Bathtub Floor Damage
This bathroom floor damage was
probably caused by moisture rolling off of the bathtub and down the
corner, onto the floor. This damage is less than 4 inches square and
won't be that difficult to repair.
Here's where the problem could become a nightmare. This is the only visible damage that we see and it will not take much effort to repair it. However, we don't know for a fact, what caused the damage.
We're assuming that, the water rolled off of the bathtub and eventually ruined the sub floor while we were using the bath tub or shower. But if you look closely, you can see that someone has applied caulking between the bath tub and the tile, in the corner.
Did this solve the problem or is it now holding the moisture behind the tile? It's hard to know for sure, without doing some forensics or removing the bathtub or tile bath tub surround.
These are the problems that most homeowners seem to miss. Examine the tile for any hairline cracks, small holes or other damage, before assuming that your problem is solved. Make sure that you look for hairline cracks in the grout.
I've seen these hairline cracks do a lot of damage to the bathroom and the ceilings below.
Home Repair Tip - Repair this area of the floor, install your new flooring and then, I would strongly suggest, that that you continually examine this area for moisture. If the flooring becomes wet in the corner, try to find out if it's an external problem, like the shower curtain or someone splashing around in the bathtub.
If it's an internal problem, finances will usually dictate the results. If you don't have the money to repair it now, you could be repairing the framing to the floor later. But money, talks doesn't it.