Hello all!

My name is Tim and I'm new here and this my first post after much lurking. I've read many threads regarding concrete floor flatenning before hardwood installation. I'm in the process of evaluating a bedroom for a hardwood floor. It is a bedroom 10'x12' with no moisture problem and no cracks in the concrete. The house is 25 years old. My question is regarding the best method of flattening the floor.

I've drawn a grid on the concrete and made measurements at 154 locations roughly at 12" intervals using a combination square and aluminum extrusion across concrete as a flat reference.

I've plotted the outcome and basically about 20% of the floor is 6 to 8 32nds of an inch out of flat. About 30% is 4 to 6 32nds out of flat with the remaining being split evenly between 2 to 4 and 0 to 2 32nds out of flat.

It appears I would need to use a self leveling compound but I'm a little reluctant as I've never used it before and 15 minutes doesn't seem like much time. I've attempted to locate someone locally to do the flattening without success.

I would appreciate any and all input on how to proceed.

Sorry for the long post!

Best regards,
Tim Tritt in Oklahoma

When scraping concrete and because it is porous, your not going to get the contaminates out of the pores.

After I grind the high spots of the slab and then fill the low spots of the slab, I then flat trowel skim coat a thin layer of Ardex SD-F Feather Finish, or Mapei PlaniPatch, to encapsulate any contaminates left in the pores of the concrete.




First scrape all the contaminates down to a residue.

Here I'm scraping thick paint where they stood all the doors up in the f
amily room to paint them, during the new construction.










Here is a pile of trash I scraped off what looked like a fairly clean slab.










Here I set my 10 ft. aluminum screed/straight edge on the surface of the slab. Looks like it needs some filling, or we are going to have massive hollow spots and popping and creaking. I mapped out just where it dropped off into the swimming pool.







Ok, after mapping out the low spots, I mixed up my mud, in a 5 gallon bucket. Grabbed my screed and went to work, pouring and dragging my screed.
Here is my first pulls. I have to let them set up before I can do more, as you can't drag on top of wet mud, or you will mess up what you have done.









After the above set up I scrapped any lumps or ridges left by the screed, and feather edge the edges, swept up and vacuumed, again.
Then I finished pouring and dragging my mud to fill this massive low spot, that was like a trough across the entire room.









Then once that set up I scraped the lumps and the ridges and feather edged, again.
Then I skimcoated the entire surface to make it FLAT and encapsulate any contaminates in the pores of the slab.











After letting that dry and cure for a couple of days, I was ready to pop a line and start gluing planks.











Taping the planks in place as I work across the room, makes for a tight, gapless installation.











When finished, wipe the floor down and look for glue smudges to wipe with mineral spirits, then put your transition moldings on and let it sit overnight. Then next morning, pull blue tape and wipe down the floor, making sure to get any glue smudges with mineral spirits, wiped off immediately.







Hope this helps out.

Floorguy,

Thanks for the reply and great pictures!

I have a couple of questions:

1. What process do you use to "map" the low spots?

2. You mentioned "mud", what exactly do you use?

Thanks,

"I mapped out just where it dropped off into the swimming pool. "


Right where the concrete drops and is not making contact with the slab, I draw a short slash on the concrete. Move the straight edge over about a foot and make a slash, move the straight edge and make a slash.... Connect the dots. I call it a swimming pool, because it is never a round circle, or a square.



There are many cement patching compounds out there. I like Mapei, PlaniPatch, or Ardex SD-F

Floorguy,

Thanks again for your input!

Regarding the "mud" I just wasn't sure if you were using a SLC
or something else. So it's ok to level a small area and then go over
it after 24 hours with more?

BTW here is a link to my "surface map" of the floor I'm working on:
http://members.cox.net/timtritt/floor4.mht

Is a straight 10' 2x4 ok for a screed?

Thanks in advance!
Tim