Ashlar
Ashlar is a type of masonry construction characterized by the use of finely cut and dressed stone blocks, typically rectangular or cuboid in shape, that are precisely fitted together with thin mortar joints to form smooth, uniform surfaces.[1][2] These blocks, often sourced from quarried stone like limestone or sandstone, are worked to achieve exact dimensions and finishes, distinguishing ashlar from coarser rubble masonry.[3] As the highest grade of stonework, ashlar emphasizes durability, aesthetic elegance, and structural integrity, allowing for both load-bearing walls and decorative facades.[3] The technique has ancient origins, dating back to civilizations such as Egypt around 2600 BC, where it was employed in the construction of the Great Pyramid of Giza using millions of precisely cut limestone blocks.[1] In classical Greece and Rome, ashlar masonry became prominent in monumental architecture, exemplified by the Parthenon in the 5th century BC and the Colosseum in the 1st century AD, showcasing advanced quarrying and fitting methods.[1] During the Middle Ages, it featured extensively in Gothic cathedrals like Notre-Dame in Paris and Canterbury Cathedral, while the Renaissance revived its use in classical revivals, as seen in structures such as the Palazzo Medici Riccardi and Château de Chambord.[1] This enduring application across eras highlights ashlar's role in conveying permanence and prestige in buildings.[2] Ashlar masonry encompasses several types based on layout and finish, including coursed ashlar, where uniform blocks are arranged in horizontal layers for a formal, rhythmic appearance; random ashlar, featuring varied stone sizes without a strict pattern for a more rustic effect; and chamfered ashlar, with beveled edges to add subtle ornamentation.[1][2] Surfaces can be smooth or rough-tooled, with chisel marks providing texture while maintaining precision.[2] Commonly used in exterior walls of residential, civic, and monumental buildings—such as town halls, libraries, bridges, and cathedrals—ashlar provides weather resistance and visual appeal, often serving as a veneer over rubble or brick cores to achieve thin, tight joints under 0.5 inches.[1][3] Its construction demands skilled stonemasons and can be mortarless in dry-stone variants, underscoring its technical sophistication.[1][3]Definition and Characteristics
Physical Properties
Ashlar masonry is constructed using dimension stones selected for their mechanical and durability properties, which vary by material type such as limestone, sandstone, and granite. These properties are standardized by ASTM International and ensure the stones' suitability for load-bearing and exposed applications. Key properties include compressive strength, density, and water absorption, as outlined below for common types (ranges based on ASTM classifications; specific values depend on the stone variety and quarrying).[4]| Stone Type | Compressive Strength (psi) | Density (lb/ft³) | Water Absorption (% by weight) |
|---|---|---|---|
| Limestone (ASTM C568) | 1,800–35,000 | 110–185 | 0.2–29.0 |
| Sandstone (ASTM C616) | 2,000–37,000 | 125–170 | 1.0–20.0 |
| Granite (ASTM C615) | 4,700–60,000 | 150–200 | 0.02–0.70 |