A spongy floor around the toilet is a strong indication that the subfloor has absorbed water.
Floor under a toilet.
Access a crawl space or basement and locate the plumbing drain below the toilet.
A toilet would actually never leak right onto the floor.
The toilet has to be removed and the flooring cut to go around the floor drain.
Because laminate flooring floats above the sub floor on top of underlayment it will expand and contract slightly with the temperature and humidity of the room.
Then i leave a gap of 1 4 or so to the rest of the flooring that will be.
On the walls ceiling and the floor.
Peel the flooring several inches beyond the rotted area.
If there is any leaking that occurs in a toilet it would happen through the floor and not on the floor.
Put on safety glasses and work gloves.
Then the toilet is reset so the base covers the cuts around the drain.
So what i am thinking is i basically cut a round or square i guess now that i think about it piece to go under the flange.
Enough to create two square frames to fit between the floor joists and under the cuts.
When choosing bathroom flooring consider how it will perform under stress and the stress event in this case involves water lots of it.
Clean the flange well or use a new one and install over the drain and new wood.
Repair floor under toilet nail the plywood to the floor joists.
Toilets tend to leak below typically into a basement and seeing cases where a toilet is actually leaking on to the floor is quite rare.
Make sure to make your nails flush with the wood.
Toilet drains are 3 or 4 inch in diameter and have a p trap below the toilet.
It goes under the flange and transfers the load of the flange and toilet and you out onto more solid surrounding wood.
If only the area directly below the flange is rotted you can install a two piece steel closet flange support.
Am installing some allure vinyl floating floor in bathroom i am also installing a new toilet flange and toilet since i replaced the subfloor there.
Water is so prevalent in bathrooms that it is an expectation not an anomaly.
If you re installing a new floor pedestal sink and toilet you should install the laminate flooring first so it s under the sink and toilet.
You may need to scrape the flange with a small putty knife and use a wire brush to get it clean and free of any corrosion or debris.