My shop is a 65 year-old two car garage.  On one side, the concrete foundation is only 2-3 inches above grade.  Changing the grade is not an option because of my wife’s flower bed.  About 20 years ago I replaced the sills on that side with pressure-treated 2x4s and they’re still in good shape.  I replaced the bottom row of pattern 106 siding 10 years ago but that rotted out pretty quickly.  This time, I’ve made up some of my own pattern 106 out of pressure-treated material which I think will last. 

My question is what type of caulk or adhesive would work best between the new siding and the foundation? The foundation is pretty uneven so there are gaps here and there which are between 1/8″ and 1/4″.  I’ll also need an adhesive bed to set a new pressure-treated sill for the shop door.  Again, the foundation is uneven and not very level so I’ll need to do a fair amount of shiming before I put the door sill down.

Chip