A Guide to the Repair of Historic Roofs - Dublin City Council

ROOFS A GUIDE TO THE REPAIR OF HISTORIC ROOFSMORTICE-AND-TENON JOINTThe commonest form of joint between timbersmeeting at right angles or oblique angles; the end ofone piece is stepped to form a tongue (the tenon)which pierces through a corresponding hole (themortice) in the other timberNAIL SICKNESSThe widespread failure of the nails holding roof slatesin placePARAPETThe part of a wall that rises above a roof or terracePARGINGThe application of lime mortar to the underside of rooffinishesPITCHThe slope of a roof; usually measured in degrees to thehorizontalPURLINA horizontal timber running parallel to the ridge andproviding support to the common raftersRAFTER (COMMON)A sloping timber roof beam running from eaves toridge and supporting the roof coveringRAFTER (JACK)A rafter shorter than the full slope from eaves to ridge,typically found at the hipped ends of a roofRELIGIOUS MARKSMarks made by a woodman or carpenter on timbers toappease the spirits. Not to be confused with assemblyor merchant marksRENDERA mixture of a binder (such as lime or cement), anaggregate and water to form a coarse plaster which isapplied to the external surfaces of wallsRIDGEThe longitudinal apex of a pitched roof. A ridge pieceor board is the longitudinal timber running along theridgeSARKINGTraditionally, timber boarding fixed above roof rafters,onto which the battens and counter battens werethen fixed. The term is now used for any flexible roofunderlay, including roofing feltSCARF JOINT OR SCARFINGA timber joint formed between two sections of timbercut diagonally so that they overlap and typicallyinterlockSCISSOR BEAMTwo interlocking timbers that cross in the shape of anopen pair of scissors, supporting rafters that have acommon apexSHINGLEA timber roof tile, usually of oak or cedar, sawn or cleftalong the grain of the timber. Also used as a wallcladdingSOAKERA small piece of flashing, approximately the size of aslate or tile, used to seal the joint at a valley or hip orbetween a pitched roof and an abutting wall such as agable parapet or a chimneystackSOFFITThe underside of any spanning or overhanging part ofa building such as the eaves of a roofSPROCKETA small timber attached to the upper face of a rafternear its foot to reduce the pitch of the roof over thewall head in order to slow down the flow of rainwaterand prevent it overshooting the gutterTIE BEAMThe bottom horizontal member of a roof truss, or atrussed rafter, tying together the feet of a pair of rafters107