concreteflooring
I'm looking to remove my basement carpet and replace with a floating floor. Not sure if I need to scrap up this glue when I will be laying a 6 mil vapor barrier over the concrete anyways. The black part in the picture is where I tried scraping some of the glue.
Tool rental places probably rent concrete grinders for big jobs like refinishing concrete floors and then you can use a sander that get get into corners.
Floor Grinder
Concrete Sander
You can probably rent one or both of these, depending on the amount of glue. If it's just spotty you can probably use the hand sander.
Like I said, these are for professionally prepare floors for concrete finishing. If it is thin you might try belt sander or palm sander, and buy a sampling of sand papers and see which works best.
Belt Sander
Palm Sander
If you choose to use plywood, go with the 3/4" T&G for the layer under the carpet. The trough were the heat pipes used to be can be spanned by the 3/4" plywood too. Also since the carpet compresses under foot, keep the plywood below the hardwood layer about 3/8" or so lower. That way when you step there, the transition will feel level.
Best Answer
if you follow the directions for the new flooring, the answer would be yes, to scrape it all up. here's the thing, when doing floating flooring, the floor underneath needs to be smooth, or you could feel imperfections through the floor as you walk. now that being said, as long as there are no big ridges in the glue and its all smooth, you should be able to get away without removing it. make sure that you remove all of the old tack strips and nails, getting the subfloor/concrete as smooth as you can before you install the new flooring.
I put in laminate flooring with attached underlayment back in april. There were a couple of spots on my subfloor that were not 100% even, joints in that were off by 1/4" and I was able to leave them, and now you cant even tell they are there.