At a glance
| Part | What it is | Also called, or defined in |
|---|---|---|
| Tread and riser | The tread is the surface you step on. The riser is the vertical closing piece, or the gap if the step is open. | Open risers are limited by ADK paragraphs 1.6 and 1.9. |
| Nosing | The leading edge of a tread, often projecting past the riser. | ADK Appendix A; paragraph 1.7 on contrast and projection. |
| Going and rise | Going: the horizontal distance from one nosing to the next. Rise: the height between consecutive treads. | BS 585-1, 2.5; ADK Appendix A. US: run, tread depth. |
| String | The sloping board that carries the treads: closed (housed) or cut (open). | Stringer in the US. Wall string, outer string. |
| Newel | The post at the start, turn or end of a flight that anchors the rail. | Newel post; a half newel sits against a wall. |
| Handrail, baluster, base rail | The rail you hold; the vertical infill below it; the rail on a closed string that carries the infill. | ADK Appendix A and 1.34 to 1.37. Spindle in UK trade use. |
| Bullnose, curtail, volute | Starting steps with a curved end, and the scroll at the end of a continuous handrail. | Sources use bullnose and curtail differently: see below. |
Plain-words definitions. Approved Document K (2013, England) Appendix A and BS 585-1:1989 clause 2 were read; BS EN 14076 and BS 5395-1 in BSI's free preview only. No regulatory figure is quoted.
The parts on one drawing
The drawing below is a straight flight of seven risers seen from the open side, with a cut string, a newel post at each end, balusters and a handrail. It is a schematic: the proportions are drawn for clarity and are not a design. The first view uses the words people use most; the second numbers 23 parts, and the table after it says what each one is.
Two definitions are worth fixing before anything else, because the rules are written in them. The rise is the height from one tread to the next, and the going is the horizontal distance from one nosing to the next. Approved Document K (2013 edition, England) defines both in its Appendix A and calls the nosing the leading edge of a tread; the rise-and-going figures themselves are on the library sheet Stair rise, going and headroom.
Key to the numbered drawing
23 numbered parts. Numbers 13 and 14 (going and rise) are shown on the small inset because they are easier to see on a single step. Which parts a given stair has depends on its design: a closed string has no cut profile, a stair with no landing has no trimmer, and a cantilevered stair has no string.
| No. | Part | What it is |
|---|---|---|
| 1 | Newel post | The large upright post at the start, turn or end of a flight. It anchors the handrail and takes the ends of the strings. |
| 2 | Newel cap | The finishing piece on top of a newel post. A shaped or ornamental one is often called a finial. |
| 3 | Handrail | The rail you hold. Approved Document K, Appendix A: a rail, at hand height or a little higher, for people to hold for support. |
| 4 | Baluster | The vertical infill between the handrail and the tread or base rail. UK trade usage often says spindle for the same part. |
| 5 | Top newel | The newel at the top of the flight, fixed to the floor structure at the stairwell edge. |
| 6 | Newel drop | The part of a newel that continues below the floor edge, often turned (a pendant). It hides the fixing to the trimmer. |
| 7 | Cut string | The sloping board on the open side, cut to the profile of the steps so the treads show. Often called an open string. |
| 8 | Tread | The horizontal surface you step on. |
| 9 | Riser | The vertical piece closing the front of a step. A stair with none has open risers. |
| 10 | Nosing | The leading edge of a tread (Approved Document K, Appendix A). It often projects past the riser below. |
| 11 | Scotia | A concave moulding under the nosing that covers the joint between the tread and the riser. |
| 12 | Pitch line | The notional line joining the nosings. Pitch is its angle to the horizontal; handrail height is measured from it. |
| 13 | Going | The horizontal distance from one nosing to the next (BS 585-1, 2.5). Approved Document K measures the depth of a tread from front to back, less any overlap. |
| 14 | Rise | The height between consecutive treads (Approved Document K, Appendix A). |
| 15 | Total rise | The height between the two finished floors a flight connects. Divide it by the number of risers to get the rise. |
| 16 | Handrail height | Measured vertically from the pitch line on the flight, and from the floor on a landing. |
