Illustrated glossary of architectural terms


See also "Common Roof Trusses in Surrey" by Joan Harding & Martin Higgins.

PurlinLongitudinal roof timber supporting rafters between apex and wall plate.
   Butt purlinPurlins joined end to end or into the end of a bay.
   Clasped purlinPurlin held against the principal rafter by a collar,queen strut or raking strut.
   Collar purlinPlate supported on crown post and bearing the collar.
   Staggered butt purlinPurlin in one bay out of line with purlins in adjacent bays.
Dragon beamA horizontal timber which runs diagonally into a corner angle, into which floor joists are tenoned.
CollarTransverse beam connecting the mid-points of the sloping rafters of a pitched roof.
Crown postVertical timber standing on tiebeam and supporting collar purlin.
King postPost standing on a tie beam or collar to support a ridge piece.
Queen strutsPaired struts between tie-beam and collar, not supporting a longitudinal timber.
   Raking Queen strutsPaired struts at an angle to the tie-beam, framed into the principal rafter.
RafterSloping parallel roof timbers supporting tiles or other cladding material.
Ridge pieceLongitudinal timber at apex of roof.
Sans-purlinRoof with no purlins (q.v.).
Tie beamBeam connecting the two slopes of a roof across at its foot, usually at wall plate level.
TrussFramework across a roof at intervals carrying longitudinal timbers
Wall plate A timber laid along the top of a wall to receive the ends of rafters, tie beams and ceiling joists.

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©DBRG 19 September 2008