A wonderful comment has just been made in the Grenfell inquiry about fire risk assessment.

Regarding the lack of water volume or pressure, I do not suppose that even the best engineers could have anticipated such a huge tragedy and demand for water as the Grenfell Tower fire demanded.

A great many countries have formulae based on the building area and height that give a flow and pressure requirement, to get a certain no of litres per unit area per minute onto the top floor,  and this is used to set the no and spacing of street hydrants. (and have done for decades) The hydrants are then flow tested upon commissioning. In the UK it seems the methods we use to space our hydrants do not actually consider the building height, and there is no flow rate testing of the hydrants once in position, only the hydrant design is type tested on some standard test rig. To use that method you do not need to foresee the detail of the fire, only one on the top floor, to scale the problem. There were other matters like dry risers (empty pipes for fire brigade to use) that should have been wet (plumbed in and not needing a fire tender to pump) and a whole slew of other things, so its not so much that one person or organization failed, more the case that almost every person or organisation in the chain cocked up something.

Mike.

Regarding the lack of water volume or pressure, I do not suppose that even the best engineers could have anticipated such a huge tragedy and demand for water as the Grenfell Tower fire demanded.

A great many countries have formulae based on the building area and height that give a flow and pressure requirement, to get a certain no of litres per unit area per minute onto the top floor,  and this is used to set the no and spacing of street hydrants. (and have done for decades) The hydrants are then flow tested upon commissioning. In the UK it seems the methods we use to space our hydrants do not actually consider the building height, and there is no flow rate testing of the hydrants once in position, only the hydrant design is type tested on some standard test rig. To use that method you do not need to foresee the detail of the fire, only one on the top floor, to scale the problem. There were other matters like dry risers (empty pipes for fire brigade to use) that should have been wet (plumbed in and not needing a fire tender to pump) and a whole slew of other things, so its not so much that one person or organization failed, more the case that almost every person or organisation in the chain cocked up something.

Mike.

I presume that the biggest weak link was that it was assumed that a flat was a totally self contained fire compartment, and only one flat would ever need water sprayed into it. That is until the combustible external cladding was added.

Z.

A well written 'stay put' plan has a break point when you decide compartmental isolation has failed - perhaps when more than 3 or 4 flats are affected or if fire reaches some key common parts of the building, when it smartly changes to 'and now we need to start to evacuate' That may be whole bldg, or floor by floor as required.  You have to do that, as you do not want to evacuate for every slice of toast burnt but at the same time you do need to consider the outlier events. Sadly it seems that in this case that break point was not pre-agreed so the decision was dithered.

It  is even more complex in places like hospitals, where evacuate is a whole new level of problem, but then the compartmentalization is tighter and there are things like sprinklers in more complex locations. But those things are designed and done regularly.

I agree it is far too easy to be wise after the fact, but the striking thing here is not that a few things went badly wrong, but that almost nothing was right, even the small stuff.  Mods to the building that cocked up the dry riser arrangements, the cladding, the fire assessment, the street hydrant locations, the information the fire brigade had, the info Thames water had -  the info the occupants had, and that the people getting it wrong were supposed to be subject matter experts.

Mike.