Having owned a wooden-hulled 32' sailboat for a couple of decades, I know a bit about wood rot. Check marine supply places or maybe hardware stores for a product called "GitRot". It's a structural wood hardener referred to previously. Chop, scrape, dig out as much rot as you can, then apply the GitRot. It will penetrate the wood fibers before it hardens. I really hate Bondo. It is merely cosmetic, hides a multitude of sins - like when a big hunk falls of that 'cherry' used car you just bought off Craigslist - and is a bloody cheap way to 'fix' things - poorly. If you want to go that route, search out the West System of epoxies - also at marine stores. Again, this is something that penetrates wood before hardening. You could use a mix of low-density filler until you get the void back to near nominal dimensions, then finish off with a bit of fiberglass cloth. Fiberglass has to be protected from UV with paint. Cheers

From your description, the rim joist is rotted and must be replaced. To do this properly, the slider door has to be removed. The subfloor is attached to the rim joist, and the slider sits on the subfloor. There is probably a nail fin around the slider on all 4 sides, nailing it to the studs, header, and rim joist. When you take it out, you will be able to see the extent of the damage. Careful deconstruction of the deck and slider door will save you money. This is a pretty big job, very labor intense. Hopefully the subfloor is still in good shape, or part of that will also have to be replaced. When putting things back together, make sure the door opening is flashed properly. It should have sticky flashing on all sides and underneath, covering the framing, subfloor, and the rim joist, sticking to the house's weather barrier of tar paper or tyvek. Another layer of sticky flashing goes over the nailing fin. The metal flashing installs over that, tucking under the sill of the slider and over the ledger board. Another piece of metal flashing should tuck in behind the bottom of the ledger board, and come out over the siding below.

I believe the insulation has borates in it. Check with your supplier to make sure. I do know that bugs don't like it. It may be cheaper to install the icynene first and then just treat the wood left exposed. If you do decide to treat before insulating I'd also check with your supplier/installer about the effect of borate application on the ability of the product to stick to the wood.

Hi, fixinfool. Thanks for the email alerting me that you brought this one back up! I've been meaning to come over and update it, actually. OK, so here's the update. We did buy this house at the end of December. What ultimately happened with the floor repair situation was that my husband negotiated with the seller/seller's agent to lower the price of the house by around $20,000. This was done because the highest estimate obtained by the seller was just under $20K. It included fixing the sagging joists and getting rid of the mold. However, we were uncomfortable using this contractor because he did weird stuff in his estimate such as adding in a "20% markup" just as a line item. Another contractor (plumbing, not flooring/foundation) came out and while he didn't say anything bad about the $20K contractor, he expressed some level of surprise that the guy was in the floor-fixing business. That was enough for me to want to pass on it. And as it turned out, passing on it was a good thing because we got two or three more estimates, and finally found a guy who jacks up and levels floors for a living. Very down-to-earth guy who works with his father and son and it's something they've all done all their lives. He came in and told my husband what needed to be done and gave him an estimate, which included all materials, jacking up and leveling the floor, and replacing the damaged joists/adding new ones alongside to strengthen everything. He added concrete piers and something called "six buh sixes" (sorry, we live in TN and I'm from PA so my husband had to talk to the guy--I literally couldn't understand a lot of what he said, hehe). He also built a subfloor in an area of the house with a concrete slab (I think it used to be the garage, maybe). The total cost was $5,000 for all of it (including the materials and subfloor that he built). We had to pay him cash and buy the materials ourselves, but he provided us a list and told us what to get. He did a very, very good job. The floors are leveled out in all but one area, and he could not do that area because there is a heat/AC main duct going along the center of the house in the crawlspace. He could not move it to jack up that one small section. But what he did was add piers and joists (? not sure exactly) along either side to make sure that it was all structurally sound and fortified. It took him about a week to get it all done. When they were jacking the house, we were inside and could feel it. That was pretty cool. They would do a little at a time. They also said that one of the original joists was actually broken in half, so they replaced that and then added some sort of sistering thing alongside just to be sure. They did not remediate the mold or the damaged vapor barrier, however. For this, we found a termite guy. We are from Florida, and we used the Termidor system down there. I don't like bait systems; too iffy and "wait for disaster" for me and it's also dependent on technicians coming back and checking. Blech. No thanks. So we were at a home show and one of the termite guys had a Termidor sign. He was also kind of a skinny little fella, which seemed sort of like an advantage when it comes to crawling around in confined areas. This is what the termite guy did for us (it was a total of $3100). He treated the house with Termidor. It's a 3200-3400 sf house with about 800 feet on the second floor, I think. He removed the insulation under the house, which was mold-ridden, soggy, and gross-just a moisture magnet. He also removed the failing vapor barrier. He put up a new barrier for us. He treated the house (the crawlspace, I mean) to kill the mold and mildew. He also installed a vent system with humidity and temperature sensors that automatically starts running the fans if they rise above a certain level, to help prevent any future mold. We felt this was a good deal and we also liked the guy. This took him most of a week to accomplish. He incidentally found an HVAC duct that was separated and hanging down, just blowing hot air all over the crawlspace. Nice! No wonder our power bills have been nearly $500. We are not sure if this just happened or if it has been like this for a while. We also replaced the existing HVAC system and added a new one (we are remodeling an attic space and also adding central heat/air to a room that just had a window A/C unit) just before the floor guys/termite guys did their thing. The HVAC guys are coming out next week to do another duct inspection just to make sure it's all tight and stable under there. Geesh, this was long! I hope this answers some of your questions. The jacking up part of the foundation fixing was actually far less dramatic than I'd pictured it in my mind. I think what they did was check the floors for level (under the house) and then jack until they were level, then do whatever they do to the floors (joist fixing?/joist adding?) to support the floors at "level." Then they checked it again and moved on to the next area. I know there was a lot of wood (expensive wood) and a lot of concrete blocks involved in this process. Probably $2K worth of wood and concrete blocks? Sorry my descriptions are not incredibly technical, but I might be able to answer specific questions if you have them. The answers will probably not be all that technical but they might still work for you. Good luck, and thanks again to sdello, HancyMac and kudzu for helping me out!