shower stall with hole (cold air coming in)

mcvane

We have a shower stall in our basement washroom. We moved in about a year ago, and it was not a very 'clean' looking job.

I cleaned out all the silicone in this shower stall, and reapplied it to where I thought it was needed. I also discovered that this stall is actually not one single piece. There is a base part from the ground to about 2 feet up. Then, one side of the wall has another piece of plastic and the other side of the wall has another piece of plastic that kind of connects like a puzzle (3 pieces total, and then the glass windows/doors). Anyways, I decided to apply a few layers of silicone, to ensure that no water would seap into the cracks where the 3 pieces of this shower stall meet each other.

I then, discovered that at the bottom corner of where the three pieces meet, there is a pretty large hole (you can probably fit a quarter in there), and just felt a very cold draft coming from it. Obviously, whoever put this washroom in place did not properly insulate behind it. I couldn't really put on silicone to cover this.

My question is, how do I properly 'plug' this hole so at least I can prevent cold air from coming through, and then put a good layer of silicone on there, to prevent water from doing any damage.

Thanks.

LawnGuyLandSparky

Where the shower wall kit pieces meet there is an overlap and the "joint" is already siliconed. Adding a layer of silicone over the exposed surface joint you can see after installation is redundant.