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Jettying

 
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Jettying is a building technique used in medieval timber frame
Timber framing

Timber framing , or Half-timbering, is the method of creating framed structures of heavy timber jointed together with pegged mortise and tenon joints....
 buildings in which an upper floor projects beyond the dimensions of the floor below. This has the advantage of increasing the available space in the building without obstructing the street.






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Doublejettiedbuilding
Jettying is a building technique used in medieval timber frame
Timber framing

Timber framing , or Half-timbering, is the method of creating framed structures of heavy timber jointed together with pegged mortise and tenon joints....
 buildings in which an upper floor projects beyond the dimensions of the floor below. This has the advantage of increasing the available space in the building without obstructing the street. Jettied floors are also termed jetties.

Structure

A jetty is an upper floor that depends on a cantilever
Cantilever

A cantilever is a Beam supported on only one end. The beam carries the load to the support where it is resisted by Moment and shear stress. Cantilever construction allows for overhanging structures without external bracing....
 system in which a horizontal beam, the jetty bressummer, supports the wall above and projects forward beyond the floor below (a technique also called oversailing) . The bressummer (or breastsummer) itself rests on the ends of a row of jetty beams or joist
Joist

A joist, in architecture and engineering, is one of the horizontal supporting members that run from wall to wall, wall to beam, or beam to beam to support a ceiling, roof, or floor....
s which are supported by jetty plates. Jetty joists in their turn were slotted sideways into the diagonal dragon beams at angle of 45° by means of mortise and tenon
Mortise and tenon

Simple and strong, the mortise and tenon Woodworking joints has been used for millennia by woodworkers around the world to join pieces of wood, usually when the pieces are at an angle close to 90?....
 joints.

The overhanging corner posts are often reinforced by curved jetty brackets.

Vertical elements

The vertical elements of jetties can be summarized as:
  • the more massive corner posts of the timber frame that support the dragon beam from the floor below and are supported in their turn by the dragon beam for the extended floor above.
  • the less substantial stud
    Stud

    Stud may refer to:* Stud , an animal retained for breeding* Stud farm, a property where livestock are bredObjects:* Shirt stud, a small ornamental button...
    s of the close studding
    Close studding

    Close studding is a form of timber work used in Timber framing buildings in which vertical timbers are set close together, dividing the wall into narrow panels....
     along the walls above and below the jetty.


Horizontal elements

The horizontal elements of jetties are:
  • the jetty breastsummer (or bressummer), the sill on which the projecting wall above rests; the bressummer stretches across the whole width of the jetty wall
  • the dragon-beam which runs diagonally from one corner to another, and supports the corner posts above and is supported by the corner posts below
  • the jetty beams or joists which conform to the greater dimensions of the floor above but rest at right angles on the jetty-plates that conform to the shorter dimensions of the floor below. The jetty beams are morticed at 45° into the sides of the dragon beams. They are the main constituents of the cantilever system and they determine how far the jetty projects
  • the jetty-plates, designed to carry the jetty-beams or joints. The jetty-plate itself is supported by the corner posts of the recessed floor below.


See also

cantilever
Cantilever

A cantilever is a Beam supported on only one end. The beam carries the load to the support where it is resisted by Moment and shear stress. Cantilever construction allows for overhanging structures without external bracing....
 - modern buildings still use cantilevered floors, but the term jettying is rarely used. See for example the Whitney Museum of American Art
Whitney Museum of American Art

The Whitney Museum of American Art, often referred to simply as "the Whitney", harbors one of the most important Collection of 20th century United States art....
, New York.