concrete subfloor prep for Kahrs floating floor


  #1  
Old 08-08-04, 03:57 PM
smapple
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Exclamation concrete subfloor prep for Kahrs floating floor

Help---This is getting to be too much of a point of disagreement between my wife and I. Comments are welcome and appreciated.

Here's the story so far. I discovered I had thick-set mortar in the hall area between two room areas, and desired to cover the entire surface (two rooms separated by a hall in the entry way) with wood flooring. My wife chose Kahrs wood flooring for its obvious value and attributes. I have laid the flooring in one room, and am approaching the hall. It's beautiful. Now the problem:

The Kahrs specifications states that the floor cannot vary by more than 1/8 inch across 8 feet. OK, I accept this. To alleviate the difference in heights between athe hall way and the two rooms (dining room and office each on opposite sides of the entry hall), we dug up the old tile, thick set mortar, and hired contractors to come in and pour new concrete in the well that the removal created. Problem is that they made it too HIGH in a couple of spots. Too low is OK- we can just Ardex it in, but I have now rented a concrete wheel for a hand-grinder, and then a concrete surfacing machine, and I am still not where I need to be. Neither made even a dent in the concrete. It's really good, strong concrete.

I believe I can simply pour enough material in to bring all srfaces up to the proper level, and perhaps put a transition joint at the edge of one room. I'd then feather the direction of the lower spots to meet the spec of the 1/8 inch per 8 feet. Problem is that my wife believes this cannot be done, and we must just bite the bullet, chisel out the concrete in the high spots, and re-fill. I worry that chiseling (jack-hammering actually) could cause a concrete crack and/or greater problems. I've seen these concrete gougers that you can rent, but they have two problems- you must BUY the new chisel tools for them- at about $100, and they won't get close enough to the wall- which I don't want to tear out just to make the flooring work.

Many have recommended Ardex- I can tell you it works well for the spots where I've used it already, but it's really finicky to work with. You get a few minutes, and it's set. You have to be fast, and ready when it is. It's still runny enough to drip off your trowel onto areas you've already finished, but not runny enough to re-form once it decides to set. Self-leveling is a misnomer. And it's so expensive, you don't want to use it everywhere. 1/8 inch in 8 feet is a spec that is not even met by high-quality lumber. I guess that's how the contractors missed the spec? Try finding a screeding tool that eill get you to that spec, I dare you. And then try finding one that will get between walls in a hall, etc. etc. OK, I've sufficed with a measure and trowel technique, but even then, you can get a hump- heck the pro's missed a major one, and that's how I got here.

Where does the answer lie? Any experience with putting down Kahrs? Of course, the Kahrs help line just tells you it has to be baby's butt smooth, and I understand their desire to cover their behinds. They recommend you use layered tar-paper to level out the uneven spots. This seems like a slippery solution, and not one that would bear the test of time.

Steve
 
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Old 08-09-04, 08:48 AM
H
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Steve:

I'm sure others can assist om this one but this concerns me..."and hired contractors to come in and pour new concrete in the well." It better be cured, otherwise that floor will begin to look strange with cupping and other things you don't want. Has the moisture content been checked?
 
  #3  
Old 08-09-04, 02:26 PM
smapple
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concrete subfloor prep for Kahrs floating floor

Yes, moisture has been verified. It has been installed and cured for about 3 months. IN fact, it hac cured so hard that it rejects any grinding materials I try to throw its way. Thus the dilema. We're so upset about it that we're actually beginning to think that concrete doesn't really look that bad...i.e. maybe we don't need those wood coverings after all. Bare concrete doesn't care if it has a couple of humps in it.
Steve
 
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Old 08-09-04, 08:00 PM
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The specification is really a flatness spec, not level. In a sense I could say that one mans high spot is another mans low spot. When you level a floor you are really looking for the low spots since that is a lot easier to correct. I seriously doubt that you floor is entirely flat with 2 bumps.

Why don't you take an 8' level and go over the floor and mark the low spots. Do the fill (do one or 2 patches at a time to avoid the setting problem you described) and then recheck for level - do again if necessary. Even if you have a high spot of say 1/2", if you can spread that out over 10-15 feet or so you will meet spec.

You might say that you need 4x8' to correct a 1/2" high spot but this is not really true. You correct it within 8' around the high spot then go to the next 8' (overlap by about 4') and that will be a lot less than 1/2" if you follow me correctly.

How high is the bump?

And if you think Ardox is a pain I know people who have really messd up slabs with the self leveling method. At least by the patching method you can only mess up a small section at a time and I did it nearly perfectly the first time with no previous concrete experience. No patching cement feathers to a real fine edge but you don't need that for floating anyhow.
 
  #5  
Old 08-10-04, 06:45 AM
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Hit it with a diamond blade mounted on an angle grinder. Or you can rent a concrete grinder, that has diamond wheels, Looks like a big floor buffer.

Sounds to me like the concrete guys didn't finish the job right, have you asked them why they poured it too high? Sounds to me like it is there job to make it the same height as the slab around it.
 
  #6  
Old 09-06-04, 10:28 AM
smapple
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Let's talk grinding floors.
First I rented an angle grinder. It cost avour $40, and I had to buy a $10 disc. It didn't work- despite the home depot guys claims to the contrary.
Next, I rented something called a "concrete finisher". It cost $75, plus I had to buy three "stones" at $7 each, and it was also worthless- plus it only gets up to about 1 inch from the wall.
I looked at the concrete "grinder" machine. It only gets about 3 inches from a wall. It costs $100, and you have to buy $150 worth of new stones to use it. You can't just use the last guys worn stones. I think the guys at the rental place use them up for the jobs they have around the house.
The guys who rent hand-grinders don't have diampond-tipped wheels available for them, at least not at Home Depot, or Lowes.
I'm now considering putting a ceramic cutting blade in my circular saw and cutting a series of grooves followed by a chisel. I'll then refill with ardex to level the whole area.
Actually, maybe concrete floors don't look all that bad... I'd just need to get rid of all this unused flooring I've got laying around.
I'm seriously considering just pouring a whole new layer of Ardex and being done with it all as per the earlier suggestion here on this link. As you can see, I was trying to avoid that- for other reasons that I haven't detailed.

Any other comments welcome!
Steve
 
  #7  
Old 09-07-04, 09:09 AM
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The diamond blade in the circular saw, is your best idea yet. Expect lots of dust!
 
 

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