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The attic framing is the top framing.
It supports the roof structure.
All partition walls and the centre wall are ending beneath the attic framing. Fire walls, however, extend until beneath the roofing.
Because the attic framing supports the roof structure, the wooden beams of this framing may have different widths. They all should, however, have the same height!
Why should all wooden beams of the attic framing have the same height?
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For equidistant distribution of the beams it is important that the joining beams should not exceed a distance of 4000 mm.
What purpose do the joining beams serve in the attic framing?
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It is recommended to fix the location of the joining beams and then to calculate the pitch size for the intermediate beams between them.
Figure 10
Pitch size between joining beams
1 joining beam, 2 intermediate beam, 3 wall plate, b1, b2 width of wooden beams, T pitch size, Lr arithmetical length for pitch size calculation
The pitch size can be calculated to formula (1) in section 5 hereof. In addition to the floor mark and a number, the joining beams also have a marking-out mark.
Figure 11
Wooden beams marked with floor mark, jointing mark, number and marking-out marks
1 intermediate beam, 2 joining beam, 3 wall plate, 4 inner or
centre wall, 5 outer wall
a marking-out mark for
straight tenons, b marking-out mark for angular tenons, c void
mark
Why do the wooden beams of a framing have a number and a floor mark?
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What are marking-out marks?
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The collar-beam framing is no typical wooden beam framing. It is mainly applied in a rafter roof. The purpose of the collar beams is to stiffen the rafter pair of a rafter roof.
But collar beams may also be built into a purlin roof when the roof room is very high and shall be used effectively.
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