2nd Opinion - subfloor for a hardwood floor

[duncanshannon]

Hi-

I'm ripping up carpet today getting ready for new hardwood (3/4" x 2 1/4" maple) floors in the master bedroom (at home) in about 2 weeks.

I appear to have 1/2"OSB and then 1/2" Particleboard sheets (looks like wood shavings / large sawdust and glue made into sheets...).  The guy at Lumber Liquidators said I need to rip up the particleboard and lay down new sheets of OSB or plywood because the nails wont stick in the particleboard very well.

Is that true?

Assuming it is, should I go with 1/4" or 1/2" as a new second layer? OSB should be sufficient right?

[PEG688]

It's highly unlikely you have 1/2" OSB sub-flooring   seeing they don't make 1/2" OSB.   It's made as  7/16" OSB , maybe it's swollen up to 1/2" , but still 1/2 " CDX  or 7/16" OSB  is NOT a normal sub floor sheathing  thickness.

  If you have forced air heat go around the house and pull a few heating grates and check in a few places.

  IF it's confirmed it is 7/16" / 1/2" OSB , yes you should glue and screw  down MINIMUM 5/8  satin ply / or 3/4" CDX / or 3/4" OSB over the existing/ Making sure the screws you use hit the floor joists meaning a 2 1/2" screw.

I'd use lots of construction adhesives between the sheet goods , the last thing you want is a squeaky floor.

ETA:  What you're looking for , mainly , out of this under-layment  is nail holding strenght, hence the thicknesses I recommended.   
Good luck, PEG.         

[duncanshannon]

Thanks PEG.

Yep, its 7/16 OSB. 

Its 1/2" particleboard on top of that.

So you'd agree to remove the 1/2 particle board then replace with 3/4 OSB (or ply).

Glue and screw the new 3/4 on top of the existing 7/16.

Bleh. Extra job scope that is no fun. I sure don't want it to squeak tho.

Thanks,
Duncan

[PEG688]

So you'd agree to remove the 1/2 particle board then replace with 3/4 OSB (or ply).

Glue and screw the new 3/4 on top of the existing 7/16.

  Yes, I added a bit to my last post about why. 

G/L PEG

[flyingvan]

  Have you considered this option?   On my first owner builder project, I had 3/4" subflooring down.  I bought a bunch of sheets of maple veneer plywood, and glued/screwed it down to that.  I biscuit joined the edges here and there and filled the screw holes.  The floor turned out beautiful and it's 9 years old now.  It was much cheaper per square foot too.  In your case I'd tear out the particle board first though

[duncanshannon]

Just to close this one out...

I put down 3/4" Sturdiboard (i think it was called) which was 4x8 TG and seemed to have one side that was more sanded and had any holes/imperfections smoothed out.  Guy at Menards upsold me pretty easily.

I glued and screwed - a no fun job that is for sure.  I hope it was a 'good enough' job.

Thanks for the advice and tips folks.

Duncan

[Don_P]

what you are describing is CDX plywood, the plugged, filled and touch sanded face was the "C" face, the open knotted face is the "D" face. It is glued with exterior glue to withstand construction wetting. For something like an exposed plywood soffit or a built in I'd probably look for AC Fir plywood, the "A" face is blemish free.

[Alan Gage]

what you are describing is CDX plywood, the plugged, filled and touch sanded face was the "C" face, the open knotted face is the "D" face. It is glued with exterior glue to withstand construction wetting.

Ahhh, so that's where the "X" in CDX comes from. Been wondering that lately.

Alan