Greetings.

I've been on the forums a while and I have read the "OSB or Plywood" sticky. And yet...I still have to ask OSB related questions.

My house is about 18 years old. The joists are engineered i-beams (Weyerhauser SilentFloor 150 grade)...on 19.2 centers. The subfloor is a single layer of 23/32 OSB, T&G, PS2-92 spec. Where there's carpet, the carpet pad is directly on the OSB. Vinyl areas have 3/8 ply underlayment.

I'm looking to put hardwood in much of the house (somewhere between 1200-1700 sqft, some areas are still under consideration. The motivation is we need to do _something_ - after 18 years with cats in the house, the carpet is due for replacement. Plus we have some allergies that are being triggered by carpet (dust mites). I really don't want a laminate floor (at least not floating) over much of the house.

Every option for working with my subfloor seems undesirable...

1: Use as is - I know nails/staples don't work as well with OSB. I was planning on using 2" staples making sure to hit the joists. My subfloor complies with NWFA...Still...OSB concerns me.

2: Laying ply over the OSB. I could possibly live with 3/8 ply...but I'd rather not.

3: Replace the OSB with ply. Probably the best bet from a flooring quality perspective. I don't relish the thought.

One of the rooms with vinyl is the master bath...and I'm planning to tile that later after the flooring and kitchen work is done.

So....what should I do about my sub? :\

Laying a new floor over OSB is not a problem. Staples will hold better than cleats.Go across the floor joists. Nailing into the joists may help, but is not a requirement for a good floor. If you want a tighter, more secure floor then use narrow strips which will give you more fasteners per square foot.
Adding another layer of plywood will add the possibility that this material will not be fastened securely to the sub-floor, and you will get less penetration into the OSB with your florin g fasteners. Essentially, you will be re-fastening the 3/8th to the OSB as the fasteners go through the plywood, unless you glue the plywood to the OSB with full coverage. This is a lot of work that I think is unnecessary.
Try fastening a couple of rows of flooring and then try to pull it up with a 6 inch nailing schedule instead of 8-10 inches. Fasteners are inexpensive, use more if you think that they don't hold good enough, or as well as into plywood.

Great. Thanks, Pete!

For the record, I maintain pretty consistent indoor conditions. Temperature is pretty much always in the 64-74 F range. Rarely will I let it drop to 60 or below. I'll be using a moisture meter prior to install.

The only boards I'm not planning on running perpendicular to the joists will be door threshhold borders and perhaps around the fireplace assuming I continue laying hardwood out to the living room.

Your point about the added plywood not helping is well taken - one of the flooring stores I've visited tried to insist that I must be mistaken and that I have 2 layers of OSB. I'm quite certain it's one.

The unknowns yet are exactly what condition the subfloor is in (smoothness, etc). I'm concerned about one spot in particular but that's in the back of a closet. Our house sitter locked a cat in the bedroom accidentally while we were on vacation and the closet became an impromptu litter box. The carpet was pulled 10+ years ago and replaced with laminate, but I'm guessing when the laminate comes up, the subfloor has continued to degrade... I believe the rest of the subfloor is fine.

Thanks again!

Water will damage wood, and the chemicals from urine will stain it , but as soon as it dries there will not be any rotting.
Framing with the engineered joists should be pretty smooth, if the OSB did not get damaged from weather during installation. Sometimes the butt-joints and edges of panels will swell from standing water and can be sanded down with 16 grit discs on an edger, which will not bother the strength. The closet may have been wet for some time after the cat was rescued and swelled up some, too.

My update:

Finally bought (and received) some flooring - it's acclimating now. Got a deal I couldn't ignore on some Anderson oak.

I think my OSB is in good shape. I loaded up the stapler I bought with some Bostitch 2" 15.5ga staples and set my compressor at 75# for a first test on a 'short' Damn near perfect. I'd like to see about 1/32 more depth than that (fired between joists, not into a joist). Took quite some effort to remove.

Only 2 things I'm (particularly) unhappy with about my OSB (besides it being OSB)...

1: Looks like the trades just set off texture mud grenades inside my house when it was being built. It's splattered all over the floor.

2: They left...no joke...a hole in my subfloor. Not huge, about the size of a $.50 piece. In its location, it really can't be seen from the basement. I'm probably going to fix that tomorrow (with a frame made from 2x2 nailed to my joists and a piece of ply on top).


T