Replace a corroded steel lintel showing rust-jacking damage in a masonry wall

Steps

1. Confirm rust jacking as the cause: expanding corrosion product on an embedded steel lintel or shelf angle delaminating and displacing the surrounding masonry, distinguishing it from unrelated settlement cracking.
2. Assess section loss on the existing steel; once corrosion has consumed a significant portion of the original cross-section, plan for replacement rather than cleaning and recoating in place.
3. Shore the opening from below (adjustable posts or needles) before removing any masonry, keeping shoring in place until the new lintel is set and the mortar has cured.
4. Remove masonry above the lintel in measured sections, salvage reusable units, cut out and remove the corroded lintel, and install a new lintel (commonly hot-dip galvanized steel) sized for adequate bearing length on each side of the opening.
5. Install continuous flashing over the new lintel, lapped behind the wall's water-resistive barrier, with weep holes above the lintel, before toothing in matched brick and repointing.
6. Obtain a building permit and required inspections for this work, since lintel replacement is structural work in most jurisdictions, not routine maintenance.