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ehuesman 11-26-2007 11:09 PM

Prepping concrete subfloor for laminate
I plan on installing about 1000 square feet of laminate over the majority of my first floor, which is concrete slab. The majority of the floor was previously covered in ceramic tile. I have most of that up now (talk about work). Some of the floor was also previously carpeted.

While taking up the tile and thinset (BTW I used a demo hammer and 6" floor blade), the concrete slab got some small chips in it, it looks kind of like pock marks. Most of them are about 1/4" wide and 1/16" deep. Also, when I took up the tack strips in the carpeted areas, I got what I would describe as "divets" of concrete that came up with the strips.

I keep reading that the subfloor needs to be "flat, level, and clean" before installing the laminate. Does it have to be smooth as glass? I'm hoping that the right thing would be to use some sort of patching compound for the larger "divets" and hopefully not have to do anything to the "pockmarks". There are also some small ridges where the thinset didn't scrape clean off the slab. These ridges are 1/32" to 1/16" high. Again, how smooth does it have to be?

Also, I have a long crack across the slab. It varies in width between hairline and 1/16" and has no difference in height. The underlayment I'm using has a vapor barrier, so do I need to caulk this crack?

BTW, the laminate is a Mohawk 9.5MM and I'm using the Floor Muffler underlayment.

Thanks in advance for everyone's help, and if I have this many questions in the "prep" phase, imagine how many I'll have when I get started :huh:

Chris Johnson 11-26-2007 11:17 PM

Roll out the foam and go, little pock marks are nothing to worry about. The crack sounds like nothing (No Moisture). The floor floats and unless you have big divots you won't have any problems, make sure you tape the seams of the underpad so it doesn't seperate or ride on top of itself.

Krichton 11-27-2007 04:20 AM

This all seems like alot of work and money just so you can install something that may actually depreciate your house.

ehuesman 11-27-2007 12:44 PM


Originally Posted by Krichton (Post 76574)
This all seems like alot of work and money just so you can install something that may actually depreciate your house.

Someone can feel free to correct me if I'm wrong, but I don't think replacing standard 12"x12" ceramic tiles and old carpet with a top of the line laminate is going to depreciate the home value much, if at all. And besides, all the appreciation/depreciation in the world doesn't matter if I don't like what I have :wink: .

MinConst 11-28-2007 06:45 AM

I would scrape off the ridges and not worry about the divots as long as they are small like you mentioned. Put a layer of 6 mil poly down first then your pad, and go to town. Don't forget to leave a good 1/4" to 3/8" space along the perimeter.

Krichton 11-28-2007 10:28 AM

Why would you buy top of the line fake wood laminate which I assume is very costly when you can have real hardwood?

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