I have a 3/4" OSB (straight edge 4' x 8' sheets) subfloor directly over 1.5" x 9.25" pine joists on (give or take) 16" centers with a span of 13' 4".

The OSB is about 30 years old, in decent shape, is fastened to the joists with ring-shank nails, I doubt it's glued and (although it feels sturdy) pops and snaps a bit in places when I walk on it.

I plan on pulling carpet and fastening the OSB to the joists with a few lbs' of galvanized deck screws which leads to my question:

Will a 3/4" x 4" hardwood floor nailed to and through the 3/4" OSB work well..... or..... should I oughta' consider laying another 1/2" of ply over this 3/4" OSB first?

Or should I consider a thinner hardwood.... or an' inguneered' product like a floating floor or some other product.... or some kinda' special fasteners?

Mostly..... will nailing to 3/4" OSB subfloor work well.... and last well?

Thanks

Hey Dave,

I doubt your subfloor is OSB. Either that or your house isn't 30 yrs. old. Pretty easy to determine the age of the home. It should be listed with the real estate docs you got when you bought the home. OSB wasn't used much prior to 1990. You sure it isn't a type of particle board? Can you post some photos of your subflooring? The reason I say this is true OSB is an approved subflooring for nailing hardwood to. Particle board is not. So, to decide whether or not you need more plywood, we must first determine exactly what your subfloor is made of.

The subfloor is 3/4" OSB.

My concern is.... will a 3/4" or 1/2" hardwood floor nailed to the OSB substrate be a good thing.... and will it last.

I have heard of new, coated fastener types that may enhance hardwood connectivity to OSB... but I am not sure how to rate and differentiate them.

Is 15" roofing felt directly over the subfloor recommend in my situation?
What kind (make & length) of fasteners would be best in my situation?

Thanks folks.

First like Gary said about OSB. OSB what not used for subfloor 30years ago. We are just trying to help here. We just need a pic or two to come up with the question. If it is 3/4" PLYWOOD way should you add more on top of it? That is just more weight on the joists.
Jeff

good luck

I remember seeing OSB show up here about 1995.

1989 was the first time I saw it in a home. Either his home is newer ( not 30 years old ) OR, his subfloor isn't OSB. It could be the earlier version called "wafer board or flake board". NOFMA and the NWFA do not recommend installing directly to, or over, any wood subfloor other than solid wood planking, subfloor rated plywood or subfloor rated true OSB. There were composite subfloor panels made 30 years ago and perhaps this is what the OP has. An earlier form of wafer board. Regardless, if it isn't plywood or solid wood planking, it would be prudent to overlay with more plywood, 3/8" minimum, stapled or nailed and glued or screwed.

http://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr53.pdf

Thanks Jeff, "AF" and Gary.

History of Oriented Strand Board

Evolving from waferboard in the late 1970s, OSB is unique in that long wood strands are oriented, not randomly placed. Since its debut in 1978, OSB has been rapidly accepted. In fact, in many areas of North America, OSB has virtually replaced other panels in new residential construction. Today, all model building codes in the U.S. and Canada recognize OSB panels for the same uses as plywood on a thickness-by-thickness basis.

For general building and structural panels, OSB is usually fine. Keep in mind, for subflooring that one wants to nail a wood floor down to, the NOFMA minimum requirement is a 5/8" plywood subfloor OR and 3/4" OSB subfloor. So, there isn't a plywood equivelant in OSB for 5/8" plywood subflooring. One would just use the 3/4" OSB. Virginia Tech did a study of the various products and fasteners. Solid wood planking held fasteners best, followed by 3/4" plywood with 5/8" plywood and 3/4" OSB having similar results. Staples worked best in the OSB subfloors and held better than cleats.