So I knew I had a problem when we bought the house a few months ago with the air handler closet. It appears the condensate drain line was plugged and was not allowing the pan to drain properly. Water seems to have been over flowing the pan onto a poured concrete floor. The water found its way thru cracks to the wood floor joists and they were rotten. I made the seller make repairs to the drain line and rotten floor joists. House passed inspection so I'm thinking I'm good for now. I knew I still had some more work to do but other things came first. Well we had some hot days lately and we had the AC on. I noticed the condensate line on the outside of the house was not dripping. So.....I opened up the AC closet and the floor and filter was wet. It seems the air handler is not sitting level and the pan is tilted away from the pan drain.
I started looking around and decided to poke at the studs and the walls. The walls are covered with asbestos "millboard". Is hard and about 3/16" think. I doesn't get soft when wet like drywall does so who knew that the framing was totally rotted. I removed the millboard and the bottom 1" of studs were completely rotten away. The bottom horizontal plate of the wall framing crumbed in my hands. I could pull the nails out with my fingers. The tongue and grove subfloor was also shot.
Here is a pic.......
