When doing remodeling work, I often come across rotten sills and joists. Should I remove these or can I leave them in place?
Rot is caused by living fungi that can be creating health hazards for building occupants. If the rot is in its early stages, you can eliminate it by creating conditions which are not conducive to living fungi. Since fungi thrive between 32°F and 100°F and need water and oxygen, eliminating one or all of these elements will kill the fungi and prevent further damage.
The easiest way to stop the rot is to keep the wood dry (under 22% moisture content). Find where moisture is coming in to the home and patch the holes. Then use a heater or fan to dry the wood out.
You can sister joints into wood once rot is dealt with, but then you run the risk of it reoccurring should moisture content rise above 22%. To prevent rot, treat wood with an anti-fungal spray. Once you have sprayed the wood, allow it to dry completely before replacing joists. Always resolve your moisture problems before dealing with rot or replacing sills and joists.