I know one downside to OSB is in a horizontal application, it doesn't do well if it gets wet for too long. I have to wonder if a spongy floor sometimes could be due to a water leak. Personally, I hate OSB. It's heavy, it smells awful and it gives you awful slivers. I assume the smell is formaldehyde off-gassing.
I wonder what spans they typically use for floor joists in TTs? If they are using 24" centers, by building code standards I just looked up, the OSB would have to be 23/32" or 3/4" thick T&G. For 16" centers, it should be 5/8". Do they ever use 16" centers? I really have to wonder if OSB that use sometimes is just too thin for the joist spacing? I sure can't see them using 3/4" OSB in a TT esp. if they call it an ultra-lite.
Are you sure OSB is rated for a higher load? It's been a while since I've been involved with the building code aspects but this is from a plywood manufacturer:
Plywood is a highly stable panel. When exposed to moisture or high humidity,plywood is up to seven times more resistant to thickness swell than substitute wood-based (OSB) panels. Plywood also returns to its original dimensions when it dries. Plywood is stronger than substitute wood-based panels in the four important engineering strength properties of bending, tension, compression and planar shear and plywood weighs up to 40% less than substitute wood-based panels of equivalent thickness. Plywood is a highly impact-resistant panel and continues to perform even when wet. I wonder if different grades of plywood are used in different regions of the US & Canada? We get a lot of rain around here and I know it's the choice of structural engineers (at least in BC).
Our house is 100% plywood because I designed & built it myself. :) OSB is really common on spec houses and townhouses but rainscreen assemblies are now required on exterior walls which is something that came out of the leaky condo crisis of the 80s.
westend wrote:
myredracer wrote:
Some sub-floors are OSB and some are plywood. I would expect more potential trouble with OSB. Our TT has plywood which is one of the reasons we bought it. I wouldn't buy one with OSB.
I'm not really sure what exactly defines "ultra-lite". I think it's more of a marketing ploy to suck people into thinking their TV can handle the weight.
It's not always about a single material subfloor. Some mfgs. use a composite structure of luan or cheap plywood and foam. Although this type of sandwich construction has a lot of strength along it's shear face axis, it is hard to get real strength through the composite core axis. I would venture that the "spongy floor" complaints happen in high traffic areas, around the entry or in front of the sink cabinet.
FWIW, if your S&B house or apartment was built in the last 20 years, you'll probably find OSB is under your feet. OSB is rated at higher load and water resistance than interior plywood. Mostly true for roof sheathing, as well but depends on geography for that.
