The Staircase Doctor writes,

I am often asked about using a spiral staircase as a space saving method of gaining access to a loft conversion. This is in most cases a misconception, a regulation compliant spiral is likely to take up as much floor area any other compliant stair, it is just a different shape.

The situation gets even more complex when you look at what the stair serves. There are different requirements for spiral stairs serving say one bedroom or more than one bedroom.

For instance a spiral staircase serving one room needs what is called a clear width of 600mm.

The clear width is defined as the distance from the outside of the centre pole to the inside of the handrail. In practise this requires a stair of 1400mm or 1500mm in diameter depending on the stair construction. Where as a spiral staircase serving 2 or more rooms needs a clear width of 800mm. Again in practise this equates to a spiral of around a whopping 2000mm in diameter.

Probably the reason that you see so few spirals in large conversion projects.

Let us be honest spirals look great and add a wow factor to any loft project. No one should be put off using a spiral, but you have to realistic about the amount of space they will use. As with all stairs they are more complicated than what you think, and it is advisable to seek professional advice early in the design stage.

Never plough on with the project under the assumption that you get a stair to fit in that corner somehow, it always ends in tears.