The Shower Floor Feels Squishy

Not to mention i have to battle mildew growing on parts of the grout even though we wipe down the shower after every use and leave the fan on.
The shower floor feels squishy. If the floor deflects a 1 2 of an inch there may be a concern. I just bought the house 4 months ago. I cannot see it with my eyes its that shallow. If left unattended eventually the entire flooring system under the bathroom will collapse.
As an aside the caulking where the shower tub meets the floor looks like it needs to be replaced which is on the to do list but we don t shower in this bathroom and the tile that is squishy isn t next to this area. If this material is subject to moisture or hidden leaks the plywood will rot and the floor will start to feel soft or spongy in places. Basically undersized floor joists or trusses or spacing too far apart may lead to sponginess. This condition allows the floor to give slightly when you step.
But i can feel it with the ball of my foot or my hand. If there s a crawl space under the house you could brace it from underneath but that s not the right thing to do. Your toilet may also feel unstable rocking when you sit down. If the sub floor is not strong enough to span the distance between the floor joist trusses or supporting beams then sponginess may occur.
Thank you for any help. If you are accustomed to a tiled shower base you will immediately sense the difference. The master bathroom has a tile shower. I ve noticed a soft spot on the tub floor about 3 round.
Sub floor undersized or engineered. Does the floor feel soft or squishy. Types of bathtubs that commonly have this problem. No jets so no access panel.
After the shower is used and the floor has dried stepping on some of the tiles results in a squish noise and a little water comes up through the grout. Does your bathtub or shower have a crack in the floor. Best is to remove the tub shower unit rip out and throw away the rotted. Normal amount of flex few prefabricated shower pans will feel as rock solid as a tiled shower base.
Some bathtubs commonly develop soft spongy floors over time that lead to cracking and sometimes will cause leaks underneath the bathtub. There are no visible cracks and no water damage to the floor underneath it s over a second bathroom. Fiberglass bathtubs cultured marble tubs plastic bathtubs etc. A spongy feel underfoot might indicate that the subfloor is not securely attached to the floor joists.