Pratt Truss Roof Details

This article and series of illustrated diagrams shows you all the parts of a basic roof truss king truss and queen truss.

Pratt truss roof details.

There are many types of roof trusses as wall as many types of roofs more types than there are parts. It offers a new alternative in prefabrication and field assembly methods without basic departures from established. The roof truss structure and design is integral to roof structural integrity and shape. These are very economical form of roof trusses.

These can vary a lot. This type of truss is used where gravity loads are predominant see below left. In a conventional pratt truss diagonal members are in tension for gravity loads. Flat truss with cantilever pratt configuration top chord bearing flat truss pratt configuration fl att rus w e nc of ig s l op i ngp are ch ds h w f u t sloping top chord howe configuration floor truss system 42 modified warren configuration mono trusses scissors mono mono parts of a truss framed roof gable end valley set gi rde.

This particular type of truss offers some interesting features mainly thanks to the fact that the vertical members provide tension while the diagonal ones are bringing in compression. Roof truss span tables alpine engineered products 15 top chord 2x4 2x6 2x6 2x4 2x6 2x6 2x4 2x6 2x6 2x4 2x6 2x6 bottom chord 2x4 2x4 2x6 2x4 2x4 2x6 2x4 2x4 2x6 2x4 2x4 2x6 2 12 24 24 33 27 27 37 31 31 43 33 33 46 2 5 12 29 29 39 33 33 45 37 38 52 39 40 55 3 12 34 34 46 37 39 53 40 44 60 43 46 64 3 5 12 39 39 53 41 44 61 44 50 65 47 52 70. Pratt truss pratt truss is made of steel. Better yet build your own pratt and howe truss bridges and compare their strength on your own.

A way of making a larger truss out of pre fabricated elements of smaller trusses these roof trusses are simple in design but very effective and cheap to build. However with most model bridges you are just using wood. Pratt truss this is one of the most popular steel roof truss types and it is quite economical. There are six main types of roof trusses as listed below.

Vertical members are tension and diagonal members are compression. The truss framed system tfs is a new light frame wood construction concept that inte grates customary construction components roof trusses floor trusses and wall studs into unitized frames. It used wood for the vertical members. I think this does give the pratt an advantage but read my best bridge design article more for information.

Pratt trusses are commonly used in long span buildings ranging from 20 to 100 m in span. The ones in the photo above are in a heritage building of around the 1950 s fannie bay gaol darwin nt. For further details on how the loads are calculated on a truss and other design details please read this. It can be used for spans from 6 10m.