Underlayment advice for oak flooring strips

[mj2736]

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!

[scott]

Perhaps a floor installer will chime in, but in the mean time, I have glued bamboo to the floor in my slab house. Floor leveler is recomended even for wood subfloors I belive to even out joints, low spots, etc.. I would not go to the trouble and expense of using lauan or hardboard, in fact I doubt you would get near the nail retention you would just with the OSB.

found these pages on a quick search, you can do the same :!)

[TVeblen]

Save your money. 1/4" anything will not add any appreciable strength to the floor unless you glued and screwed it in place to achieve a complete bond across the entire surface. Staples would be the worst fastener to use, followed closely by overdriven gun nails. The plywood will span lumps worse than 3/4" flooring strips. Your chances of floor squeaks will increase significantly. And the normal staples used to install the strip flooring will perform worse through the 1/4" material. Get out a hammer and wide chisel and knock off the glue and any other glop on the floor. Drive down any proud nail heads. Chisel down any swelled joints. Use a thick underlayment paper like heavy felt. And run the flooring perpendicular to the floor joists regardless of any aesthetic considerations. The hardwood floor manufacturers association has never recommended installing hardwood strip floor over OSB plywood due to poor fastener grip. The engineered products like Adventec are approved, but not true OSB plywood. But this defect could be overcome by using extra fasteners.

[marson]

For a nail down hardwood strip floor, I don't see the value in adding underlayment. Even out your existing subfloor as best you can with a scraper and belt sander and go with that. Many, many old houses have hardwood strip floors put down over very nasty shiplap, and these floors are fine. Use 30 pound felt as an underlayment to pad the irregularities.

[steve robinson]

Make sure that the underlayment paper is not bituminuim based , in hot areas its been known to stick the floors together , the floors need to have an expansion facility thats independant of each other

[<marierdj]

I can see the merit of nailing hardwood floors. However I question the fact that in most cases the nails are driven into a 5/8 - 3/4" thick plywood. The quality of the plywood floor is not always No. 1. Not to mention the expansion of the 3/4" thick hardwood would it be acceptable to glue the hardwood strip instead of nailing. The other thing I was thinking about would be to pre - drill and screw the hardwood. Here again the holding power of a screw driven into plywood in not all that great. What do you thing.

[DAC]

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

[steve robinson]

hardwood floors should never be glued to a timber sub floor

[Joe]

Wouldn't it be a whole lot easier to just pull up the crumble board and put down some decent plywood? The nail holding power would improve a bunch and the subfloor (with care) could be dead level. Door bottoms would not have to be shortened and there may be other advantages as well, like no squeaks, less bounce, etc. Just wondering...

Joe

[scott]

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).