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Number of exits - small village hall

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Paul1979
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Number of exits - small village hall

Post by Paul1979 »

Hi, anyone help with a quick query we have for our local village hall...Looking at ADB table 2.2 for guidance as new building and 2.3 for suitable widths.

We have a new small village hall (approx. 11m x 15m = 165m2).

Capacity of 165 (with 1m2 density) and 330 (with 0.5m2 density).

As numbers below 600, is it acceptable to have just two exit doors?? As long as width of said exit door is adequate??

We see the largest door should also be discounted when calculating occupancy...so, if there are only 2 doors, are we then safe using just the 1 smaller door width for capacity calculation? Or should there be 3 doors, then discount the largest to leave us 2?!

We are using the 5mm per person guidance in ADB to work out suitable widths - hope this is correct too!
Last edited by Paul1979 on Sat Aug 15, 2020 10:14 am, edited 1 time in total.
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Re: Number of exits - small village hall

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Re: Number of exits - small village hall

Post by witsd »

I'm going to assume that the people frequenting a village hall will tend to include higher-than-average numbers of elderly, disabled and very young people...

Given that, you may need to significantly err on the side of caution.

Having said that are those capacity figures realistic, or just theoretical maximums? I can't imagine a village hall packed to breaking point as those numbers suggest - what kind of events are they intending on hosting?

I guess what I'm really saying is try to look beyond the raw numbers and consider what situations are actually realistic.
We often think that when we have completed our study of one we know all about two, because 'two' is 'one and one.' We forget that we still have to make a study of 'and.'

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Paul1979
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Re: Number of exits - small village hall

Post by Paul1979 »

Hi witsd, thank you as always for taking the time to reply. Having ready your comments, we fully agree that the figures we calculated are high especially as you say there will be on occasions wheelchair users, elderly people, groups for special needs, etc.

Can we just double check though, is our process of calculating door widths and discounting the doors correct? At present, we only have 2 exits - one is 900mm and the other is 1200mm wide. So if we discount the largest we are left with only 900mm. Our thoughts were to introduce another 1200mm or larger door therefore that would leave us 1200 + 900 = 2100.

Again, many thanks for taking the time to come back to us.
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Re: Number of exits - small village hall

Post by witsd »

If you really just want the maths, then yeah, it's currently going to be something like this:

1) Discount largest door.
2) Confirm width of other door – 900mm.
3) Divide width by 750mm – 1.2
4) Multiply by 40 (the made-up number for how many soldiers can march through a 750mm door in one minute) – 48
5) Multiply by 2.5 (a made-up number of minutes for everyone to safely get out of a theatre while singing the national anthem) – 120 person maximum occupancy with current door arrangement.
6) Adding another 1200mm door would by my maths get you a final total of 280 average persons ( ((900+1200)/750) x 40 x 2.5 = 280 )

*

It should really then be down to you to determine if you think that this is realistic - would the oldies take longer?** Would you have a train of wheelchairs trying to get through and slowing the process down? Children being children? Perhaps you will have to pick out another made-up number to err on the side of caution here!

Once you've done that, then it's finally down to the owners. Are they happy with a significantly reduced capacity, or would they prefer to invest in the new door? Either is fine, as long as they understand the potential consequences for taking the cheaper option and then bending the rules.

* Other calculation systems are also about, of course. The problem is that ultimately all of them are just suggestions based on historical events rather than anything dynamic / situation relevant, but if you aren't completely comfortable making your own conclusions and justifications (and to be clear, there's no shame in that!), then any system cited in a respected document should be safely defensible.

** A quick online search suggests there is evidence that persons over 70 walk 30% more slowly than persons in the 20-30 range, so you could easily justify reducing the 2.5 minutes to just 1.75 minutes, giving totals of 84 (one usable door) and 196 (with the additional door). I'm mainly being silly here, but the info is out there if you really want to try and be scientific about it. Or you could just get them to time their fire drills. :D
We often think that when we have completed our study of one we know all about two, because 'two' is 'one and one.' We forget that we still have to make a study of 'and.'

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