The rafter roof

The rafter roof is the traditional roof of Central and Northern Europe. However, it also limits the possibilities of roof designs and additional elements such as dormers or skylights. Nevertheless, it has advantages that make it attractive to other roof structures. Below you will learn everything about the rafter roof.

Construction of a rafter roof

In the rafter roof chair, the rafters of the two sides of the roof run towards each other from the bottom to the top, supporting each other as it were. The weight of the entire roof truss along with the roof skin is derived from the rafters. Thus enormous horizontal forces act in the foot area of ​​the rafters, which makes a particularly massive substructure necessary.

Important element: the knee stick or drumming

This substructure is a Drempelkonstruktion (knee stick), it is traditionally attached to a circumferential ring beam, which in turn is connected to the rafter roof. The correct and competent execution of the Drempelkonstruktion is crucially one of the most important elements of the rafter roof construction.

The rafter roof: roof

Rafter roofs are preferably built from 30 degrees

The flatter a rafter roof, the more complicated the static. Therefore, rafter roof chairs are usually designed from a roof pitch of 30 degrees and more, so they can be found especially in very steep roofs. This results in very special advantages.

The advantages of the rafter roof

  • more living space in the attic due to the steep rafters
  • the weight is completely discharged via the ring beam on the knee skirt, there are no disturbing support beams
  • The wood consumption for a rafter roof chair is relatively low

Probably the most significant advantage is the fact that no disturbing support beams can be found on the entire floor plan. This not only gives a free and well planable attic area. Depending on the rest of the house construction, there are no load-bearing walls that run through the floor plan, as the weight is dissipated via the outer walls.

The disadvantages of rafter roof

But it is precisely these advantages that also bring very specific disadvantages.

  • The rafters of each half of the roof must be facing each other
  • because the rafters alone derive the weight, recesses for dormers and skylights are only partially possible
  • House widths (depth) are limited to a maximum of 8 to 9 m
  • Hedgehog constructions are very difficult to realize

Special forms of rafter roof chair

The drawback of the building depth can be circumvented somewhat by planning a Kehlbalkendachstuhl instead of the pure rafter roof. The Kehlbalkendachstuhl is also a rafter roof, but the opposite bars are connected at half to 1/3 height by crossbars - the throat bar - with each other. As a result, wider Kehlbalkendach versions are feasible.

Additional advantages as Kehlbalkendach

In addition, the throat bars can also be designed as double pliers. Often, the fillet bars in this special form of rafter roof have other advantages: you can use the fillet bars as the backbone for your attic floor extension.

alternatives

Some of the above problems and disadvantages can be neutralized by combination roof chairs. For example, if you connect a purlin and a rafter roof chair with each other.

Tips & Tricks

Especially after the Second World War, the rafter roof chair was considered the measure of modern house construction. So it is not surprising that a massive proportion of houses with rafter or Kehlbalkendachstuhl accounts for the first post-war decades.

Of course, in the house journal you will also find plenty of information about other trusses such as the Pfettendachstuhl.

Video Board: DIY ROOF: RAFTER'S BIRD MOUTHS