7/16" subfloor in my house?!?!?

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latelifebiker

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Why would the builder of my recently purchased, early '80s house put down 7/16" plywood over the floor joists, then build the partition walls on top of it, and THEN put down 3/4" plywood as underlayment BETWEEN the partition walls? I would have most assuredly put the 3/4 down as the subfloor.
In the kitchen he glued linoleum directly to the top of the 3/4" ply, so I have to cut it out in order to lay a new floor. In a way, it's a blessing because it gives me an excuse to install 23/32" AdvanTech over the tissue paper subfloor and to be sure it's fastened properly.
In the rest of the house, where he installed carpeting, he used 3/4" particle board as the underlayment, and that gave us a structure in which 80% of the floor structure consisted of 7/16" plywood and 3/4" particle board. Again, to my good fortune, they had small pets that ruined the particle board, and I could tear it all out and install 23/32" AdvanTech before laying 3/4" solid oak planks. Can you imagine the difference underfoot?
 
Your house likely failed framing inspection when it was built and the 3/4 was required to fix the problem. The inspection would have been done after the whole house was framed. Adding adventech is a good solution. For best results screw to the floor joists every 6" and with shorter screw in the middle to suck the plywood up to the adventech. Run the adventech in the same direction as the plywood and have the end joints land on a joist but don't put one joint on top of the joint under it.
 
But, Neal, would an inspector allow the builder to get away with 3/4" particle board over the 7/16" plywood in the 80% of the house that would get carpeting?
This is the third house I've owned in this county (Cobb County, GA) that was built in the late 70s or early 80s, and I'm convinced that in those days the county's building inspectors were for sale to any contractor with a few bucks. In ALL THREE houses, whenever I wanted to do a repair or renovation, I would have to back into the project by doing two or three fixits to make the actual, intended repair sound and solid.
 
We see alot of K3 board in older houses, maybe it wasn't against code then. I've seen pre-cut stair treads still at HD out of K3.
 
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