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Before you can start to calculate the pitch size, you have to check the perpendicularity of the walls, the horizontal of the ceiling and of the floor, the squareness of ceiling and wall and of floor and wall.
Any deviations are to be considered in the calculation of the pitch size.
For example, the distance between the wall post and the following or preceding post may be different at the head runner or foot runner.
The post at the right hand of the left wall post and the post at the left hand of the right wall post must be perpendicular.
The joint post should have a width (b) of at least 80 mm to provide a sufficient bearing surface for the surface covering material.
The width of the joint post is not taken into account when calculating the pitch size (distance of the posts from jointing to jointing). The difference of the joint post width is determined when scribing on the runners.
Figure 15
1 runner, 2 pitch size, 3 post width, 4 compensated joint post width, 5 jointing mark
The calculation of the pitch size is based on a symmetrical arrangement of the framework of the partition wall and is done as follows:
In the event of one joint post between the wall posts or between the wall post and the corner post:
- Read the dimensions for the posts to be used to know the width (b) of the post for the calculation!(If posts of other width are used, take that width for the calculation).
- Divide the total length of the partition wall (G1) by the length of the covering material to be used (M1)!
The result gives the number of sections (nT).
Formula:
If nT is a decimal fraction, round up to the next integer number!Subindex “a” is then added to nT (nTa)!
- Divide the total length (G1) by the rounded-up number of sections (nTa)!The result gives the length of one section (Lt).
Formula:
- Subtract half the width (b/2) of the post to be used from the length of the section (Lt) and divide by the admissible distance of the post (aadm)!The result gives the number of divisions of one section (nF).
Formula:
If nF is a decimal fraction, round up to the next integer number!
Subindex “a” is then added to nF (nFa)
- Divide the length Lt - b/2 by the rounded-up number of divisions (nFa)!
The result gives the distance of the posts (a) between the wall post and joint post or wall post and corner post.
Formula:
If “a” includes tenths of a millimetre, they are compensated when scribing!
Several joint posts in the framework of the partition wall
If several joint posts are required between the wall posts or between the wall and corner posts, then do not subtract half the width of the post from the section as explained in step 5 above!
Formula:
Example 1:
It is assumed that the partition wall to be built has a total length of 4000 mm and the height of the room is 2750 mm. The length of the covering material is 2200 mm. The distance of the posts must not exceed 500 mm!
What pitch size is to be scribed on the runners?
Solution:
1. Reading of the dimensions of the posts in table 1.
b = 50 mm, d = 78 mm or b = 55 mm, d = 75 mm or
b = 60 mm, d = 72 mm or b = 65 mm, d = 69 mm or
b = 70 mm, d = 63 mm or b = 75 mm, d = 61 mmDecision in favour of b = 50 mm, d = 78 mm.
2. Calculation of the number of sections.
Requ.: nT 
Known: G1 = 4000 mm
M1 = 2200 mm
nTa = 2
3. Calculation of the number of sections.
Requ.: Lt 
Known: G1 = 4000 mm
nTa = 2Lt = (4000 mm)/2
Lt = 2000 mm
4. Calculation of the number of divisions: “Two sections” means one joint post!
Requ.: nF 
Known: Lt = 2000 mm
b =50 mmaadm = 500 mm
nFa = 4
5. Calculation of the pitch size:
Requ.: a 
Known: Lt = 2000 mm
b = 50 mmnFa = 4
a = 493.75 mm
Result:
The pitch size to be scribed on the runners for the posts to be mortised amounts to 493.75 mm from jointing to jointing.
When scribing the pitch size on the runners, the folding rule is to be placed so as to permit continuous scribing:
493.75 (+493.75 =) 987.5 (+493.75 =) 1481.25 (+493.75 =) 1975
Figure 16
Example 2:
It is assumed that the partition wall to be built has a total length of 7860 mm. The room height is 2500 mm.
The distance between the posts must not exceed 400 mm.
The covering material has a length of 2000 mm.
What pitch sizes are to be scribed on the runners?
Solution:
1. Reading of the dimensions of the posts in table 1:
Selected: b = 60 mm, d = 68 mm
2. Calculation of the number of sections:
Requ.: nT
Known: G1 = 7860 mm
M1 = 2000 mm
nTa = 4
3. Calculation of the section length:
Requ.: Lt
Known: G1 = 7860 mm
nTa = 4
Lt = (7860 mm)/4
Lt = 1965 mm
4. Calculation of the number of division:
Requ.: nF 
Known: Lt = 1965 mm
b =60 mm
aadm = 400 mm
nFa = 5
5. Calculation of the pitch sizes:
For section A - D
Requ.: a
Known: Lt = 1965 mm
b = 60 mm
nFa = 5
a = 387 mm
For section B - C
Requ.: a 
Known: Lt = 1965 mm
nFa = 5
a = 393 mm
Figure
17
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