In removing the old doors to the deck the other week, I noticed some spongy spots in the siding at the level of the deck. So I removed one of the boards of the deck, and started scraping at the ledger board. I scraped, then dug, then stopped when I couldn't reach any more with a putty knife and still hadn't found the bottom. Not surprisingly, I decided the ledger board and that piece of siding had to be replaced.
It's not the first repair I've made to the deck. Even with my limited building skills back then, when I bought the house I knew that the deck hadn't been built quite right; for one thing the boards were a little too close together, which meant pine needles and other cruft were going to get stuck. Since then I've replaced one of the joists and a couple of the posts because of rot. So finding this wasn't any big surprise.
I removed the ledger board and a piece of siding, and let things dry out overnight. The ledger board was attached well enough with lag screws, but unfortunately they weren't galvanized, so they'd begun rusting. That's the kind of thing that leads to news stories about 'deck collapses during party, injuring dozens'. The screws let loose, the deck isn't attached to the house, things rack, and off it goes. These screws weren't too bad, but not great, either.
Inspecting things in better light and after it'd dried, I discovered that the rot had spread into the rim joist, too. And then I looked more carefully, and realized some of the missing wood was due to termites, because there were little tunnels and pellets, even into the redwood siding. No live termites, fortunately.
Time to break out the sawzall (actually I used it for removing some of the siding, too) and attack the rotted bits. I finished removing stuff this afternoon, replaced the part of the rim joist, and got part way into re-applying siding.
All this could have been prevented for less than $10, using galvanized lag screws and a little bit of flashing. These days with pressure-treated (PT) wood, you have to be careful about what sort of metal you put next to PT wood, so rather than replace all the joist hangers as well as the ledger board I replaced the it with more redwood.
Supposedly the deck was built by a brother or brother-in-law of one of the former owners, and he built decks, etc. as a profession. (And the materials were paid for using the insurance money from when one of the neighbor's cars rolled down the hill and dented the corner of the house. No, really.) Given the problems I've seen with the deck, I'm really hoping this guy has either learned more or isn't building decks for a living any more. Because this is how not to build a deck.
P.S. Go Bears! Cal beat Texas A&M yesterday quite handily in the Holiday Bowl. Another 10 win season, and co-champs of the Pac-10. I'm sorry you weren't here to see it, Dave. Though I'm sure you watched it from a blue and gold cloud somewhere.