Architectural Elements
Keystone
A keystone is the wedge-shaped stone at the apex of an arch, historically the final piece inserted to lock the arch's structure in place. In architectural terminology, the keystone is both functionally critical and symbolically significant—representing completion and the key to structural integrity. Decoratively, keystones are often enlarged, carved, or ornamented to emphasize the arch's crown.
Interior keystones appear above arched doorways, windows, and fireplace openings, serving as focal points that draw the eye to the arch's highest point. Whether structural or purely decorative, keystones add classical detail and visual weight to arch compositions. They can be simple projecting blocks or elaborately carved faces, scrolls, or decorative forms.
Key Characteristics
- ✓Central arch stone
- ✓Wedge-shaped form
- ✓Often enlarged/decorated
- ✓Structural and decorative
- ✓Focal point of arch
- ✓Classical architectural element
Types & Variations
Plain keystone (simple projection)
Carved keystone (decorative face)
Scrolled keystone (volute details)
Mask keystone (face/figure)
Oversized keystone (emphasized)
Works Well With These Styles
Placement & Usage Tips
Keystone size should relate to arch scale—larger arches warrant more substantial keystones. Project keystones slightly beyond the arch face for shadow and emphasis. Ensure secure mounting for decorative keystones.
💡 Pro Tip
Polyurethane and resin keystones offer lightweight, detailed options for decorative applications where structural performance isn't required. Prime and paint to match surrounding millwork for integrated appearance.