On Apr 24, 7:52 am, DAC wrote:
On Apr 23, 9:47 pm, wrote:

Is there any reason why I wouldn't want to use either 1/4-inch lauan
or hardboard as underlayment for 3/4-inch oak flooring strips
(nailed)? The subfloor is 3/4-inch OSB with somewhat rough, uneven
surface and hardened glue in some places, which is why I want to put
down an underlayment to provide a more even surface for the finish
floor. I know I could use 1/4-inch plywood, but that is a little more
expensive than both the lauan and the hardboard. But if there's a good
reason not to use one or both then I will spend the extra money for
the plywood to ensure a solid installation. Also, what is the
recommended way of attaching 1/4-inch underlayment to the OSB
subfloor? I think the 7/8-inch staples I already have would be the
quickest - is that okay? Thanks!

At this moment, I'm installing 2-1/4 X 3/4 on 3/4 OSB and it too is
somewhat rough....meaning that there are slight differences from the
procuct and when the rain swamped the house when it was open. The
installation is going well, and it's extremely solid once down. I
don't believe you would be adding any benefit with the 1/4". It would
be smoother, but that's also 5/16 or so less staple or nail that hits
the sub floor. Also keep in mind that 1/4 will not mask any
inperfections with humps and bumps.

Rent belt sander from the renal store, and run it over the OSB knock
off the high spots like near the seams, don't use it on the glue
bumps, it melts into the belt (DAMHIKT). Take a sharp chisle and cut
the glue globs off. If it's too hard, add some heat from a heat gun,
it'll soften right up.

Good luck, I hope you have a strong back ;-)

DAC

You can also use a bondo sort of thing to bring up low spots and
smooth transitions. I'm not sure if its the same as concrete leveler
I used on my slab, but definately faster than a belt sander and helps
on low spots to keep it from sounding hollow or "springing" as you
walk over a low section and possibly causing nails to loosen and
squeaks to form.

Here's a trick - I made a large floor level out of a 12" rip of
plywood for the whole 8' length, drilled two holes in it and clamped a
4' level on top of it, also put a 18" Tee thing on the end to hold it
upright. That will show you where you need to work the subfloor.
Installing the actual flooring goes pretty fast, but the work to level
the floor is the most important and time consuming - at least on
concrete. I rated my floor job a 10 on a scale of 1-10 in terms of
difficulty, because my slab was not very level and had a high spot I
had to chisel or grind down - or buy about 40 bags of leveler to get
the rest up to that level ( and each bag is like $30).