"So, the question is, if my sill plate does NOT have rot and is NOT
disintegrating due to termites, is it possible to patch the sill
plate? Or should I undertake the expensive task of replacing it?
The primary purpose of the sill place is the spread the load of the joist.
If "significant" wood has been eaten away your sill plate isn't really
spreading the load but only acting as a cushion between the joist and the
Frankly, the odds are good that the termites have gotten into the joists
either through the sill plates or via the "end plates."
Do the "philips screwdriver" test and do some hard probing of the sill and
the joists. You may well find that what looks like sound wood is actually