[mgmine]

Same reason they use steel bathtubs instead of cast iron, $$$$$

 

[mgmine]

OSB is cheap and that is why builders use it on other people's homes. It doesn't hold nails very well, it swells up when wet and doesn't have the strength of plywood. Why skimp on materials? I have seen builders actually use plywood and pressure-treated wood for foundation basement walls. I have also seen them put steel bathtubs in $300,000 houses.

 

[mgmine]

I wish I had taken pictures of the floor I put down in a cabin in Canada. It was about 20 years ago and I was replacing a floor that was put in 50 years prior to that. The original sub floor was solid pine that I replaced with 3/4" OSB. The original sub floor was about 6" off the dirt ground. I hand dug the dirt to a depth of 4 feet thinking that would be fine. I was wrong within a few years mold started growing on the OSB and 10 years later the floor was completely rotted and had to be replaced again. The original floor that was still in place in the front of the cabin is still as solid as the day it was put down in 1939. That part of the floor had an air space of at least 3 feet. So air space caused the original floor to rot but even with 4 feet of air space the cheap OSB rotted.