waterproof insulation

[GMCGarage]

I have a contractor working on a job and the rim board/sill plate needs to be replaced, & joists need to be fixed.
Due to the house being bricked, it will need to happen from inside. One idea I had was sister on the joist ends, and then between the joists put some insulation between the brick and a new block of wood between the joists. this way I can get the new blocking fastened to the sill plate on the floor, and the sill on the foundation, giving lateral capacity.

My dillema is what insulation to use. It will be against brick on one side, and wood on the other. I was thinking some closed cell styrofoam.

Thoughts?

 

[8mpg]

closed cell foam

 

[Chris705]

Blue or pink foam sheets of XPS expanded polystyrene is waterproof.....available in many thicknesses and easily cut into strips/squares.

Don’t use polyisosanurate if using used CL find..... commonly found on roofing tear offs.