Jettying

Jettying (jetty, jutty, getee (obsolete) from Old French getee, jette) is a building technique used in medieval timber-frame 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. In the U.S., the most common surviving colonial version of this is the garrison house. Most jetties are external, but some early Medieval houses were built with internal jetties.

Structure

A jetty is an upper floor that depends on a cantilever 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 joists 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 joints.