Normally your shower and anything else in your bathroom is supported by the wood joists inside the subfloor. If the joists are weakened by leaking water and you do nothing about the problem, the shower may eventually fall into the room below. Knowing the warning signs of a water leak helps you repair the situation before it becomes dangerous.
Shower Leak Detection
You need to always watch for any signs of your shower leaking, since a leak that goes unnoticed can do significant damage to your house. A shower's leak may at first be contained to the subfloor only, but you may notice that the floor around your shower is spongy or it flexes more than the rest of the floor, indicating possible water damage. Water dripping from the ceiling below the shower, or water stains on the ceiling's paint, may also indicate a leak coming from the shower. Also, if the paint on the ceiling starts to bubble or peel off the drywall, moisture can be present.
When structural wood in your house is exposed to high levels of moisture, that wood can begin to rot. Even though the leak coming from your shower does not allow much water into the subfloor, it may be enough to beginning rotting the floor joists. If the floor joists rot enough, they can suddenly give way, causing the shower and anyone in it to fall into the room below. If you suspect the floor joists are rotting, you must examine the joists either by tearing the bathroom floor or the ceiling in the room below. If the wood has not begun breaking apart, stopping the shower leak will cause the joists to dry out and regain their strength.
Leaks coming from the shower can also promote mold growth in the subfloor. If left unchecked, the mold growth can also break down the floor joists, weakening them to the point the bathroom floor can give way. As with wood rot, you must expose the subfloor to confirm that mold growth is present. If you find mold, you must scrub it off with a nonammonia-based cleaner and clean all of the surfaces with a mixture of bleach and water. If the joists still have mold on them, you can sand off the mold growth.
Finding the Leak’s Source
Once you know that your shower is leaking, you must determine if the leak is coming from the faucet, the drain or somewhere inside the shower. To test the faucet and water supply pipes, have one person watch the area where the leak is manifesting itself while someone else fills a large container with water using the shower faucet. If the leak appears, then you know the faucet is the source. If the leak does not start up again, pour the water carefully only down the drain. Spray different areas of the shower with water if the drain does not produce the leak, pinpointing the source of the leak. You may need to chisel out grout and apply a fresh coating or apply bathroom silicone caulk to leaks inside the shower.