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Glossary of Terms used in Trussed Rafter Construction
Room-in-the-Roof
See attic truss.
 
Scab
Additional timber fitted to the sides of a truss to effect a local reinforcement, particularly in raised tie trusses.
 
Setting Our Point
The point on a truss where the undersides of the rafter and ceiling tie meet.
 
Skew Nailing
A method of fixing trusses to the wallplate by driving nails at an angle through the truss into the wallplate which is generally not recommended. (See Truss Clip).
 
Soffit
Board fixed underneath eaves overhang along the length of the building to conceal timbers.
 
Span
Span over wallplates is the distance between the outside edges of the two supporting wallplates. This is usually the overall length of the ceiling tie.
 
Spandrel Panel
Atimber frame, triangular panel forming the gable wall above the ceiling line.
 
Splice
A joint between two members in line using a nailplate or glued finger joint.
 
Spreader Beam
See bearer.
 
Strap
Metal component designed to fix trusses and wallplates to walls.
 
Strut
Internal compression member connecting the third point and the quarter point on a Fink truss.
 
Stub End
See bobtail.
 
Temporary Bracing
An arrangement of diagonal loose timbers installed for safety during erection. Often incorporated with permanent stability and wind bracing structures.
 
Third Point
Point on the ceiling tie where the internal webs meet in a fink truss.
 
Timber Stress Grading
The classification of timber into different structural qualities based on strength (see BS4978: 1996).
Top Chord
See rafter.
 
TRADA Quality Assurance Scheme Quality control method in truss manufacture administered by the BM TRADA Certification.
 
Trimmer
A piece of timber used to frame around openings.
 
Truss/Trussed Rafter
A lightweight framework, generally but not always triangulated, placed at intervals of 600mm to support the roof. It is typically made from timber members of the same thickness, fastened together in one plane using nailplates or plywood gussets.
 
Trussed Rafter Designer
The person responsible for the design of the trussed rafter as a component and for specifying the points where bracing is required.
 
Truss Clip
A metal component designed to provide a safe structural connection of trusses to wallplates. Also to resist wind uplift and to prevent the damage caused by skew nailing.
 
Truss Shoe
A metal component designed to provide a structural connection and support for a truss to a girder or beam.
 
Uniformly Distributed Load
A load that is uniformly spread over the full length of the member.
 
Valley Board
A member raking from incoming ridge to corner in a valley construction.
 
Valley Frames/Set
Infill frames used to continue the roofline when roofs intersect.
 
Verge
The line where the trussed rafters meet the gable wall.
 
Wallplate
A timber member laid along the length of the load bearing walls to provide a level bearing and fixing for the trusses.
 
Webs
Timber members that connect the rafters and the ceiling tie together forming triangular patterns which transmit the forces between them.
 
Wind Bracing
An arrangement of additional timbers or other structural elements in the roof space, specially designed to transmit wind forces to suitable loadbearing walls.