leveling basement slab - UP TO 3"!


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Old 11-05-14, 05:44 AM
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leveling basement slab - UP TO 3"!

Hello all,

Long story short. I'm stuck with a home that had MAJOR water issues. Considered suing the seller. Cost to litigate was too much, with no guarantee of winning, not to mention trying to get money from the seller. Circumstances mitigated getting an inspection before purchasing, and I'm now paying for it BIG TIME!

The basement slab had HUGE voids underneath which caused large cracks and heaves. I had a company fill the voids with expanding polyurethane, and now the slab is at least fully supported from underneath, and I have fixed all of the outside water issues.

I now need to level said slab. At the extreme end of basement, there is around a 3" slab elevation drop. Obviously, using a leveling compound would be first choice here, but at around 30 bucks a bag, I simply cannot afford to go that route. I'm talking about half of a 1200 sq. ft. basement here.

I've decided to simply use a bonding primer, and then use concrete to level the slab. I'll have to feather into the existing slab, and I'm aware there will most likely be cracking in those areas. Don't think that will matter, as I will be putting down a laminate wood flooring over top. I've also been assured that due to the nature of how the polyurethane works, the existing slab will easily be able to handle the additional weight of the new concrete, especially because it will be spread over a large area.

Question: Do you guys or gals have any other suggestions as to how I could level this slab, OTHER than using a leveling compound(which I cannot afford), or concrete, which will certainly be a big pain. I know it's crazy, but what about just using some silica sand, and simply pouring over and compacting. I'll be putting a moisture barrier under the laminate anyway, so... would the sand be just simply out of the question?

Thanks for any input,
Marc
 
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Old 11-05-14, 08:31 AM
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Starting from the beginning I would have considered mud jacking which would have filled the voids under the slab and also can return sunken sections back to level. Now that you've filled under the slab with foam and are obviously going to finish the room I don't know why you are getting cheap on the leveling compound. Do a crappy job with the leveling and you'll be back here in 6 months saying your laminate flooring is buckling, popping and uneven. I'd say do each step of your project properly. If you don't have the money then you can't do the project or need to do it in stages as you get the money but start from the bottom up doing it properly. Putting down finished flooring over a poor base could end up wasting all the money you put into it.
 
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Old 11-05-14, 09:02 AM
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I don't think that you can use SLC in a three inch thickness. When my sister had a new engineered hardwood floor installed in her house the family room had a dip of about 1-1/2 inch in less than ten-twelve feet. The flooring installer said regular SLC would crack at that thickness and ruin the floor so he had to get some kind of two-part compound that had fibers or something to keep it from cracking. That stuff was expensive, as I recall something like $700 or more for just the materials.
 
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Old 11-05-14, 09:54 AM
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You have decided to finish that space into something, but if you search this forum you will find many threads about the ensuing problems.

Moisture problems come in several forms and under different circumstances. Most existing homes were never built to provide a basement space without moisture issues and I'm talking beyond liquid water. Moisture vapor passes right through concrete and can wick up from below the footings to the top of your foundation. When you finish the inside walls you will need to address that moisture as well as the summer humidity condensing on the cool inside walls.

I've just touched on some of the problems people have discussed here, but my point is, before you bust your budget leveling that floor, continue the design process to see what else will be waiting for you. Basements can end up being some of the most expensive living areas in a home and all too often still smell like a nasement.

Best
Bud
 
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Old 11-07-14, 05:57 AM
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Polyurethane injections are far superior to mud jacking. Basically the same concept though. Mud jacking is known to break down over time, while polyurethane, when NOT subjected to ultra violet light(sun), will last virtually forever,... plus, the polyurethane will support MUCH more weight.

I was not able to achieve "lift", due to the fact that the slab is tied into the foundation, as opposed to a "floating" slab.

The expense is only one aspect of my not wanting to use a leveling compound. I can't seem to find anything that states it can be used for anything beyond 1", which leads me back to maybe just using concrete. I am under the impression that as long as I get the concrete reasonably level, that it won't really matter if I get some cracking underneath, due to the fact that it will all be covered with moisture barrier and flooring.

Thoughts?
 
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Old 11-07-14, 08:37 AM
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you might consider using a bonded grout leveling layer instead of slc,,, naturally you'll have to properly prep the existing floor 1st
 
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Old 11-07-14, 04:57 PM
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Laminate would be the last flooring I'd chose in a basement and is not going to work over a cracking floor.
 
