Clay roofing tile problem??!

[Chris Low]

We looked at a house today that has a Spanish-style clay tile roof, which is not that common in our area. The house is in pretty good shape, with a few notable exceptions including a big hole in the master bedroom ceiling. However, when we went in to the garage and looked up into the rafters, we can see the clay tiles just sitting on the rafters with no apparent underlayment material whatsoever. We were able to see up in to the hole in the master bedroom and, sure enough, you can see the under side of the clay tiles there also. In the picture below, you can see what I'm talking about. You can also see that the dark spots on the tiles are moisture (it's been raining hard here.) We were shocked to see that there's no underlayment on this roof and the research we've done on installing clay tiles all indicates that there should be. It looks like the entire roof was installed this way. The house was built in 1985. Hoping some contractors/home inspectors/roofers can give an opinion. Is this normal? Is it Code compliant (California)? Are we going to have to replace the entire tile roof because of this? Any help would be much appreciated.