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Trusses are used frequently in construction to support roofs on buildings. Classically in a triangle shape you can get trusses in a range of different types and styles.
When you are looking to use a truss it is important to have a structural engineer specify the section sizes to make sure that the trusses you want to use are suitable and will support your roof.
Closed trusses have a tie-beam connecting the two rafters. Normally the connection is at the bottom however you can also get trusses with a raised tie-beam where the tie-beam is elevated and connects the rafters further up.
A King Truss has a post running through the centre from the tie beam up to the truss’s apex. This post can either be straight or shaped and there are usually braces to help strengthen the truss however when there is a post, they are not always necessary (if you are unsure about anything with your truss please ask your structural engineer).
King post Trusses can be made into a mono truss which only has one rafter and a tie-beam which are connected by the king post and braces.
A Queen Truss doesn’t have a post but rather two braces for supporting the two rafters either side of the centre line.
You can’t make a mono queen truss because there is no post.
Open trusses are either scissor trusses or have a tie-beam with a gap which allows for a vaulted ceiling.
The principal rafters of Arch-Braced Trusses are connected by a collar beam which in turn is supported by two curved braces from underneath. You can get double arch braced trusses which have a second set of braces further down connecting the rafters to a block or sill.
Hammerbeam trusses have been developed to help span further distances with the largest distance spanned in England reported to be 20m. Hammerbeams have come about by taking arch-braced trusses further in development.
Scissor trusses look like a large pair of scissors. They have two principal rafters which are connected by two braces which dissect each other through to the other rafter.