How big a hole do you need for a spiral staircase?

Are you looking to save a little space in your property? Then a spiral staircase might be what you a looking for. Whilst they do have space saving properties, they do require a certain sized hole in the floor. Do you have the space for this hole in the upper floor of your property?

Let us have a further look into to what is required.

STAIRWELL

The stairwell is the hole in the upper floor of a property which contains the staircase. This hole is created to achieve safe passage when using a staircase between floors. This opening in the floor needs to be large enough to ensure a user doesn’t bang their head when using the staircase or trap their fingers when using the handrail.

With space at an absolute premium, most people want the smallest stairwell possible to maximise the useable living space. If you are considering changing your existing stair to a spiral or have a loft conversion underway, then what size does the stairwell need to be?

SPIRAL STAIRCASE DIAMETER

The opening in the floor will of course depend on the spiral diameter you are choosing. The floor height will not affect the stairwell opening you require. The choice of diameter will likely depend on location and usage of the spiral. If the spiral is the main stair in the house, then you will need a 1800mm minimum diameter and a secondary spiral 1400mm minimum. However – please ensure you check the spiral diameter requirements with your building inspector.

CLEARANCE

The general rule of thumb is that the hole in the floor should be 100mm larger than the diameter of the spiral staircase. This to give you a knuckle gap clearance between the handrail and the edge of the floor or any surrounding walls. This opening size might be larger than you think. If you were looking to replace an existing straight stair with a spiral then the opening required would likely be a lot wider than the existing.

So, if you were selecting a 1500mm diameter spiral then the hole in the floor should be 1600 x 1600mm square or 1600mm diameter circle. These are minimum sizes, obviously it can be bigger if you have the space. Keep in mind that the opening measurement we are discussing are the finished holes in the floor. So, the opening including any lining / plasterboard finishes.

What size hole do you need for a spiral staircase

diameter of spiral + 100mm = stairwell / opening size

Example – 1500mm diameter spiral + 100mm = 1600mm x 1600mm opening or a 1600mm diameter opening

A common misconception is that a spiral staircase forms a 180 degree turn with the centre column next to the floor. This is not the case. A spiral staircase needs a platform, and the centre column is generally located in the centre of the hole in the floor. That said, there are certain models that are made specifically for a smaller stairwell. The Tulip kit spiral stair for example has a specially made smaller platform which means the hole can be less deep than normal.

IS A SPIRAL STAIR FOR YOU?

Considering the hole in the floor a spiral requires – is a spiral the right choice for you? You might wish to speak to a builder about forming or enlarging the stairwell before committing.

Once you have established a spiral is feasible you need to confirm the diameter requirements with building control (if subject to building control approval). Then for the fun part of choosing a model.

We have an unrivalled selection of spiral staircases from kit models to bespoke systems in all manner of materials and styles. We also have a showroom where you can see, touch and walk up many models.