2". In my case, the floor was not level simply because people didn't level it well when the house was initially built.
I am wondering whether the foundation of your house may be settling and tilt to one side (like too much water in one side of the house washing away soil under the foundation). If that is the case, leveling the floor probably should not be your first concern.
On the other hand, if the foundation is fine and you only need to even the surface of the floor, you can use a combination of concrete and leveling compound to level the floor. I am under the impression that leveling compound cannot be too deep; therefore, you need to build up the floor with concrete before putting a layer of leveling compound over the concrete. Don't just take my words because I don't trust my own memory; you are better off finding out the exact spec in the manufacturer web site.
The thing about leveling compound is that it is expensive and we cannot put too deep. This means we should only use it for the top 1/2" to 1" layer.
The thing about concrete is that is is very cheap but we cannot put too thin a layer. This means we can only use it in areas that are offset from the expected surface by a large extent (don't ask me the specifics because I don't remember).
I used one method to level the floor. But honestly I don't recommend that method. Recently I watched a "Inside This Old House" TV show that presented a very good way to level the floor. In that show, Tom carefully scribed a piece of wood and trim it to match the up-and-down of the floor. Please go to their web site to see the details. If that is not available for people who haven't subscribed to their web site, you may search this newsgroup from my message in the last couple months about that method of leveling the floor.
If this all sounds like a lot of work to you, you are right! I did this myself, and I don't recommend people to do this -- too hard for our knees and our backs, and there is nothing to be proud of (your friends will appreciate the nice hardware floor, but they will not understand what a big deal about leveling the floor). Better off hiring a professional to do this.

DIY leveling floor will save you money only if you know exactly what to do. If you are not sure and try to trials-and-errors, you "may" end up spending more money re-doing it because undoing a mistake with concrete and leveling compound is very difficult (the leveling compound will harden to a VERY hard surface). Don't ask me how I know this.
You need to protect the wall near the floor. You may want to protect all the way up to the mid wall. Unavoidably, you will still find some spray of concrete mixture on the wall above where you have protected because of operator's error (I have some in the ceiling that I need to touch up). Luckily, you can sand those away. Obviously, you would not like that if you have already painted the wall.
This is difficult to eyeball the floor to figure out how far you need to raise the floor. We need to measure everything to find out the correct level line. You may need to use a water level or a laser level to determine the level line.
I would not want to have the concrete touching the metal window. I also would not want to have the concrete touching the wall. Leaving some space between them; you may find that you can use those space to route a cable or two. Moreover, later on you will have an easier time to replace the dry wall or the window if you need to replace them.
You definitely need to use the concrete mix that has sand in it, not the kind that has small stones in it.
Leveling compound doesn't "self-level". We need to help it along to become level with a straight edge.
Good luck with whichever way that you decide to do.
Jay Chan
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snipped-for-privacy@hotmail.com wrote:

I am wondering why we're saying level: would a tilted but flat floor be sufficient? I don't see why raising the floor up to two inches would be necessary, if all you need is flat rather than level.
<snip>

Yep, this is what I'd be tempted to do anyway. Thin pours cna be expensive, but sleepers are cheap, and lift the floor off the cement which is a bonus in my view. Still, if the OP is dead set on leveling, check out the latest issue of _FineHomebuilding_ which has an article on apply floors to concrete and IIRC a box out on leveling.
John
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In my basement floor, its problem was not whether it was tilted or not. Its problem was that there were many gradual ups and downs on the floor. When I put a straight edge on the floor, the straight edge would rock and reveal a deep space between the straight edge and the floor. This was probably good enough if I left the floor unfinished or if I put outdoor carpet on the floor. But I wanted to put ceramic tiles on the floor. Therefore, I need to level the floor.
I don't know if the OP's floor is tilted to one side or having a lot of ups and downs like my floor. If his floor is tilted to one side but otherwise is flat and smooth, I would not want to level it if I was him. However, if his floor is not only tilted but also have some ups and downs to deal with, I would just simple level the whole floor if I was him. In my opinion, this is easier to deal with a level line than trying to compensate for a tilted line -- at least conceptually.

