Purlin roof

Purlin roof as a saddle roof with ridge purlin, two central and two foot purlins. Often necessary stems are not shown .

Purlin roof with traditional natural stone cover in Val Lavizzara

The purlin roof is one of the traditional roof constructions for making a pitched roof . Its name-giving main feature are the horizontal purlins on which the sloping rafters rest.

The rafter roof , or rather the collar beam roof as a special form of the rafter roof , pursues another construction principle .

history

The historic purlin roof comes from the Mediterranean area and was originally a flat roof . The rafter and collar beam roof , on the other hand, are considered to be the oldest forms of roof construction in Central and Northern Europe ; in the course of the 19th century they were replaced in Germany by the purlin roof. Today the purlin roof is the dominant construction principle for pitched roofs. It enables larger rafter lengths and thus the implementation of larger roof structures than the rafter roof.

construction

The purlin roof consists of several rafters staggered one behind the other across the direction of the ridge , which are also referred to here as Rofen . These rest on the purlins , which transfer the loads downwards. In the case of wooden purlin roofs, this is usually done by means of a claw : a 2 to 4 cm deep claw (or mouthpiece) in the rafter ensures a hold on the purlin. A rafter nail is used as additional security in traditional constructions . Today, so-called rafter purlin anchors also exist as wood connectors.

In the case of the purlin roof, the rafters on the opposite roof surfaces (rafter layers) can also be offset - unlike with the rafter roof. A matching pair of rafters is not required. In this respect, the purlin roof is not only suitable for the construction of pitched roofs, but also for pent roofs . The monopitch roof is also regarded as the original form of the purlin structure, the purlin roof as a gable roof is in this respect the combination of two monopitch roofs with a common ridge purlin.

advantages and disadvantages

In timber construction , the purlin roof has both advantages and disadvantages compared to rafter and collar beam roofs .

The advantages are:

• Small horizontal forces , therefore no complex jamb structures necessary in the eaves area .
• The erection of large dormer windows does not cause any difficulties.
• Hip constructions are problem-free.
• Favorable wood consumption with small roof pitches .
• Simple cutting and assembly.

The disadvantages are:

• In the roof space are stems (and head bands ) or Maue slider rest necessary, the roof space is so far not clear.
• Leg loads must be absorbed by the ceiling of the floor below.
• Greater wood consumption with a greater roof pitch.

References and footnotes

1. ↑ Composition based on Hagen Prehl: Wooden roof structures , 2nd edition, Düsseldorf, 2001, Werner Verlag, p. 29.
2. ↑ Set after Hagen Prehl: Wooden roof structures , 2nd edition, Düsseldorf, 2001, Werner Verlag, pp. 18 and 19.
3. ↑ Sentence based on Hans-Jürgen Sterly: Kehlen im Ziegeldach , 1984, R. Müller, p. 26.
4. ↑ List based on Hagen Prehl: Wooden roof structures , 2nd edition, Düsseldorf, 2001, Werner Verlag, pp. 29 and 30.
5. ↑ List based on Hagen Prehl: Wooden roof structures , 2nd edition, Düsseldorf, 2001, Werner Verlag, pp. 29 and 30.