How to Insulate a Brick Wall Overlay

Run a wall stud finder over the wall to locate the stud locations. Mark the locations of each wall stud with a piece of chalk.

Install a sheet of metal flashing along the base of the wall, extending 12 inches up the wall face and outward from the wall base an additional 6 inches so that the overlay can sit on the flashing while maintaining the necessary inch of space between the rear of the overlay and the front of the insulation. Connect the flashing to the wall using a fastener that’s compatible with the wall type, spacing the fasteners through the wall at the location of every wall stud.

Place a layer of builder’s felt over the wall. Fasten the felt in place using compatible wall fasteners, placing one every 2 feet on center throughout the wall. Use a utility knife to cut the felt along openings in the wall. Cut a sufficient amount at the openings to overlap the edges of the opening completely so you can install the window or door over a layer of felt along its edge.

Place the first row of foam insulation boards horizontally across the base of the wall where you’re installing the overlay. Mount the boards to the wall using the appropriate fastener for the wall material type; for example, use concrete screws for masonry walls or staples, placed with a pneumatic stapler, for wood sheathing. Attach the fasteners at the stud locations, spacing them every 8 inches along the stud line. Butt the ends of the foam boards closely together, and cut them when needed to fill short spaces at the edge of a wall or to fit around a window or door opening with a utility knife.

Set the next row of foam boards above the first, and continue building upward in rows until you reach the top of the wall.

Cover the joints between the boards with strips of fiberglass tape to prevent the escape of heat from between them.

Install the overlay as normal, running the base of the bricks over the flashing to aid with water drainage and maintaining a space of between 1 and 2 inches between the bricks and the foam surface for airflow.