Manufacture of Ceilings - Course: Timberwork techniques. Trainees' handbook of lessons (Institut für Berufliche Entwicklung, 22 p.) |

The wooden beams of a wooden beam ceiling should be placed at equal distances so as to equally distribute the load on all beams.

If the distances between the wooden beams are not shown in the drawing, the pitch size is to be calculated.

**Figure 12**

Determination of the pitch size

(1) bay 1, (2) bay 2, (3) bay 3

*Lr** length required for the calculation,
BL length of wooden beam, T pitch size (beam spacing), B clear
width of the room, L length to be distributed, a bearing length,
b_{1}, b_{2} width of wooden beams, c minimum
distance of wooden beams from the wall, 1, 2, 3, 4 wooden beams*

The pitch size depends on the thickness of the flooring and is calculated to formula (1).

_{}

T = pitch size (distance of wooden beams)

L_{r}= length required for the calculation

n_{F}= number of bays

The number of bays is determined by means of formula (2).

_{}

T_{zul}= pitch size depending on the thickness of the flooring

20 mm thick flooring - - - pitch size T_{zul}= 600 mm

24 mm thick flooring - - - pitch size T_{zul}= 800 mm

30 mm thick flooring - - - pitch size T_{zul}= 1000 mm

If the resulting n_{F}is a decimal fraction, it is to be rounded off to bring it up to the next integer number.

The rounded-off number of bays is provided with a superscript mark for identification.

For example: n_{F} = 6.4; __n’ _{F} = 7__

The length to be distributed is determined by deducting the wooden beams’ minimum distance from the wall at both ends from the clear width of the room.

L= B - 2c (3)

L = length to be distributed

B = clear width of the room

c = minimum distance of the wooden beams from the wall, normally 20 mm

For the calculation of the pitch size, the arithmetical length is required. It results from formula (4):

_{}

b = wooden beam width

Formula (5) gives the number of wooden beams to be placed over a calculated distance:

n_{B }= n’_{F }+ 1 (5)

The length of the wooden beams is calculated to formula (6):

BL = w + 2a (6)

BL = length of wooden beamw = clear width of the room

(in straining direction of the beams)

a = bearing length

(a = at least 150 mm)

Why should the wooden beams have equal distances?

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Why should the wooden beams have equal distances?

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Why must the wooden beams have a distance of a least 20 mm from the wall?

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What does the formula n_{B} = n’_{F} + 1
say?

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Why must n_{F} be rounded off to the next integer
number?

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