Clarke CONTRACTOR 6462120 Operation & Maintenance Instructions Manual - Page 5
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Going
The going of a step is the space between the nosing of one step and the nosing of the
step above - or as British Standards state, face of a riser to face of a riser. Like the riser,
British Standards state strict regulations. These are - The going should not be less than
220mm for a private stairway and not less than 250mm for a common stairway.
Pitch line
The pitch line is an imaginary line, which is drawn from the edge of each tread. It stretches
from the floor to the landing.
Pitch
The pitch is the angle between the imaginary pitch line and the horizontal of the tread.
(See diagram). Regulations state that this should not exceed 42º for a private stairway
and 38º for a common stairway. The pitch should never be less than 25º because a stairway
with a shallow angle takes up more room than those with a deeper angle.
Margin
The margin is the distance between the imaginary pitch line and the edge of the string.
Going
String
Rise
Pitch Xº
Riser
Pitch Line
Margin
Nosing
Tread
Planning your staircase
The first information that you will need to find out is the total rise of the flight and the
total going of the flight, if this is restricted. The normal rise of a step is between 170mm
and 200mm. Therefore, divide the total rise by say 180.
For example, If the total rise of a flight is 2405mm and we have assumed that 180mm is
your chosen rise, calculate the exact size as follows;
2405 = 13.36
180
Round off to the nearest decimal point, this example = 13.
You will therefore need 13 steps (13 risers) 2405 = the size (185mm) of each rise.
13
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