Staircase Capacity Calculations

[Penfold]

Hi all

I'm looking at building evacuation form 1st floor meeting rooms/conference centre. All the tables I can find (Document B, government guides, course notes)to work out Discharge capacity for staircase start at the width of stair being 1000mm. How do you calculate the capacity when a taircase is les than 1000mm width?

Thanks

Penfold

[Ian Rienewerf]

There appears to be a little bit of wiggle room on minimum stairway widths, so long as the stairs are not the pinch point. See the statement in Paragraph 2.21 - Stairs should be at least as wide as any storey exit leading onto them.
So I would assume you could use the standard exit width calculations on table 2.3.
This would drop your capacity from 150 people at 1000mm stairway width, down to 60-people for an exit width of 750mm.

Note: The 850mm exit width restrictions do not apply if there is only 1x escape route.
You would be limited to 60 occupants already, due to the restriction listed on table 2.2 = "60 people maximum if there is only 1x escape route from a room, tier, or storey."

[Penfold]

Thanks Ian much appreciated