On Friday, December 1, 2017 at 11:23:39 PM UTC-5, wrote:
On Fri, 1 Dec 2017 22:00:56 -0600, Terry Coombs
wrote:

On 12/1/2017 9:01 PM, Uncle Monster wrote:
On Friday, December 1, 2017 at 8:44:53 PM UTC-6, wrote:
I dont know if anyone actually discusses home repair on this group
since it's mostly all politics now, but if anyone happens to still
discuss the intended topic, I am looking for some advice about
replacing the floor around my toilet. The floor was made of particle
board and it's gotten bad. I need to replace it around the toilet. The
toilet is loose and has been a little crooked for a long time now.

I know how to remove the toilet, but I am not sure how to fit the
floor around the flange. I plan to use treated 3/4" plywood for the
replacement. The problem is that I have always seen the flange sits ON
TOP of the floor. The plumbing is PVC so I assume the flange is glued
to the pipe. I know that can not be separated.

So, how do I get the flange ON TOP of the floor? The only thing I can
think, is to install it in halves and shove it under the flange. I
suppose this would work, but I'd like to avoid having a seam in the
plywood right under the toilet, especially since I cant add some 2x4
framing under it, with the flange in the middle.

Is there another way to do this?
It appears that you have it figured out but you should use treated 2X4 lumber
under the treated plywood halves. Something to seal the seam and any gaps in
the repair might also be a good idea. ^_^

[8~{} Uncle Toilet Monster

Â* He'd be better off to use pieces of the plywood under the joints .
Screw some ledger boards to the floor joists to hold the pieces up(flush
with the top edge of the joists) , effectively doubling the thickness
under the toilet . Construction adhesive is your friend . And don't
forget to screw the flange down to the new subfloor . (20 years as a
flooring installer , did my own subfloor repairs 'cuz the carpenters
just didn't understand what was needed .)

Â* --

Â* Snag

Thats a good idea. This is a trailer house and the floors are nothing
but 3/4" particle board. No sub floor. Since I will have to replace the
vinyl, I was going to cover the whole room with 1/4" treated plywood,
but it appears they dont sell 1/4" plywoods in TREATED. Bathroom floors
are always getting wet, so I think everything should be treated. I
suppose I could put 1/2" treated plywood down over the top, but it will
then be a lot higher than the hallway by the door, and also around the
tub. (No, I'm not removing the tub). I suppose the extra 1/2" really
would not matter that much around the tub though.

Either way, after I install new vinyl, I plan to put silicone around the
walls, tub, and toilet so water can not get under.
Yes, I know to screw the flange to floor.

Whoever decided to use particle board for floors should be shot!

I agree with the other good advice, the ideas you've been given
and your plan.
But I would not bother with siliconing around the edges, that's overkill.
I'd look into why the existing floor failed. It typically takes either
water that keeps wood constantly wet for a long time or insects to make
a floor fail. The former generally comes from leaks, not someone getting
the floor wet from stepping out of the shower, etc.