I think you might have misunderstood my description. Actually, Tom in that TV show were using leveling compound to level the floor. The wood is for providing a level surface for the straight edge to rest on. In other words, the wood was not the primary component of the floor, the leveling compound was.
You have a good point in suggesting using a wooden sub floor to raise the floor and effectively level it. This is probably easier and less messy than using concrete and leveling compound, and the result is probably a smoother surface, and can get his feet far away from the cold concrete floor. Moreover, he can add vibration-reduction supports under the subfloor to reduce sound bouncing back and fro and make the room a good entertainment center. As long as he has enough ceiling height, a wooden subfloor probably is a better overall solution for him. In my basement, I don't have enough ceiling height; therefore, I ruled this out early on when I finished my basement.
Jay Chan
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that. Whether it's 1.5" with the cementatious fill, or .25" with the polymers, you still have either 3.5"/2.25" of fill at the low point.
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"If the OP wants his floor level, the surface has to be elevated, simple as that. Whether it's 1.5" with the cementatious fill, or .25" with the polymers, you still have either 3.5"/2.25" of fill at the low point. "
The whole point is, that it isn't simple at all, as you claim. How many home floors have you seen where that much fill was necessary or practical? And don't you think maybe someone should figure out why an existing slab floor covered with carpet would need 2 inches of leveling? Like maybe the whole thing is sinking and should be fixed correctly instead of putting a filler over it and then watching it sink again?
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the whole point of the OP's question was how to level the floor.

2" out of level on a basement slab is not especially unusual. A few reasons why a flatwork crew ended up with the slope: 1) Intentional, for drainage to sump, etc. 2) Unintentional, didn't bother to shoot grade lines. 3) Unintentional, a little short on the concrete load. 4) Unintentional, not enough manpower to wheelbarrow sufficient mud to the far end of the pour.
>And don't you think maybe someone should figure out why an

pretty much doesn't matter.
>Like maybe the whole thing is sinking and should be fixed

going to sink and the slab will not. If this is happening, the slab is going to be (obviously) breaking all over the place.
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. "2" out of level on a basement slab is not especially unusual. A few reasons why a flatwork crew ended up with the slope: 1) Intentional, for drainage to sump, etc. 2) Unintentional, didn't bother to shoot grade lines. 3) Unintentional, a little short on the concrete load. 4) Unintentional, not enough manpower to wheelbarrow sufficient mud to the far end of the pour. "
Did you even bother to read the OP? He specifically said it was an above grade floor with existing carpet, that he wants to put wood flooring on, not a basement floor.
And don't you think maybe someone should figure out why an

pretty much doesn't matter.
Only an imbecile would think it doesn't matter how it got this way, or how it's even routine that an above grade living space slab that's presently carpeted could require 2 inchs of leveling before installing wood.
"When a building sinks, the footings and columns (where the weight is) are going to sink and the slab will not. "
It's entirely possible for a portion of the slab to sink, with or without the footings sinking. For example, if the footing area was done correctly, but the base for the floor was not compacted correctly, the floor will sink independent of the footings.
"If this is happening, the slab is going to be (obviously) breaking all over the place. "
Hmmm, did you even bother to ask if there were any significant cracks before telling him all he had to do was apply 2-3 inches of leveling material as a solution before laying down the new floor?
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The previous owners of my home built a enclosed addition on an existing outside porch. The floor is smooth, but unfortunately not level. It drops approx 3" over a 10-12 ft run (most likely to handle any water/rain). Similar to the orignal post, I'd like suggestions on the "right" way to level my floor. Walls are drywall.
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Why level it?
If it's flat, you can put flooring on it. If you're installing a pool table, shim the table. I'm hard pressed to think of a reason to mess with a flat slab in good condition, simply becuase it's got a bit of a grade for drainage.
John
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