First off, what a great resource this site is. Great job for all those who’ve contributed to this site.

I've just purchase an "executive" (whatever that means) 3300 sq ft home. The home was affordable because nothing upgraded inside since it was built. The home was built in 1991. I forgot to look at the subfloor during my home inspection but my Home inspector says its chipboard. Mind you I don't recall him taking anytime to verify, I think he's just presuming.

First question: Were they using chipboard during the period this was built (1991) for a subfloor. Or is it most likely OSB or other? As I understand there is a difference. One is randomly sized & sorted and the other is specifically sized and sorted for optimal strength. If it helps the home is in the greater Toronto Area in Ontario.

Due to my obsessive nature I've talked to every retailer/installer on the east side of Toronto. The smaller "independent operations" all of whom they claim 20 years of experience say they can lay it right on the existing subfloor as long as it is flat, smooth and screwed down, then install the hardwood floor with staples. The larger chain-like stores with younger installers / sales staff, suggest that at least 3/8 ply should be installed over the subfloor.

Second question: I have one week with the house empty, time and cost is a factor. If I listen to the majority of advice that I received then I would install it without the added plywood. I suspect it’s an “old timer” vs. "new school" debate. Old timers think I'm just wasting my money. While younger whipper-snappers say I could be in trouble. One hardwood manufacturer recommends putting two staples in a small piece of flooring (i.e 12”) and if it can be pulled off by hand then the subfloor is not suitable. Here's the question, should I try the test as I just mentioned, or regardless install the 3/8 ply on top.

Whew, sorry for the lengthy email... hopefully it doesn't discourage anyone from reading!

Thanks

Its probably OSB... but thats about the time frame alot of builders were using 5/8... which is no good anyway unless you add more plywood. You need to determine what is is, how thick and the OC joist spacing.

Joint spacing is close, I never actually measured but I know it is not greater than 16".