Exterior wall rehab – concrete/wood barrier question – GreenBuildingAdvisor

Hi folks,

We are doing a major rot remediation project. The house has a 4″ masonry shelf that was used to support a stone veneer. The veneer had to be removed because of substantial water-related damage. From the exterior, the sheathing is no good and the rim joists are no good. The finished grade all around the house has hardscapes, garages etc that were installed at an elevation equal to the top of the rim joist.

So the remediation plan is to remove the rotten sheathing, improve the R value of the existing 2×6 wall and replace the rotten rim joists with 2×10 PT rim joists. Then, use the masonry shelf to build a second studded wall. The second wall will be 2×4 with a thermal break to the existing wall.

We can preserve all of the existing improvements and their grades if we pour a 4″Wx10″H continuous concrete wall on the existing masonry shelf, against the new PT rim joists.

My question is how best to forever separate (and protect) the PT rim joist that will be sitting behind that new concrete? I have attached a sketch if that helps explain.

Thank you.

Steve