Hi.

Please help me understand the 4.5m above ground level rule- our Building inspector and Fire Safety inspector said: "The 4.5m is the maximum escape height not the floor level which is why it is shown between two storey levels." and that "The 4.5m rule is indicated in the building regulations as being measured from ground level to the underside of the window."

I thought the 4.5m is the maximum actual floor height above ground. Who's right?

The diagram does look like it implies window height - but all the text points otherwise as Approved Document B uses the following phrase in relation to the point for where Means of Escape requirements become more stringent:
"upper storeys a maximum of 4.5m above ground level"

Appendix D states that a storey is measured from the upper floor surface of the floor in question to ground level and has nothing to do with the escape height (which is actually 5.6m as where escape windows are provided in flats up to 4.5m from ground they can have their lowest point up to 1100mm from the floor level). The specification for windows only details dimensions and not total height.

It's not the most clear!

13 hours ago, AnthonyB said:

The diagram does look like it implies window height - but all the text points otherwise as Approved Document B uses the following phrase in relation to the point for where Means of Escape requirements become more stringent:
"upper storeys a maximum of 4.5m above ground level"

Appendix D states that a storey is measured from the upper floor surface of the floor in question to ground level and has nothing to do with the escape height (which is actually 5.6m as where escape windows are provided in flats up to 4.5m from ground they can have their lowest point up to 1100mm from the floor level). The specification for windows only details dimensions and not total height.

It's not the most clear!

Hm... What about this diagram? Here 4.5m is almost at ceiling level, so can't be showing window height?

That diagram reflects the actual text far better!