I was looking here and it says " states that a stairway must have not more than 18 and not less than 2 risers in each flight. Where there are less than 2 risers in a flight, it does not comprise a stairway for the purpose of the BCA". So if I have less than 2 risers does that mean there is no minimum height or other regulations? Specifically, I may want to put a raised concrete step in front of a door, at same level as slab under door threshold. Normally a riser has minimum height of 115mm. However, I assume that this does not apply if there is only one riser. Is that correct?