Roof Trusses

 

Aisled Barn

A type of roof truss construction that has aisles down the side to increase the span

Arcade post

A post at the side of a cruck truss to share the load and shorten the span. Usually seen in pairs in aisle barn construction.

Arched brace

A curved brace, normally out of naturally curved timbers used to stiffen a roof frame. Usually in pairs.

Base cruck

The cruck blades sit at ground level and rase to be joined to a tie or collar beam.

Belfast truss

A roof truss that has the top chord in the form of a circular or sometimes a parabolic arc. Known to be economical over large spans.

Belgian truss

Similar to a W truss or a Warren truss for longer spans with extra webs added. Also called a double Fink truss

Bowstring truss

A roof truss that has the top chord in the form of a circular or sometimes a parabolic arc. Know to be economical over large spans.

Buttress

A mass of masonry bonded to an exterior wall. Usually to stiffen it against the lateral thrust of roof structures.

Cambered Fink or Cambered Warren truss

A Fink or Warren truss with a raised center bottom chord.

Cantilever truss

A truss where one end is allowed to run over the support. Part of the truss is said to be a cantilever.

Cruck blade

A single piece of timber when paired with another similar piece becomes a full cruck frame.

Cruck construction

A category of medieval architecture of unsure origin where the main load bearing members are crucks. Large section naturally bent timbers that reach from the height of the roof to the floors. Later they extended to low side walls.

Cruck Truss

1.) One of a pair or naturally curved timbers used to form frames or trusses that were the main structural elements in medieval building in Northern Europe.
2.) A building that contains crucks or built using crucks.

Dendrochronology

In old timber framed buildings it is used to date the time that trees were felled, and so the construction date, by various methods including study of the annual growth rings and carbon dating.

Dendrology

The branch of botany involving the study of trees and shrubs.

Eltham Palace Roof

The third largest example of a hammer beam roof in the UK, built to cover the great hall of the palace built for Edward 1V in the 15th century south of London.

Fan truss

Similar to a W truss but with extra vertical ties added. Said that each sides web radiate like a fan.

Full Cruck

A cruck frame which reaches from the ridge to the floor using none jointed blades.

Gang nail truss

One of a series of trusses made with light timber sections joined together with metal nail plates.

Girder truss

A roof truss that acts a truss, but at the same time is built stronger than a standard truss of the same span to carry extra loads imposed on it. Used in nailplate truss construction. Sometimes consists of two or more standard trusses fixed together.

Half truss

Used in shed type roofs and lean to roofs, it is in effect half of a normal truss with a vertical member to complete the triangle.

Hammer Beam Truss

The ultimate development of timber roof truss design before the advent of modern materials, the hammer beam truss uses hammer beams extending a short way out from the walls to create an open and usually a highly decorative effect. The hammer beam roof is a peculiarly English creation with the finest example being in Westminster Hall.

Hampton Court Palace Roof

The second largest example of a hammer beam roof in the UK, built to cover the great hall of Henry V111’s Tudor Palace at Hampton Court on the banks of the Thames near London, UK

Hip truss

One of a series of trusses made with light timber sections joined together with metal nail plates that sits in the hip position.

Howe girder

A girder or truss with horizontal chords and the diagonal members pointing down and towards the supports.

Howe truss

A roof truss with vertical web members to take tension forces and with angled braces to take compression

Iron Roof Truss

A roof truss made out of either wrought iron, cast iron or more likely a combination or the two. Capable of large spans and often highly decorated.

Jack truss

Used in nail plate truss construction, a subsidiary truss that is fixed to a truncated truss with it’s top chord flying over to reach the hip. Where not fixed to a truncated truss it is fixed to a hip truss.

Jointed cruck

A cruck with joints to the main members. To extend the length of the timbers or alter the shapes.

King post truss

A roof truss mostly wooden with two principal rafters, a tie beam and a central vertical King post. The simplest of trusses. Mainly used with two angled struts.

Knee brace

A brace between a post and beam, the bottom chord of a roof truss and the support, or a stiffener in a portal frame.

Monospace truss

Used in shed type roofs and lean to roofs, it is in effect half of a normal truss with a vertical member to complete the triangle. The strut and web pattern is the same as a W truss.

Pratt girder

A girder or truss with horizontal chords and the diagonal members pointing down and towards the center.

Pratt truss

A truss with alternate vertical and angled members between the chords. They angled members pointing down and towards the center.

Principal rafter

One of the main diagonal members in in a roof truss on which the purlins sit, which in turn support the common rafters.

Queen post truss

A roof truss mostly wooden with two principal rafters and two vertical Queen posts with a restraining tie beam at the bottom and a straining beam at the top.

Raised cruck

A cruck truss that is raised to sit on usually short walls. Either masonry or timber.

Reducing truss

One of a set of nailplate roof trusses that sit on the backs of other trusses to form valleys.

Sailover truss

A truss where each end cantilevers over the support. Used to get extra height at the wall plate or to simplify boxing in the eaves.

Scissor truss

A truss with both the top chords and the bottom chords sloping upwards. To give a greater ceiling or clearance height.

Straining beam

1.) In a truss a horizontal strut above the tie beam.
2.) In a queen post truss the horizontal strut between the ends of the queen posts.

Straining sill

A horizontal member in a timber roof, typically fixed to a tie beam to resist the sidways thrust of struts.

Tie beam

1.) A horizontal member in roof framing, fixed to the foot of rafters to stop them spreading.
2.) In truss construction, timber or steel, the bottom horizontal member. The bottom chord.

Tie Rod Truss

A roof truss that uses tie rods for the members under tension, ties, and solid timber or metal for the compression members.

Truncated truss

A standard truss that has been truncated or has had it’s top cut off. Usually to allow jack trusses to pass over it in hip roof design. The term girder truss truss is commonly applied as these trusses ofter act as a girder supporting the minor trusses abutting it.

Upper cruck

The upper blades are sat on a tie beam and raise up to the ridge.

W truss

A triangular truss where the web members take the form of a W.

Warren girder or Parallel chord truss

Parallel top and bottom chords joined by any number of W webs.

Wattle and Daub.

A method of building walls using interlaced thin lathes or branches (wattles) that are roughly plastered over with clay (daub) typically as infill panels between timber framing.

Westminster Hall Roof

The oldest and largest example of hammer beam roof, built to cover the large hall of Westminster Palace in London.