Rafter purlin

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Sketch of a hall. green: roof trusses , black: rafter purlins as coupling purlins

The rafter purlin (rarely also purlin rafters ) is the load-bearing component of the roof structure , which, like an ordinary purlin, lies parallel to the eaves. Rafter purlins are so close together that the rafter layer usually following above can be omitted. In this respect, they also take on the function of the rafters and the purlins.

Rafter purlins have in common with the battens of a traditional roof that both run horizontally and often form the top level of the roof structure, on which the roofing lies directly . In contrast to roof battens, rafter purlins have a much larger cross-section, as they span larger spans and are usually laid with greater spacing. Trapezoidal sheets are often laid on rafter purlins , which, depending on the height of the profile, can span well over a meter.

Rafter purlins lie on girders (today mostly made of steel or glued laminated timber ) and are usually made of wood or steel. The main areas of application are flat roofs and hall roofs .

On the sloping roof , they are subjected to double bending when the forces in the y-direction are not taken over by the roof membrane acting as a pane.

Tile-covered pitched roofs on residential buildings are usually not realized in the German-speaking area with rafter purlins, but with the classic construction with rafters , which are supported by the purlins below.

Rafter purlins are usually only used when no horizontal battens are required. For example at:

In the Mediterranean region, it was customary to cover closely spaced purlins made of round timber with hourdis panels, on which mortared monk and nun tiles form the roof membrane.

In Scandinavia there is the so-called carrion roof with closely spaced purlins that directly support the roof skin.

species

  • Single-span rafter purlin
  • Continuous rafter purlin (without joints)
  • Articulated purlin ( Gerber beam )
  • Coupling purlin (coupling beam)

swell

  • Otto W. Wetzell (Ed.), Wendehorst - Structural number tables , Beuth Verlag Berlin