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Old 11-07-14, 07:01 PM
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To level the floor, I'd consider using a simple, bonded concrete overlay. You'd need slightly less than 5 yards of concrete, costing less than $600 in most markets today (based on one-half the 1200 S.F. being overlaid, at an average of 2-1/2" thick).

Don't make the mistake of trying to feather-edge any of the new concrete--a sure recipe for failure. Much better to chip down and remove any excess, such that the overlay is at least an inch or so thick at its thinnest locations. If you break the pour area into four equal quarters, using forms set to finished grade, you'll have a much easier job finishing, and won't have to mess with any false forms.

If you've never placed or finished concrete, I suggest you either consider paying a concrete crew to do it for you or enlist some buddies with adequate concrete experience.
 
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Old 11-08-14, 06:58 AM
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Why would laminate be your last choice? It's impervious to moisture, so it would seem to be the ONLY choice. Please elaborate.
 
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Old 11-08-14, 07:02 AM
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By "bonded concrete overlay", I assume you're talking about using a bonding primer over the existing concrete, then laying down additional concrete, correct? If so, that's exactly what I'd planned on doing.

I'd also thought that I'd maybe use concrete for the extreme area's (2-3"), then after that cures, go back and smooth everything over with a leveling compound. That way, maybe I could leave the edge of the concrete thick enough so it wouldn't crack, then, feather in with the SLC, no?
 
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Old 11-08-14, 07:09 AM
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Sorry guys, but I still don't understand why, if the concrete cracks at the thinnest areas, it would matter,?... given that the concrete itself, which is under the flooring, can't really go anywhere. I mean, would it cause the laminate pieces to perhaps buckle? If so, why. I really can't visualize what, or how that could happen.
 
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Old 11-08-14, 09:18 AM
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Why would laminate be your last choice? It's impervious to moisture, so it would seem to be the ONLY choice.
I have never heard of any laminate flooring that was impervious to moisture. Most specifically state they are NOT to be used in areas of high moisture content. Please provide a link to the product you intend to use.

Sorry guys, but I still don't understand why, if the concrete cracks at the thinnest areas, it would matter,?...
Would you lay a floor over a layer of dirt that was on top the concrete? Because it is the same thing if the thin overlay cracks. In either case there is no substantial backing to the finished floor.
 
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Old 11-08-14, 10:26 AM
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"I have never heard of any laminate flooring that was impervious to moisture. Most specifically state they are NOT to be used in areas of high moisture content. Please provide a link to the product you intend to use."

Well, you are correct,..I was mistaken for sure. I went back and re-read the info of this particular laminate flooring, and it only says it's OK for below grade, which a basement obviously is. Geez, and I have two pallets of Allen +Roth laminate flooring waiting in my basement. I did have water issues when we first moved in, which was last November. I remedied those problems, and have had no further water enter the basement since, and we have had some massive rains.

I thought I was getting the right flooring. The basement is going to be converted into a recording studio, so I needed something that looked like wood, but I knew I couldn't put actual wood down there. As long as actual water doesn't enter, do you think I'll be OK? I did obviously plan on putting down a sufficient moisture barrier. I also run a dehumidifier, and it has kept the humidity below 50% all year.

The manufacture states that occasional spills will not harm the flooring. I even read where an owner said that one piece of this flooring had fallen behind a bush,.. and was in the elements for months, and still looked like new...so maybe I'll be OK?

Anything else I could do in addition to a moisture barrier and dehumidifier to maybe assure there are no issues with the flooring?,... barring no water pipes leaking, etc.
 
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Old 11-09-14, 05:14 AM
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I had another idea regarding leveling the slab. Since it's clear that the cement will need to be at least 1" thick in order to prevent cracking,(no feathering)...what if I were to affix a piece of 1" thick wood strip from side to side, basically making a large form, with the 2-3" area at one end, and gradually ending at the 1" wood form.

I would then of course use a cement bonding primer, and apply the cement. After curing, I would then remove the wood form. Then I will use a self leveling compound, starting at the 1" edge of the cement, and feathered into the remaining slab.

Would this work? Just thought this method would be far easier than cutting and removing/chipping away concrete such that I would have the aforementioned 1" thickness.
 
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Old 11-10-14, 12:39 AM
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That sounds like a better plan, as I understand SLC can be feathered but I have never actually worked with the stuff.
 
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Old 11-10-14, 04:59 AM
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we've done this several times using polymer-modified cements extended w/clean 3/8" stone - not cheap but never any unbonding + it can be feather-edg'd,,, products were elitecrete's thinfinish & texturepave
 
 

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