We are remodeling/adding to a ~75yr old home in central TX Zone 3a, very near juncture of 2/3 a/b.  Current construction is Concrete piers, supporting large timber beams/floor joists.  Walls are 2×4 with diagonally run 1x for sheathing, and tar paper over that.  No insulation in the walls.  We want to save a portion of the exterior masonry walls, which sit on a concrete footing and isn’t otherwise tied to the structure (i assume there are wall ties).  What is best practice to build a modern wall behind this veneer?  My thought is to spray closed cell directly against the existing masonry and tie that into new wall, but i’m unsure if this will cause moisture issues in the rock wall.  The masonry is ~5″ thick dense limestones random cut avg 24″x24″ with thin (1/2″?) mortar joints. Open to all suggestions?