Hey there,

I'm hoping someone might be able to help me sort out my confusion regarding my impending floor installation. Here goes:

I'm poised to install a floating bamboo floor, but my subfloor is all over the map as far as level / flat is concerned. I've got 15# and 30# roofing felt, but I'm going to need loads of it to get the whole floor prepared. Is this normal to go through LOTS of rolls of felt to get the floor prepped? Or should I shim the really low spots with plywood / masonite to get a roughly even elevation and then go for the felt? (Sags up to an inch at some edges.)

Is there another way to prepare a really weird subfloor for a floating application other than shimming? I think I read on this forum somewhere that one wouldn't want to use any cement floor levelers or anything...I feel like I need sand, or some other miracle-leveler.

Also, can I get away with just the 15# felt (after leveling) as the underlayment or will I need something squishier? (Am using 6mil poly in the crawlspace for moisture barrier)

Thanks in advance for any light you can shed on this for me!

Dave T.

With a floating floor, the perimeter of the room never gets walked on. Heavy furniture is the problem in those areas, and should be a concern.

When doing floor prep for a client, I will deal with them and flatten them out.

If it were my own home, I'd get it close and call it good.

My concern would be out in the room, where foot traffic is going to be.

Flexing the floor from foot traffic is what is going to make your installation fail, not along the walls, unless it is extreme and extending out more then a foot from the wall.

Try to knock the top off the high spot, before filling the low spots.

Sounds like your floor joists are placed to far apart. Measure them. You may need to fix that. Flexing of the floor is going to ruin the locking mechanism or glue bond of the Bamboo joints.

hi Floorguy,

My concrete has a noticible raise 2 feet from the wall/fireplace.
How do I "knock the top off the high spot"?

thanks,
rob

Grind it down with a floor grinder, with dust containment.