Keystone (architecture)




This article is about the architectural element. For other uses, see Keystone (disambiguation).




Voussoir stones of an arch




Keystone from the palazzo Borgazzi (Milan, Italy)




Dropped keystone at Colditz Castle


A keystone (also known as capstone) is the wedge-shaped stone piece at the apex of a masonry arch, or the generally round one at the apex of a vault. In both cases it is the final piece placed during construction and locks all the stones into position, allowing the arch or vault to bear weight.[1][2][3] In both arches and vaults, keystones are often enlarged beyond the structural requirements, and often decorated in some way. Keystones are often placed in the centre of the flat top of openings such as doors and windows, essentially for decorative effect.


Although a masonry arch or vault cannot be self-supporting until the keystone is placed, the keystone experiences the least stress of any of the voussoirs, due to its position at the apex.[4] Old keystones can decay due to vibration, a condition known as bald arch.


In a rib-vaulted ceiling, keystones may mark the intersections of two or more arched ribs. For aesthetic purposes, the keystone is sometimes larger than the other voussoirs, or embellished with a boss. Mannerist architects of the 16th century often designed arches with enlarged and slightly dropped keystones, as in the "church house" entrance portal at Colditz Castle (see image). Numerous examples are found in the work of Sebastiano Serlio, a 16th-century Italian Mannerist architect.




Contents






  • 1 Gallery


  • 2 See also


  • 3 Notes


  • 4 External links





Gallery






  • Keystone much enlarged for decorative effect, and carrying a coat of arms, Barcelona







  • The York Minster Chapter House rib-vault ceiling with central and peripheral keystones







  • A boss depicting Jesus Christ decorates the keystone in the rib-vaulting at Chapel of St. Anne in Malbork, 14th century.







  • Bossed keystone in the ceiling of an apse chapel (Toulouse Cathedral)







  • Arches with equal-size voussoirs and keystones, Mosque of Cordoba, Spain







  • Dropped keystone on a German church







  • Doors and windows with decorated keystones, Munich







  • A range of plain but enlarged keystones by Giulio Romano for his house in Mantua






See also



  • Architectural sculpture

  • Coping (architecture)

  • List of classical architecture terms


  • Oculus compression ring



Notes





  1. ^ Ching, Francis D.K. (1995). A Visual Dictionary of Architecture. New York: John Wiley & Sons, Inc. p. 12. ISBN 0-471-28451-3..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output .citation q{quotes:"""""""'""'"}.mw-parser-output .citation .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .citation .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-maint{display:none;color:#33aa33;margin-left:0.3em}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}


  2. ^ "Glossary of Medieval Art and Architecture – Keystone". University of Pittsburgh. Retrieved 2007-06-25.


  3. ^ "keystone". Merriam Webster. Retrieved 2007-06-25.


  4. ^ "Windows and More About Arches". Retrieved 2007-06-25.




External links


Media related to keystones at Wikimedia Commons








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