Do spiral staircases save space?
The simple answer is: NO.
Spiral stairs do not save space. If they did we would see more spiral stairs in small properties
Let’s see why.
In this example, I will look at the difference in space required for a straight flight of stairs as opposed to a spiral flight.
To keep things simple, I am going to do the calculations in metric; so we work in whole numbers and decimal points, rather than imperial with fractions.
Dimensions.
We will use the same going through the centre line of the spiral flight as we use for the straight goings. (Diag 1)
G = 250mm – 9 7/8″
R = 185mm – 7 1/4″
Tread width = 900mm – 35 3/8″
P = 36.5º
footprint/headroom.
The total rise will be calculated at 2M – 6′ 6″ as this is generally the minimum head clearance allowed.
Therefore the minimum space to allow someone to walk under the flight and headroom required over the flight.
Therefore the space that needs to allowed for in the calculations. (Diag 2)
Landing area.
For the purposes of this example, I have not included the landing area or clear space that should be left at the top and bottom of the flights.
The area used.
Spiral flight.
For the spiral flight area in this example, we will use only the space the flight uses. (Diag 4)
I have used the area results given by the cad programme, this can be calculated longhand.
When the flight is set in the corner of a room it will restrict the access to the space between it and the walls, increasing the amount of area that is used by the flight.
Straight flight.
The straight flight will normally be set against a wall but the corners of the room are included within the staircase area. (Diag 5)
Spiral flight area minus straight flight area.
As we can see from the area occupied, that the spiral although only small, takes up more space. (Diag 6)
So we can deduct the straight flight area from the spiral to find the diffence in space.
2.509 – 2.475 = 0.034M²
about 52″²
When we take into acount the 3 restricted corner areas this changes to:
3.090 – 2.475 = .615M²
about 6’6″²
This equates to approximately 20% increase in area that the sprial staircase uses over a straight flight.
Landing area.
On straight flights that sit over each other, the landing area has to run from the top of one flight back to the start of the next flight, on a spiral stairs a landing may be built into the flight; so staying within the staircase area already occupied.
So does this save space?
Even when the spiral stairs are used and the landing is within the spiral restraints, a landing area outside of the spiral will normally still be required to get to the rooms and allow for the doorways.
when in an office or open plan scenario, where the flights are in the middle of the open-plan area, landings may not be required; so only the spiral area will be required and therefore will be as above with just the flight areas used.
Flights with landings
Here we will allow a 1 Meter landing area, to the side on the spiral flight and at each end on the straight flight. (Diag 7)
Here we can see the spiral with landings takes up less space than the straight flight but this only shows one landing, when we add in another 1.8M² for the other landing this increase the space for the spiral flight.
Spiral with landing area top and bottom we get 5.506 + 1.8 = 7.3M²
the straight flight with landings at each end and the return landing running between them, alongside the flight takes up 8.5M²
so a saving of 1.2M²
Add winders in.
We can change the layout of the straight flight by adding winders top and bottom, the 3 winders will use the same space as 3 straight goings but then the landing area required is in the same area as the return landing thereby utilising the same space. (Diag 8)
This now reduces the landing area required by around 3.3M² reducing the total area required and making it more compact than the spiral.
This now changes to:
Spiral area 7.3 M²
straight flight with winders area 5.22 M²
Other considerations.
- In the example used here, the stairs are drawn with a central column, when increasing the size of the spiral, a stringer may be required.
- The cost of curved stairs will be greater than that of straight flights.
- Creating storage cupboards under a straight flight is much easier than under a spiral flight.
- The spiral staircase design is more restricted by landing positions.
- Spirals are more restrictive for carrying large items up and down.
- Spiral stairs are ideal for external fire escapes where space is not a restriction.
- Straight flights will require plastering into the wall and the stringer skirting transition factored in.