Even before we moved into this house we were aware of the structural issues - it doesn't help that the house was built badly to start with (vertical walls anyone?), but the lack of maintenance combined with badly installed gutters resulted in considerable rot in the wood structure where it meets the foundation. In some places it wasn't even a case of rot - the wood was long gone - taken away by water and insects attracted to wet wood.
I could have patched just a few places, but it would have been just that, so I decided to replace a 30 foot section - of course this meant I had to deal with supporting the house while I effectively completely removed one outside wall.
So, with summer in full rage, I supported internally and started yanking out rotten timbers. It was a horrific, dirty, sweaty job. For half of the span they had used a rim joist that was pressure treated. For the other half, it was mostly gone - in many places I could see outside from the basement before I removed anything.
Finally, over a period of weeks, I completed it - everything fully replaced with pressure treated lumber, and, all the doors and windows upstairs still worked - nothing had dropped. I also had to replace lots of structure above the basement where water splashing from the deck (broken/missing gutters) had got behind the siding. I'm very pleased to have got this done - it was by far the biggest house job I've done.