We have a 37 year old bi-level. We noticed that when you take a shower on the upper bathroom, water drips outside of the house under the siding where the bathroom is located. We now know we had some loose tiles and the seals were not that great, we plan to clean it all out and recauk it, but how do I know what damage has been caused behind the tiles? It this something serious? Is mold a big concern?

You have a broken discharge pipe that needs to be fixed asap. The continual water leaking from this pipe is damaging your floors, walls, etc. Just fixing the tiles and sealing it up on the outside is not the answer as the water will just be trapped inside the home and do great damage and possibly have mildew/mold problems soon.

If you had a full tile shower the problem may have been from leaks in the grout. I would open up the area underneith the shower and locate the leak problem before going any further. As far as mold, some will tell you your going to die from it and others will say its not such a bad thing. All depends on the mold. I would would fix the leak, spray a clorox type cleaner on the damp areas, make sure everything is dried out before enclosing. Hope this helps and please let us know how everything turns out.