A pediment is a triangular or arched architectural element that crowns a door, window, portico, or gable end. It is one of the oldest devices in classical architecture for signaling importance: place a pediment over an opening, and the eye reads that opening as the significant one on the elevation. That is why pediments appear so consistently on courthouses, university halls, clubhouses, and other buildings designed to convey permanence and civic weight.
Pediment Definition and Origins
In classical Greek and Roman architecture, the pediment was the broad triangular gable end beneath a temple's sloped roof, framed by cornice moldings and frequently filled with sculpture. The U.S. Supreme Court Building is the canonical American example: a sculpted triangular pediment carried on a colonnade, borrowed directly from the classical temple front. As classical vocabulary migrated onto smaller buildings, the pediment scaled down with it, and the term broadened to include the triangular and arched elements placed above individual doors and windows.
Both senses remain in use today. On a modern project, “pediment” can refer either to a decorative element crowning a door or window opening, or to the ornamental element filling or trimming a roof gable. The two are different products with different installation conditions.
Pediment vs. Crosshead
The short answer: a crosshead is flat, and a pediment is not. A crosshead is a flat, horizontal prefabricated element installed above a door or window as a header trim. A pediment is the larger, more decorative version of the same idea — triangular or arched rather than flat, with a projecting profile that reads clearly from the street.
The two are often grouped together in product catalogs because they solve the same design problem at different levels of formality, and because keystones and other accents pair with both. A keystone block, for example, is typically added to the center of a crosshead for additional visual emphasis — covered in more depth in our guide to arches and keystones. To compare pediment and crosshead profiles side by side, browse the pediments and crossheads in our Shape Finder tool.
Types of Pediments
Most pediments fall into one of five categories. The first four crown door and window openings; the fifth belongs to the roofline.
Triangular Pediments
The classical default: two raked cornices rising to a central peak over a horizontal base molding. Triangular pediments suit Georgian, Federal, Colonial Revival, and Neoclassical elevations, and they remain the most commonly specified profile for formal entrances on institutional buildings. When the design intent is simply “classical, correct, and quiet,” this is the profile.
Segmental (Arched) Pediments
A segmental pediment replaces the peak with a shallow curve — a segment of a circle — over the same horizontal base. Sunburst and fanlight variants fill the arched field with radiating fluting for additional visual interest. Segmental pediments soften an elevation and pair well with arched transoms and round-top windows; alternating triangular and segmental pediments across a series of window bays is a classic technique for adding rhythm to a long facade, particularly on multifamily and hospitality buildings.
Broken Pediments
A broken pediment interrupts the raked cornice at the peak, leaving an open center that traditionally frames a finial, urn, or cartouche. The device dates to Baroque architecture and carries more ornamental ambition than a closed profile. On contemporary projects it appears most often at primary entrances where the design calls for a focal point with genuine presence.
Swan Neck (Scroll) Pediments
A swan neck pediment, also commonly known as a ram's head pediment, is a broken pediment whose raked cornices curve into opposing S-shaped scrolls, usually flanking a central finial. It is a signature of Georgian architecture, familiar from 18th-century doorways and high-style casework, and it remains the most formal profile in the pediment family. Specify it where a single entrance needs to carry the architectural weight of an entire elevation.
Gable Pediments
Gable pediments return the term to its original meaning: ornamental elements that fill or trim the triangular gable end of a roof rather than crowning an individual opening. Common patterns include traditional trusswork, sunburst infill, and Victorian gingerbread profiles. Because gable pediments mount to the wall plane inside the gable and must match the roof pitch, they are a different product and a different installation condition than door and window pediments.
Where Pediments Are Used
On today's large-scale projects, pediments concentrate in four locations. Main entrances are the most common: a pedimented entry on a government building, university hall, or clubhouse establishes the front door at a glance, even on a long, otherwise repetitive elevation. Window heads are the second: pedimented window surrounds at the primary floor level are a reliable way to give a facade classical structure without ornamenting every opening. Porticos are the third: the full temple-front treatment, with a pediment carried on columns, remains the defining gesture of civic and institutional architecture. And gable ends are the fourth, wherever a roofline faces the street or a courtyard.
Pedimented Dormers
A pedimented dormer is a dormer window whose small gable roof is finished as a pediment, with raked cornice returns and a base molding. On buildings with residential massing, like senior living communities, student housing, inns and lodges, a run of pedimented dormers is often the single most visible classical detail on the building, repeated a dozen or more times across the roofline. That repetition is exactly why molded composite dormer pediments are worth considering: a profile that is cast once and produced consistently avoids the variation that shows up when trim carpenters build the same detail twenty times in the field.
Pediment Materials: What to Specify
Historically, pediments were built up from wood moldings or carved from stone. Both remain available, and both come with the maintenance and cost profiles you would expect: wood requires ongoing paint maintenance and is vulnerable to rot at exactly the horizontal ledges a pediment creates, while carved stone is heavy, slow, and expensive. On most current projects, pediments are specified in molded composite materials instead.
Polyurethane is the standard for door, window, and gable pediments. High-density polyurethane is molded with crisp, consistent detail, has a smooth paintable surface that closely resembles finished wood, and is light enough that most units install with adhesive and standard fasteners — a meaningful labor advantage when a pediment repeats across an elevation. It is also generally the most cost-effective option for standard profiles and larger production runs. For a fuller comparison of composite trim materials, see our resources, polyurethane vs. PVC and the best exterior trim material types.
Cellular PVC is another option. Molded materials like polyurethane and fiberglass require tooling, and for a one-off entrance profile or a short run of custom window heads, the mold and setup charges are hard to justify. A pediment fabricated from cellular PVC delivers the custom profile without the tooling cost and with the same paintable, moisture-proof performance PVC brings to the surrounds, casings, and flat trim around the pediment.
Fiberglass and GFRC work when the pediment moves beyond standard scale. Portico pediments, oversized entrance compositions, and historic replication work (matching an existing profile on a restoration or an addition) are typically custom-molded in fiberglass, or in GFRC where a stone-like appearance and mass are part of the design intent. Our guide to historic building restoration with modern materials covers how molded composites are used to replicate original ornament at scale.
Specifying Pediments for Your Project
A few coordination items keep pediment submittals clean. First, size the pediment to the opening: door and window pediments are dimensioned to the overall width of the opening plus its surround, so confirm whether the pediment sits on the casing or spans it.
Second, coordinate with the rest of the surround…pediments are frequently specified as part of a system with pilasters, casings, or a full door surround, and the profiles should be selected together rather than mixed from different families.
Third, confirm the mounting condition: door and window pediments mount to the wall plane above the opening, while gable pediments must match the roof pitch shown on the drawings.
Finally, note the finish requirement: molded composites arrive primed and are painted in the field.
Decoro Building Products manufactures pediments in polyurethane and cellular PVC for standard door, window, and gable applications, with custom fiberglass and GFRC capabilities for portico-scale and historic replication work. To get project-specific answers, request shop drawings, a submittal package, or a take-off from your drawings.