How clean does the subfloor need to be to install a new floating floor?

[Matt Lentzner]

Not exactly woodworking, but...

I am replacing the floor in a half bath with a floating engineered floor. The original flooring was linoleum (or something similar) glued to the slab foundation. I pulled it all up, but in several places the skin separated from the paper backing which is well glued to the concrete.

It has been slow going trying to scrape that paper off, and I'd like to know how to speed up the process. I tried using my ROS with 80 grit and all I did was make the paper very smooth. (I'm an idiot; I know)

I though maybe a belt sander with a very low grit would do the trick, or maybe a paddle grinder. Those both could be messy. I believe there's also a giant two-handed scraper that the pro's use. Lastly, I could just leave it and figure that with the floating floor and underlayment it won't make a difference.

Thanks for your help,

Matt

[Sean Kinn]

How high are the high spots? Depending on the foam backing or underlayment it likely won't matter at all. Just lay out a piece or two of the new floor and see how flat it lays over the rough spots. Stand on it and see if it seems to "teeter-totter" on the high spots. Biggest problem I had were low spots in my floor that I hadn't noticed until the new floor was installed. Now I can just barely perceive the floating floor flex while I step on the flooring over the low spot.

[Matt Lentzner]

The high spots are the height of maybe two or three sheets of construction paper although it's not just a spot here and there. There is paper stuck in a 2' x 2' area around where the toilet was.

Matt

[frank shic]

matt, get one of those scrapers that have a LONG handle from home depot's and scrape away until you feel at better ease although it sounds like it's a fairly thin amount of material that will just get covered up by the underlayment foam. when i installed my laminate floors three years ago, i insisted on yanking out EVERY SINGLE staple or stray nail that was in the subfloor. now that i'm a little wiser i just whack them down with a hammer so they don't interfere with the flooring underlayment whether it be backerboard or something else.

[Tim Morton]

maybe some "floor leveler"...a skim coat should do.....

[Larry Rasmussen]

already be flat enough. I got really obsessive about our small kitchen but after several longs sessions of scraping I just left some of the glued on paper. Take a good look at that pad or even cut it and put it down. It will be nice to have it done ahead you can see if you can see or feel anything in your paper spots. Larry.

[Greg Dykes]

Matt, I do flooring for a living. You need to read the specs. for the brand of engineered flooring you have. Most only allow for 3/32" deflection over 4'. Even after you get (if you get) all the old material off the floor, you need to check if there are any high/low spots in the floor. Bathrooms are noted for not being level due to the concrete having to be worked around pipes sticking up while it was poured.

Best solution, floor leveler and a flat trowel. If the floor is not flat/level you will have squeaks and premature failure of the joints.
Good luck!

[Matt Meiser]

Heck, an OSB floor is less flat than a few sheets of construction paper. That foam pad is pretty thick relative to that.