Existing masonry can't be wrapped from outside on most projects, so this system works from the interior: a continuous smart vapor retarder as the airtight layer, insulation selected to keep the old wall's moisture balance workable, and disciplined tie-ins at windows, floors, and penetrations. The historic wall keeps doing what it has always done — the new layers manage air and vapor deliberately.

This documentation is general, principle-based guidance. Masonry retrofits are moisture-sensitive and building-specific; the assembly for your project should be reviewed by your design professional of record.