Means of Escape

[Bert]

I recently came across a FRA in which the auditor stated that the rule for discounting an escape stair need not be applied because the building was protected with a sprinkler system installed in accordance with BS 5306 Pt2.  
So far as I am aware, the discounting rule applies at all times unless the stairs are approached via a protected lobby or corridor or if the stair is pressurised.

There is no calculation or other indication that the solution has been fire engineered in any way, so am I missing something here?

[jokar]

Bert, I agree with you ADB lives with pressurised staricases or lobby approach.

[Dinnertime Dave]

I agree too. ADB specifically says that 'the stair discounting rule applies to a building fitted with sprinkler system'

[jokar]

dave,

I have not picked that up before, which section is it in.

[jokar]

Dave,

Sorry, I misread your post and have read 4.20 and 4.21 again and understand what you have posted.

[Bert]

Dave, where does ADB state that the stair discounting rule applies to a building fitted with sprinkler system ?

Jokar, I don't see the relevance of 4.20 and 4.21 of ADB to this situation.

[CivvyFSO]

You using the 2006 version Bert?

Page 47. Para 4.20: The stair discounting rule applies to a building fitted with a sprinkler system. (i.e. You DO discount a stair)
Page 47. Para 4.21: 2 exceptions to discounting: a=smoke control b=protected lobby, topmost storey excluded

[Dinnertime Dave]

Thanks Civvy FSO. I`d spent 20 minutes reading and re reading 4.20 & 4.21 thinking of course it`s relevant. (its called Discounting of stairs) I didn`t think of the obvious.  old ADB 5.11 5.12 & 5.13

[PhilB]

Come on now Dave, if your going to be a code hugger at least hug the current book!!!

[Dinnertime Dave]

Sorry Phil, I am using the current book. I was trying to make sense of Bert`s post. but fair call I`d like to keep my old ADB for comfort and hugging

[Bert]

Gents, just to clarify.

ADB 2006 page 47 clause 4.20 states “The stair discounting rule applies to a building fitted with a sprinkler system”  Therefore, when calculating the escape capacity from a floor, in buildings with more than one escape stair, one stair must be discounted irrespective of whether or not fixed protection is provided.

The risk assessment that I was handed stated that “the rule for discounting an escape stair need not be applied because the building was protected with a sprinkler system installed in accordance with BS 5306 Pt2.” In other words the escape capacity had been calculated using the aggregate width of both escape stairs, which is obviously incorrect. Yes?

[PhilB]

yes

[Mr. P]

Each stair must be discounted in turn...