Height of buildings

[Guest Lyledunn]

I can't quite find a category for this so forgive me for using this one. Can any one advise on the seemingly arbitrary approach to fire safety measures required in buildings of varying heights. I fully understand that taller buildings come with increased risk but the requirements seem to be extreme as one transitions from one height to another. For example, a building of height 17.999m might require 60 min fire resistance but one at 18.01m requires 90. 

[Tom Sutton]

They are arbitrary figures and if you convert them to floors less than 18m is about 6 floors reaching about halfway up the 7 Floor, above 18 m will be 8 floor so dealing with fractions of a metre is not called for.

Also fighting a fire in an a building eight storeys or more, has to be fought from inside the building, because the availability of ariel appliances and their capability are limited and I believe the extra protection is needed.