First things first, you appear to be talking about an existing building, although you could be talking about new build - ADB is for new buildings and does not have to be applied retrospectively to existing buildings. There are many, many thousands of homes, maybe millions, that are not up to ADB standard but there is (in general) no legislation that requires them to be brought up to standard. So we have fire deaths - mind you, we still get fire deaths in code compliant homes.
If this is an existing home then you don't have to do anything (unless you or someone else has made material alterations without applying for Building Regs approval). But you might like to bring the house up to the modern standard for peace of mind.
If you are seeking this peace of mind or if this is new build (or an extension) you've found the right paragraphs. There's no need for sprinklers as you have no floor over 7.5m. On the assumption that there are no alternative exit routes from upper floors, you should provide a protected staircase serving the upper floors. No more than this is required.
If you do have an alternative escape route from an upper level (maybe you're on a hill, for example) then you can look at diagram 3 for your guidance - but, be aware, if the alternative way out is from the lower of the two floors above 4.5m then, as well as separating off the ground floor from the upper part of the stair enclosure, you would also have to protect (with FR) that part of the staircase above the separation (so that people on the top floor can safely descend to the level with the alternative exit).
With two floors above 4.5m your top floor must be pretty cose to 7.5m.
Stu
