Spiral vs helical staircases

Spiral and helical are the two words people reach for when a staircase curves, and they get used almost interchangeably. They are not the same stair. The difference comes down to one thing: whether there is a column in the middle. Get that clear and you will know which one you are actually asking for, because in most homes it is not the one people say.

Spiral: built around a column

A spiral staircase turns around a single central column, or pole, that runs from bottom to top. Every tread is wedge-shaped, narrow at the column and wider at the outside, and they wind up around that centre like a corkscrew. Because the column carries the load and the footprint is a tight circle, a spiral is the most compact stair there is, which is why it turns up in loft rooms, mezzanines and tight corners. That compactness is also its limit: the treads are narrow where you tread near the column, the pitch is steep, and carrying anything large up one is a fight. The central column is very often steel or cast metal, with timber treads at best, so a true tight spiral is not really a timber joinery stair.

Helical: a freestanding curve

A helical staircase has no central column. It curves upward as a helix, an open spiral, carried on curved strings on the inside and the outside, so the middle is empty and the whole stair sweeps round a void. That is the grand, flowing curve people usually have in their heads when they say the word spiral. Without a column to lean on, a helical stair has to be a properly engineered curved structure, and it needs far more space than a spiral. It is also where timber comes into its own: the curved strings and the continuous wreathed handrail are joinery of the highest order, which makes a helical a very close cousin of the geometric staircase. The main difference is that a helical stands as a freestanding curve, while a geometric stair follows a wall and open well with straight flights running into the curve.

So which are you actually asking for?

Here is the honest bit the spiral-stair sellers tend not to lead with. When someone wants a spiral staircase as a main stair, a feature in a hall, or anything they will use every day with their hands full, most of the time they actually want a helical. They want the sweeping curve, not the tight corkscrew round a pole. A real spiral earns its place where space is the whole problem, a loft or a mezzanine, and even then it is a compromise on comfort. If it is a feature you will love and use, you are describing a helical, and you should plan and budget it as one, because the space and the cost are in a different league.

What BS 5395-2 says

Spiral and helical stairs have their own code of practice, BS 5395-2, which sits alongside the normal building regulations. It sorts these stairs into five categories, A to E, by how public they are and how many people use them. Category A is a small private stair for a few people who know it well, such as one serving a single room. Category B is the main stair to the upper floor of a home. The higher categories, C to E, run up through semi-public stairs to full public and assembly use, and they call for wider, shallower, easier stairs the more people use them. The standard also sets out how the going is measured on the tapered treads: not at the narrow end, but on the walking line, taken 270mm in from the handrail, so the part you actually walk on has enough depth. The everyday rise, going, pitch, handrail and guarding rules still apply on top of that, as on the rise, going and pitch page.

In timber

If you want one of these in timber, be clear which you mean. A tight spiral around a central column is really a metalwork stair that may wear timber treads, because timber cannot do the tight-radius structural column job on its own. A helical is the opposite: curved timber strings, a wreathed timber handrail, the full weight of the joinery craft, and one of the most valuable staircases anyone can own. So if the word spiral is really standing in for that flowing open curve, what you are after is a helical, and that is a timber stair through and through.