I have a small bath just off the master bedroom that I just remodeled last spring. This was a complete gut and redo from the floor up.

I removed the tile and the sub floor, replaced it along with removing the fiberglas tub and all the dry wall.
All fixtures were replaced with new, we installed a pedelstal sink, new toilet and an old cast iron tub. I had a plumber come to do all the plumbing.

This bath sits over my garage so I can see the plumbing coming from all three fixtures. There are no leaks and there are goose neck traps for the tub and the prdelstal sink. No leaks of any kind under the bathroom around the plumbing.

I personmally set the toilet myself and installed a new "thick" wax ring.( I did not calk around the bottom of the toilet to the floor. There are no leaks around the toilet or the tub and sink.
Inside the wall, the vent was not disturbed while I had the drywall out. The vent goes through the roof and does not terminate in the attic.

We have been using this bath all summer with no issues but it jut started smelling and it takes over the bedroom and into the hall. I have ran water to ensure there was water in the trap on each device but it is still there.
Oddly, on the other side of the wall behind the toilet and sink is the master bath, There is absolutely no sign of odor in that bathroom. The vent is my next thing to check, I will get on the roof tomorrow but I was thinking it should smell in the other bath if it was clogged.

I cannot for the life of me figure out where this is coming from. Everything is new, Installed correctly and nothing is leaking. Everything drains fine. I also am on a septic tank but there are no problems with it. I had it pumped about three years ago, it is an 1100 gal tank and there are only two adults living here so it shouldn't need to be pumped again

Can anyone help?

I'm willing to bet that wax ring on the toilet didn't seal properly.

I agree with Smoothy. I would pull and reset the toilet and then caulk around the base of the bowl for added protection. Good luck, Tom

Thanks to you both
I will do that and follow up if it fixed it

Well I removed the toilet and the wax ring top did not appear to have had anything more than slight contact with the toilet so I thought that was it.
I replaced the ring with a thicker one and I know it is sealed now.

The smell is still there but not quite as strong. It comes and goes, one day it is bad and another it is not there at all

I looked again under the toilet drain in the garage and everything there is fine. I did however; get a bad smell from the garage the night I decided to remove the toilet but again, I saw absolutely nothing that would cause the smell. I ran my hand along all the PVC and there was no hint of wetness or anything loose

I am stumped

Well I removed the toilet and the wax ring top did not appear to have had anything more than slight contact with the toilet so I thought that was it.
I replaced the ring with a thicker one and I know it is sealed now.

The smell is still there but not quite as strong. It comes and goes, one day it is bad and another it is not there at all

I looked again under the toilet drain in the garage and everything there is fine. I did however; get a bad smell from the garage the night I decided to remove the toilet but again, I saw absolutely nothing that would cause the smell. I ran my hand along all the PVC and there was no hint of wetness or anything loose

I am stumped