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Author Topic: stair widths when calculating occupancy levels  (Read 162 times)
paul1969
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Posts: 14


« on: December 02, 2017, 11:00:53 AM »

If lobby doors leading to a protected stairway are 1200mm, but the stairway is 1000mm, which figure should be used for calculating max. occupancy capacity when using BS9999?

Risk profile of building is A2.

Building designers have used the door width in the plans to calculate the floor level capacity.  But should it be the lowest figure??
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Mr. P
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Posts: 685


« Reply #1 on: December 06, 2017, 11:47:31 AM »

69ers, if occupancy numbers are maxed out by you using the door width, there's a chance the corridor could clog up or someone gets pushed down the stairs...
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SeaBass
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Posts: 147


« Reply #2 on: December 06, 2017, 03:13:38 PM »

If the total width of the door isn't available to persons leaving the area, then the figure used to calculate exit capacity, needs to accurately reflect the total available escape width. Otherwise the flow through the exit will be restricted and slowed, leading to prolonged escape times.
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Mr. P
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« Reply #3 on: December 07, 2017, 11:08:37 AM »

What is width of final exit? Often see nice wide stair and corridors but ending with a 750mm ish door. That's your stopper. Narrowest width dictates. Oh dear it opens inwards... who approved that? Sorry Business owner - max 60 pers.
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paul1969
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Posts: 14


« Reply #4 on: December 10, 2017, 12:04:35 PM »

Thank you all for your responses.  The final exit doors are 1400mm and open outwards in direction of travel.

But....someone has now said that BS9999 calculations shouldn't be used unless we are 100% sure the entire building was built to this guide...which we cannot be 100% sure of!  So, should we be using DCLG guide instead?! Huh  Or another!   Huh
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