Flooring Tile - Tile, Mold, and rot...oh my...

OK this may be a little long but hang in there with me. Just moved in to a 10 year old house last week. I knew when I purchased it that the bath room shower pan needed to be re-calked so I started on that yesterday. While removing the old calk in front of the shower door, I found that the grout around the tiles that butt up to the shower pan was loose and crumbling. To make a long story short I removed one tile and found Black Mold. Great. Not too much about 1 square foot worth. Now I can clean the mold up, and replace small part the subfloor that feels spongy. I can do this no problem.

Now for the million dollor question: The tile that had the mold underneth was mortered directly to the subfloor. No backer board. So how do I put the tile back on? If I morter it directly to the sub floor won't I just have the same problem again even if I caulk really well? If I NEED a backer baord then I will have to tear up ALL the tile so the floor is level. :wall: Is there a happy middle groud here?

Thanks in advance.

To make a long story short I removed one tile and found Black Mold. Great.
You need to stop watching Dateline and 20/20. ;)

Your whole desription of the shower and damaged area has me concerned though. Ant chance you could post some pics? Use a free online photosharing service such as photobucket.com if your internet provider does not include a chunk of web space with your service, the post the link to the photos here.

Well I just moved a week ago so the digital camera is in a box somewere... But I assure you there is mold and it is black in color. I think what casued it was a half a** caulking job where the floor tile meets the shower pan and a lack of a seal between the bottom of the shower door and the shower pan. Like I said it's only a small patch 1 square foot worse case. The real question is how add protection to the floor.