what makes plywood "underlayment grade" ?

i was told here that underlayment grade plywood will be a significant expense in the overall installation of glue-down vinyl ...

to be honest i don't even understand why i need the underlayment ( i am working right now to find somebody who would remove the carpet so i can get a closer look at subfloor, without actually committing to installation - most of them only will remove the carpet if i also buy a new floor installation from them )

perhaps i could remove the carpet myself ? i just don't want to break my neck dragging it downstairs to the basement because the carpet is not really that old and i'm thinking of putting it to use in basement gym. could i do it myself ?

anyway assuming i need the underlayment 1/4" plywood what would make such plywood "underlayment grade" ? i recently bought some 1/4" plywood to make a box for my TV when moving - the plywood was fairly cheap and the TV was very well protected. i don't think it was "underlayment grade" ? but what does it mean anyway ?

 

i tried to research it and it seems it should also be extra moisture resistant ( compared at least to the subfloor OSB ) and made with harder wood to resist indentations.

but i don't see such products at Home Depot / Lowe's

i only see regular underlayment plywood not birch or anything cool like that ...

plywood is a fairly soft material when it comes to indentations ... it has strength in 2 out of 3 dimensions due to having fibers oriented in 2 dimensions out of 3 ... but this third dimensions is exactly the one in which it will be getting dented ...

it seems would be nice to at least have it out of some kind of hardwood ...

 

they seem to be out but i did find this page:

https://www.lowes.com/pd/SurePly-1-4-in-Whitewood-Plywood-Application-as-4-X-8/50124674

so $21 for 4 x 8 or $0.65 per sq ft. for 480 square feet that's $312. even if we allow for plenty of waste it will be $400. a far cry from $60,000 which somebody here said.

i really don't understand the "your bank account will tell you which grade to use" comment in this context.

that said, the above page says this is "softwood" so i presume there is a fair amount of room for the price to go up from here with better wood species, however i really doubt i would be able to find these underlayments or convince the installers to look for them.

i have already given up on "Natural Creations" in favor of "Vivero Best" because it will be much easier to find, much cheaper and almost the same thing.

i'm pretty sure i will similarly have to give up on optimum quality underlayment in favor of what can actually be practically obtained.

but i'm not seeing the cost of material as critical factor here. availability seems a bigger concern in this particular case.

in any case i don't see what's wrong with setting the goal high and then compromising as necessary to make things actually happen.

 

all right got it. perhaps go with something like this:

Underlayment (Common: 7/32 in. x 4 ft. x 8 ft.; Actual: 0.196 in. x 48 in. x 96 in.)-431178 - The Home Depot

question - is there a chance there may already be such underlayment under the carpet ?

i had no luck getting anybody to remove the carpet for a cheap price ...

should i try to look under it myself at least ?

or just try to negotiate flooring installation price that is contingent on subfloor condition ? like i want them to install the floor the right way but the price will depend on what's actually under that carpet once they remove it ...

is it possible to get an estimate with provisions like that ?

or have them come and lift up some of the carpet, look underneath and give estimate based on that ?

how to proceeed basically ...

 

thanks !

 

well believe it or not i had carpet removed yesterday !

the guy who did it is also painting the walls today.

he's not a flooring pro - more like a jack of all trades type.

anyway that OSB looks HORRIBLE ! for some reason it looks a lot worse from the top than it does from the bottom side from the basement.

the floor itself seems level but the gaps are about 1/8 inch and the corners of many panels are chipped and there are also some random strands here and there that either stick out or crater. some screw heads are not flush and so on.

i'm sure it can all be fixed but once i saw the floor i instantly knew what underlayment is for.