Arches and Vaults: What They Are and Why They Matter

Arches and vaults keep buildings standing while creating memorable spaces. They move weight through compression, not bending, which lets architects span wide openings with less material. Want to spot them or use them in a project? Start with the basic types and how each handles forces.

Common types and how they behave

Round (Roman) arch: a semicircle. Strong in compression but pushes outward at the base, so you often see thick walls or buttresses. Think Pont du Gard or Roman aqueducts. Pointed (Gothic) arch: two arcs meeting at a peak. The point lowers lateral thrust, so vaults can be higher and slimmer—used in cathedrals like Notre-Dame. Segmental arch: a shallow arc with less rise; it produces less headroom but lower side thrust. Horseshoe arch: common in Islamic architecture (Great Mosque of Córdoba); offers a distinctive look and different proportions.

Barrel vault: an extended arch, like a tunnel. Easy to build but creates constant lateral thrust along its length. Groin (cross) vault: formed where two barrel vaults intersect—concentrates loads at corners so walls can be pierced with windows. Rib vault: a framework of ribs carrying the load; the infill can be thin, so rib vaults give large, light interiors (Gothic cathedrals again).

Design, proportions, materials, and retrofit tips

Quick rules of thumb: a true semicircular arch has a rise equal to half the span. Segmental arches often use a rise between one-quarter and one-third of the span. Pointed arches give flexibility—change the rise without huge side thrust. For vaults, remember that continuous barrel vaults exert uniform lateral force; groin and rib vaults focus loads so you can make lighter walls and add windows.

Materials matter. Stone and brick resist compression well but need mass or buttressing to resist thrust. Reinforced concrete and steel let you thin profiles and span farther with less support. Modern timber glulam arches offer a warm look and good strength for residential and small commercial projects.

Repair and retrofit tips you can use: repoint mortar joints on masonry arches to stop water ingress; install discreet steel ties across an arch’s springing points to control spreading; add external buttresses or internal ring beams when lateral thrust grows. For cracked vaults, crack stitching with stainless steel bars and grouts often stabilizes the span without stripping historic fabric.

Want to use arches in a modern interior? Try shallow segmental openings for subtle curves, expose a rib or vault as a feature ceiling, or combine a steel frame with thin masonry to get the classic look without massive walls. Arches and vaults are more than style—they’re a structural tool. Knowing which type fits your span, load, and aesthetic will save time and money and give your space real character.