The roof truss - the supporting element in building a house

The roof truss serves as a supporting structure and carries the covering of the house. For centuries, the construction of the roof truss has been further developed and refined. In a residential building, the roof truss is usually made of wood.

Supporting structure and roof shape

The roof shape and roof truss must harmonize with each other. This not only means the shape of the roof truss, but also the strength of the elements used.

For example, the rafters not only have to be strong enough to secure the roof battens and roofing even during storms and heavy snowfall. The rafters must also be strong enough to withstand the insulation that is needed for an energy efficient house today.

Individual technical terms

Of course, nobody has to do an apprenticeship as a carpenter before building a house. But some terms should already be known to one's own roof truss. So you can better judge the individual elements that are to be installed.


Between eaves and ridge the rafter is set up. The rafter determines by its length in relation to the size of the roof truss, both the roof pitch and at the same time the roof shape. With a pitched roof, the rafters are set up, for example, in pairs. On the rafters, the roof battens are fixed, which then carries the roofing.


Throat bars are inserted horizontally between a pair of rafters. As a result, the rafters support each other in large roofs. If the throats were missing, the rafters would have to be much larger.


When purlin roof, all three types of purlins can be installed as well as only one of the purlins. The purlins support the rafters.

eave plate

The Fußpfette lies on the outer wall of the long side and carries at the lower end the load of the rafters.


The middle purlin supports the rafters horizontally in about the middle of the rafter length.

ridge beam

As the name implies, the ridge purlin runs between the two upper ends of the rafter pairs at the ridge and carries the weight of the rafter ends.


The battens are nailed horizontally parallel to the rafters from the outside. They hold the roofing and secure the rafters against slipping. Their strength only has to be matched to the weight of the covering.

wind brace

The Windrispe is stretched either as a strong board or as Windrispenband between the Fußpfette and the ridge purlin obliquely. It is attached to each rafter on their way and secures them against slipping sideways.

chair post

When installing chair posts, they are usually under the throat bars to support them. If a pillar is used to support the mandril, it is a simple standing chair. In a double-standing chair, the chair posts are on the sides at the level of the middle purlin.

Trusses - different designs

There are some basic forms of trusses, which are usually made of wood. However, many different forms of mixing are common, which have become established over time. Here are the main roof trusses

  • Simple rafter roof chair
  • Collar beam roof
  • purlin
  • Mansarddachstuhl
  • Truss roof
  • Truss roof

Simple rafter roof chair

A simple rafter roof chair is conceivable as a gable roof or as a pent roof, for example. Here is on both throat bar and on purlins omitted. In the case of the saddle roof, the rafters of the simple rafter roof are placed in pairs against each other and thus form a thought triangle on the floor below.

Collar beam roof

The Kehlbalkendachstuhl is a rafter roof chair with a supplement by Kehlbalken, which are inserted horizontally between the rafters. At the same time, the throat beam layer usually forms the interior construction of the false ceiling between the developed rooms in the attic and a pointed floor that lies above.

If the throat bar is used in a purlin roof, it should spread the two middle purlins and thereby additionally stabilize. At the same time, the position of the individual throats also forms the floor of the floor above and the ceiling for the floor below.

This is one of the mentioned popular mixed forms, which are often used in trusses. Here elements of the rafter roof with a purlin roof and the Kehlbalkendachstuhl are constructed together to a durable roof truss.


For most purlin roofs, all three types of purlins, together with a rafter roof, are turned into a very robust roof truss. This form of roof truss is very common in hipped roofs or very tall pitched roofs that are built in windy areas.


A mansard roof chair looks like a pitched roof that changes its roof pitch on the roof surface. Due to the almost very steep sides of the mansard roof oblique elements account almost completely. So you get a living room in the attic, which offers almost the same square foot size, as the underlying floor.

Disadvantages are, of course, the more complicated design and the difficult sealing. For the steep sides special roof tiles must be selected, which nevertheless protect the interior from any moisture at this strong inclination.

In addition, several roof windows must provide light, which is usually more expensive than if a conventional window can be installed.

Truss roof

The suspended roof structure works basically like a suspension bridge. A suspended post carries the roof areas in the middle of the simple suspended roof truss. In the case of a double suspension, the load is distributed over two posts, which are secured and connected with the tension bar and strut.

Truss roof

In the case of a truss roof truss, the load is caught in oblique struts. So the living space under the roof can be significantly larger, because no restrictive vertical struts must be set up.

The oblique struts are usually used directly under the slope, which allows just the full usability of the base. In addition, dividers can be placed where you want and not where the support beams in the way.

As well as the suspension, the explosive device is used in bridge construction and offers similar advantages there as in a roof truss. There is also a practical combination of the two types of roof truss for the suspended roof truss and the roof of the roof.

Tips & Tricks

Stay true to traditional trusses when building your own home. This is not only cheaper, because the constructions have been tried and tested for centuries. If you would like something out of the ordinary, do it with a special glaze or paint. For private homes, rafter roofs or combinations of rafters, purlins, and fillet bars are by far the most practical solution. These trusses are also very robust and stable for many decades.

Video Board: Simple Explanation About Roof Truss Design, Parts And Assembly