In message , Theo Markettos
writes
I'm not sure I quite follow you... this circle is to prevent people falling
down the stairs which aren't enclosed?

How would the trapdoor work around the handrail?

Do you mean the door is likely to obstruct the handrail when open? I


How about a sliding door? As it is a new build could you design in
something to slide across the gap from under the upstairs floor?
--
Bill