Need help with flatness of concrete subfloor

Old 12-31-06, 01:41 PM
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Need help with flatness of concrete subfloor

We are planning on installing laminate over a concrete subfloor (Ground floor, no basement, no moisture). I have been through a lot of posts and although I see references to checking flatness I need more specifics. I know the industry standard of 1/8 in 6ft or 3/16 in 10ft. How do I go about checking this? If the straight edge rocks but the distance between the floor and straight edge is 1/8 on both sides (The middle of straight edge obviously is sitting on a high spot)is that okay? If you push the one side down though the distance is actually 1/4 inch.

I have a 6ft straight edge. I assume I start in a corner and run the straight edge along the wall. Where do I do my next measurement? Move out 10 inches or so? Then do the same thing along the perpendicular wall? do you check diagonally across the room also? I have looked at a few spots and they appear to be flat but if I move the straight edge about a foot or so I can rock the straight edge and the distance from the floor to the straight edge is about a 1/4 inch.

The concrete has a very smooth and hard texture in most spots so haven't been able to really scratch the surface easily with anything manual. We have been able to take it down with an angle grinder with a diamond blade but the result was not smooth and was easily gouged. What type of tool/grinder is best for bringing down the high spots?
Old 01-01-07, 07:47 AM
Join Date: Nov 2000
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At the top of this forum is a "Sticky" Floor Prep. There are some picture links you can cut and paste into your browser.

It doesn't mater if it is "gouged" as long as you have the crown down and it doesn't matter if it is lower when your done. You can always screed over the area now and make it perfect.

They make cupped diamond wheels(not a blade/disc) that work the surface more evenly. They can be pricey.

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