Paul Houghland

Hello everyone, I was wondering if anyone can advise me. I'm risk assessing a number of properties that have existing external fire escape stairs, possibly over 50 to 60yrs old. I'm aware they will require a structural survey if they have had one recently. I was wondering about the gaps between the railings, some of them have gaps of 250mm, big enough for a child or small adult to easily fall through. Do these fire escapes need to conform to the current standard, I think gaps should be no more than 100mm. Or do they have grandfather rights?