The rafters are important structural elements in both the purlin and rafter roof. However, depending on the respective roof structure, there are significant differences in the load on the rafters. In the following we will not only show you the respective advantages and disadvantages, you will also find further information on rafters.
Origin of the designation rafters
The term "rafter " has its origin in Middle High German in the times of the Middle Ages. This shows how important rafters have always been for roof structures, explicitly north of the Alps. The word is something to be equated with splayed or upright beams - just like rafters are built in.
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There are rafters here
You can find rafters on various roof structures. The two most important types of roof trusses in German-speaking countries are the following.
- Purlin roof structure
- Rafter roof truss
Duties of the rafters
Both roof trusses can also be combined with each other. The importance of the rafters is subordinate to the purlin roof. With a rafter roof, on the other hand, it is the rafters that dissipate the entire weight. The weight that the rafters have to divert is made up of several factors.
- Dead weight of the rafters
- Roof cladding (e.g. concrete or tile roofing tiles)
- Snow, rain, wind
Rafters on the purlin roof
In the purlin roof structure, the rafters transfer the weight directly onto the purlins, which in turn transfer it to the building ceiling via the supports. From there it is diverted via the facade and load-bearing walls. This means that a particularly difficult substructure is not necessary with the purlin roof.
Rafters on the rafter roof
However, it looks different with the rafter roof. All weight is diverted here via the rafter foot. However, these forces also have an external effect. In order to be able to absorb this enormous tensile force without problems, a difficult jamb construction has to be integrated between the building ceiling and the rafter roof.
Rafters: insulation is used here
The transverse battens are now attached to the rafters themselves. This is installed with the roof cladding for later covering. Depending on whether the technical roof design is a warm or cold roof, there is also insulation in between. The insulation of the roof truss is also differentiated according to the position.
- Above-rafter insulation (outside)
- Between-rafter insulation (from the outside, but often from the inside)
- Above or below rafter insulation (from the inside)
Rafters and EnEV
Over the next few years, insulation between rafters and rafters from the inside will be particularly important for existing buildings. Because according to the EnEV (Energy Saving Ordinance), many homeowners are gradually forced to insulate their roof structure accordingly. This is the case, for example, if you buy an existing building without existing insulation according to the EnEV.
Insulate the roof structure efficiently
Insulation between and above rafters from the inside is then often the only inexpensive option to comply with this insulation. In the case of between-rafter insulation, clamping felt mats are clamped between the rafters. With over-rafter insulation, they are attached to it. Combinations are of course also possible.
Maintenance of the roof structure including the rafters
With all these aspects, the rafters of a roof truss keep coming into the focus of a homeowner. In addition, as a homeowner, you shouldn't forget that the rafters, like the entire roof structure, require regular maintenance. This is the only way to identify damage caused by moisture or pests in good time and to prevent high follow-up costs.Tips & Tricks In the house journal we offer you numerous articles, advice and instructions on a wide variety of roof-related topics. For example, for the purlin roof.