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 Stairs and staircases

General criteria of stairs and staircases with attention to the third subject of national building regulations (4-4-1-3) and executive instruction of protecting buildings against fire (4-3-6) publication 112.
All the stairs which are to be located on the exit way, should have a fix and stable structure. The width of staircases and landings shouldn’t be decreased in any part of the path. Goings of all stairs are of the same type and same burnish and all necessary schemes for preventing slippery on the surfaces should be introduced.
Each staircase should have minimum of 110 centimeters as useful width. (Unless the number of the residents is below 50 people, en that case, the width of staircase will be decreased to minimum of 90 centimeter).
Each staircase should have minimum of 205 centimeter height to its ceiling and between the two consecutive landings should be the upright distance of 370 centimeters.
The rise of each stair should be maximum of 18 centimeters and minimum of 10 centimeters.
Each going of stairs should be minimum of 28 centimeters and has the ramp of maximum 2%.
The use of arcuate staircases on exit ways is allowed under these conditions :
A) Minimum size of going of each stair in distance of 30 centimeters from the narrowest part, should be 28 centimeters.
B) The radius of the smaller arc shouldn’t be less than double size of its width.
The use of spiral staircases staircases on exit ways, for maximum of 5 people, would be allowed under the conditions below:
A) The width of stairs shouldn’t be less than 65 centimeters.
B) The rise of each stair shouldn’t be more than 24 centimeters.
C) The useful height above the staircase shouldn’t be less than 200 centimeters.
D) The size of going of each stair in distance of 30 centimeters from the narrowest part of the stair, should be minimum of 20 centimeters.
The wide staircases should have, at least, a handrail for each 75 centimeters of their width.
Stairs protection
(۴-۴-۳) The inserted criteria below with attention to fourth subject of national building regulations
Height of handrails or ramp (inclined) shelters of stairs should be 90 centimeters from the edge of the stair.
Space between two consecutive balusters of railings shouldn’t be more than 11 centimeters. If the decorative railings are used, there shouldn’t be any kind of globs with the diameter of 11 centimeter passed in any part.

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