Flanged Window

1. Apply a vapour-permeable air barrier membrane (sheet, self-adhered, or liquid applied) onto the window rough opening and surrounding wall area. Install extended membrane flashing at the window sill to shed water from the window rough opening out over the exterior insulation.
2. Install flanged window and fasten through strapping at the head and jambs, and intermittent blocking at the sill flange for drainage.
3. Install self-adhered membrane flashing over the window head and jamb flange.
4. Install metal flashing at the window sill to extend over exterior insulation and siding.
5. Place rigid mineral wool insulation over air barrier membrane. Use pressure-treated wood strapping or plywood aligned with stud spacing where possible. Attach with screws through the insulation into the existing wall.
6. Install metal flashing onto strapping above the window head to deflect moisture out over the window.
7. Install exterior siding. Most cladding types are well supported by the strapping and screws. Heavy weight cladding like stone veneer or brick may require additional support.
8. Install finish trim (or cladding returns) where needed to cover the depth of the exterior insulation on all exposed sides.