The purlins

Purlins are an important part of the roof or truss, as they not only carry the weight of the roof, but also derive it. The importance of purlins derives from the origin of the word. Traditionally, purlins consisted of wood, but today also other materials are used. Below you will learn a lot of interesting facts, but also advantages and disadvantages as well as statements on the cost of purlins.

Purlins have a long tradition of roof construction

It is not completely clear where the word "purlin" comes from in the end. However, both options go back to very old terms, which already provides information about how important purlins have always been and still are in roof and roof construction. One possible origin is the Latin "Patena" or "Patina", which can mean as much as basket, but also layer or thin layer. The second alternative comes from the gothic wedding, around 1100.

The dressing of the roof

Here is the word "Pfeit", which derives from "Paida" and means something like a shirt or a smock. Also at that time the term for the "undressing", the "Enpfetten", was in common use. Whatever the true origin of the word "purlin", it is clear that it has existed for many centuries.

The purlins: roof

Construction of a purlin roof chair

As a rule, the purlin runs parallel to the eaves or the ridge. Here, purlins are used at different heights of the roof truss.

  • the ridge purlin
  • the middle purlin
  • the foot purpins

The ridge purlin, as the name implies, forms the upper end of the roof truss at the level of the ridge. Half way to the attic foot comes the middle purlin, whose position also follows the statically calculated peculiarities. The truss is then completed by the Fußpfette. The can either rest on the ceiling of the underlying projectile and be designed as a ring beam, or it is attached to the knee stick or Drempel (also Trempel).

The purlin roof faces the rafter roof

The rafters are now attached to the purlins in order to cover the roof. But purlins are not always necessary. Especially in northern Germany steep roofs prevailed due to the weather conditions (lots of rain and wind). They can carry the roof skin more efficiently and better sealing than a pure rafter roof.

The problem of the rafter roof chair compared to the construction with purlins

The weight is no longer derived from purlins. Rather, the rafters of both halves of the roof support each other and derive the pressure and the weight at their feet. Therefore, a rafter roof needs a special (Drempel-) construction to safely derive these particularly strong forces can.

Purlins for larger areas and even roofs

On the other hand, the purlins can take over the tasks of the rafters, making them superfluous. This is mainly used for cold roof flat roof constructions. This special purlin shape is called as Sparrenpfette or purlin sparrow, as well as coupled purlins is right.

Advantages and disadvantages of the roof structure with purlins (Pfettendachstuhl)

The pros and cons of purlins should not be related to the individual purlin. Rather, it is the construction of the purlin roof or Pfettendachstuhl that forms the corresponding advantages or disadvantages.

Advantages of the purlin roof

  • Even large, very wide roofs can be realized
  • The weight is well controlled via the support beams
  • the flatter the purlin roof, the cheaper the construction
  • Low space loss due to possible flat roof pitches
  • no complicated and expensive to construct knee skirt

The disadvantages of the purlin roof

Of course, the disadvantages can be deduced exactly from these advantages.

  • To support the roof load support beams are required, which must derive the weight mandatory on underlying load-bearing walls
  • the steeper the purlin roof, the higher the wood consumption

Costs at the purlin roof

As is often the case with Pfettendach, concrete statements about the costs can not be made. As you can see from the advantages and disadvantages, for example, increases the need for material or wood (in a wooden roof truss and other materials, because the purlin roof chair can also be made of steel).

Many factors play a role in the Pfettendachkosten

Added to this is the need for supporting walls, which must be designed accordingly and, moreover, have a strong influence on the floor plan of the entire building in terms of spatial planning. Basically, if you plan to make economic sense, you should assume that the roof covering as well as the construction of the purlin roof chair are at least 45 to 70 euros per square meter.

Tips & Tricks

Do not save in the wrong place with the Pfettendachstuhl. Of course, the price is important, but you should use the price rather secondarily. There are "companies" that show themselves on the Internet more and more often or draw attention to themselves by throwing mail without coming from their own region. Often come here incredibly "cheap" prices from 30 euros. But quickly the alleged bargain becomes a cost trap, because everything has to be renewed or strengthened after a short time.

If you really want to save money, you can build your own Pfettendachstuhl or at least help. Already from the setting of the roof truss there are producers who make this possible for you. You can often choose to support the professional crafts team or hire a carpenter under the supervision of which you work. For example, under the setting of the roof truss and the adjoining truss construction, you will also find numerous articles on the Pfettendachstuhl in the Lets-ReBuild.com.

Video Board: DIY ROOF: WHAT ARE PURLINS??