Rebuilding a Failed Brick Arch Over a Doorway
A homeowner had a brick arch over their front door that had developed a visible crack and a slight sag at the center. The door beneath still worked, but the arch looked wrong, and they worried it might eventually collapse. An arch is a structural element, so the concern was legitimate. The good news is that a failed arch can be rebuilt to be as strong as the day it was laid, if it is done correctly.
A brick arch works entirely in compression. The wedge-shaped bricks, called voussoirs, transfer the weight above the opening outward and down into the supporting jambs. An arch fails when something disrupts that compression path. Often the supporting columns or jambs spread slightly, the center drops, and the joints crack. The fix is to dismantle the arch, restore the supporting geometry, and rebuild with a proper template so every voussoir is correctly placed.
We shored the masonry above the opening, carefully dismantled the failed arch brick by brick, and inspected the supporting jambs. One jamb had settled slightly, which is why the arch dropped. We corrected the bearing and rebuilt the arch over a wooden template, or centering, that held the exact curve until the mortar set. Each brick was placed as a true voussoir, with mortar joints tapered to carry compression. The craftsmanship is the same we apply across our masonry repair and historic preservation work.
We matched the brick and mortar to the original so the rebuilt arch blends with the surrounding wall. Once the mortar cured, we removed the template, and the arch carried its load as designed. The crack is gone, the sag is corrected, and the entry looks as it should. The homeowner kept the architectural character of their home and gained a structurally sound opening.
Arch repair is a good example of why masonry is a craft as much as a trade. The geometry has to be right, or the arch will fail again. A contractor who simply mortars the crack closed has not addressed the compression path, and the crack will reopen. The same principle applies to lintels and any spanning masonry. See related structural work in our building and structural restoration services.
If you have a brick arch that has cracked, dropped, or shifted, have it evaluated before it worsens. Arches rarely fail suddenly, but once the compression path is broken, deterioration accelerates. Contact us for an assessment.
An arch is geometry made of brick. Respect the geometry, and it will hold for a century. Ignore it, and it will tell you by cracking.
