would like kitset spiral staircase for confine space going to a mezzinane floor 2370 mm high

These stairs go down to my daughters house. They are both narrow and steep with quite a drop on one side. Does anyone have any suggestions on how they could be improved?

I suspect your best course of action would be to contact a local engineer and/or builder -- without knowing what area you are in , and local rules and regulations , any advice wouldn't be much value from us , and quite possibly won't meet compliance .

For structural timber, it's recommended to use H1.2 SG8 grade for interior and H3.2 SG8 grade for exterior. Stairs are typically specified with 290x45mm stringers, but the size may vary depending on the angle of the stairs.