Rim Joist Repair/replacement guidance help

Hello. I've got some pretty good pictures to detail what I'm explaining. My back deck had a hot tub when I bought the house, they placed it about 2 inches away from the wall. Leaves gathered behind it all the time and got wet. I tried to keep it clean but hard to get back there and got a bit lazy. At one point about 5 years ago had some carpenter ants try to move in, but I got on that quick, cleaned out and treated/killed them myself and had it looked at by exterminator and he saw no problems. I get quarterly treatment and checks.

Anyways, during a bunch of other work, the tub was so old etc. I took a sawsall and just cut it into pieces and trashed it. During this process noticed some damage to the siding at the base behind the tub. The siding is rotted, pulled away and began digging into the rim joist. On the outer side there is dry rot for about 4 feet in length, at one point all the way through to see the sill, and some of the flooring dry rotted on the outer edge above the rim joist. Checked in the crawlspace, floor joists are fine, and felt and poked around the sill, it seems fine. The flooring under the house is not rotted or warped, a little dark stained from the water but seems ok other than the edge on the outside. Could this be supported by sistering support flooring between the floor joists? I don't want to tear up carpet etc. that''s all only about a year old.

There is no visible settling of the floor/house, no cracks, etc., mainly because the damage is pretty much right in the middle of the wall so plenty of good rim joist on both sides. There are no signs of termites or termite damage, but will have the exterminator verify.

So searching around I'm thinking from different things I've seem that a contractor should be able to cut out the damaged portion of the rim joist and replace it, and then sister it to about 3 floor joists with sister supports on the floor joists and using bolts and metal corner brackets on the rim joint and sisters.

Looking at the pictures, does this seem viable, and I wonder what an estimate would be? Thanks.

To View the 4 photos click below:

http://www.flickr.com/photos/104285992@N02/10095846505/in/photostream/

It looks to me the biggest problem is how the deck was attached to the house. What is holding the deck up along that wall?

I added another photo, not real clear because I took it at night, but there are lag bolts about every 18 inches attaching the end deck joist to the rim joist, in the rotted portion you can see the bolt, i can actually see the end of the bolts with tip and threads, and of course on the top nails from the end of the deck boards down into the deck joist.

So if a section of that deck joist were removed that should provide full access to the rim joist from the outside, yes? There are plenty of support posts and a longer section of the deck joist to support the deck, obviously enough because right now the lag bolts aren't connected to anything in that area and nothing moves at all when you step in that area on the deck, so their main function just seems to be anchoring the deck to the house, not supporting the deck really in any way....

I would say your plan seems to be the way to go for the rim joist, any wood that may contain rot but that will be left in place like the plywood floor should be treated with a copper base where ever it is exposed before rebuilding. Lumberyards carry the stuff much like the green treatment on the deck. The main thing that was missing here and likely would have prevented this was flashing.
Hot dipped steel gavinized deck flashing goes behind the siding and house wrap or tarpaper and over the deck joists and is trimed at deck joists so it sits flat on the deck rim under the deck boards.

Glad I was able to convey it properly, your illustration is perfect The house was built in 1986 so I'm not sure what the code was then here in Virginia and my county as far as the flashing, I will definitly get at least that section flashed. I wanted to make sure I seemed fairly up to speed when I get estimates so I don't get ripped off for probably unneeded repair like replacing the entire length of the rim joist and flooring if not needed, talking tons of money there not to mention ripping up carpet, etc. I see no reason it can't all be sistered up. I really appreciate it. If I have more questions I'll post back (I'm sure I will after the estimates) and will post pictures of the repairs. Thanks again!