| 17 | Upper floor or landing | The level floor at the top of a flight, or between two flights. |
| 18 | Trimmer joist | The joist across the stairwell opening that carries the floor edge and the top of the string. |
| 19 | Apron lining | The board that covers the exposed edge and joist ends at the stairwell opening. |
| 20 | Soffit lining | The lining, often plasterboard, under the flight. Where a stair is part of the fire protection it forms part of the protection. |
| 21 | Spandrel | The triangular space under a flight, often used as a cupboard. |
| 22 | Finished floor | The completed floor surface at the foot of the stair. Total rise is measured from it. |
| 23 | Flight | A continuous series of steps between two landings or floors (Approved Document K, Appendix A). |
Inside a step, and three ways to carry a flight
Most disagreements about stair parts are really disagreements about construction, so it helps to see how a step is put together. The section below is one step of a traditional timber stair. The tread projects past the riser as the nosing, and a scotia moulding under the nosing hides the joint. The top of the riser sits in a groove in the underside of the tread, and angle blocks (glue blocks) stiffen the corner behind it. In a closed string the tread and riser ends sit in tapered housings and are held there by glued wedges.
BS 585-1:1989, the specification for domestic timber stairs with closed risers, covers exactly these items: housed and wedged strings, glue blocking, tenoned string ends, built-up newels, the bullnose step and winders. It sets minimum finished sizes for treads, risers, strings and newels, which this sheet does not reproduce: ask the partner joiner which standard and sizes they build to, and have them show the sizes on the shop drawing.
Closed, cut and cantilevered
The second drawing shows the three ways a flight is usually carried. A closed string (or housed string) is a board that hides the step profile; the treads and risers are housed into it, and a base rail on top of it carries the balusters. A cut string has the profile of the steps cut into its top edge, so the treads show from the side and the balusters stand on them. A cantilevered stair has no string: each tread is fixed into a wall (or a spine) and carried out from it, which makes the wall and the fixing an engineering matter. The words open string and cut string are used for the same thing in most of the trade sources read, but not all, so draw the string rather than relying on the word.
Shapes, turns and starting steps
Two plan words carry real meaning in the regulations. Approved Document K defines a helical stair as a stair in a helix around a central void, and a spiral stair as a stair in a helix around a central column; both are designed to BS 5395-2 (paragraph 1.28). A flight is a continuous series of steps between landings. A winder is a wedge-shaped tread used to turn a stair without a landing; BS 585-1 defines a winder flight as a small group of winders encompassing not more than a half turn. Approved Document K has its own rules for tapered treads (paragraphs 1.25 to 1.27), so a stair with winders should be checked against them.
Starting steps, curtails and volutes
The foot of a stair is where the terms are used most loosely. A square start ends the first tread square against the newel. A bullnose rounds the end of the first tread in a quarter circle, usually around the newel. A curtail carries the end of the first tread out past the string and curls it, and a continuous handrail then ends above it in a volute, a scroll. Those are the senses in which most UK stair makers use the words, but the next section shows how other sources differ.
Where the words differ
Stair words are not fixed, even among the documents that define them. Approved Document K, BS 585-1, a trade body and a handful of stair makers were read for this sheet, and they agree on the core words (tread, riser, nosing, rise, going, flight, handrail, newel) and part company on the ones in the table. The rule that follows is simple: where a word matters, draw the part and name it on the drawing.
The European terminology standard for timber stairs, BS EN 14076:2013, defines stair types, measurements, types of step, stair components, balustrade components and spiral stairs, and BS 5395-1:2010 includes a stair terminology figure and a definitions annex. Both are paywalled. We could read only their free previews, so this sheet does not claim that any definition here matches them word for word.
| Word | Closest to a standard or regulation | Other usage found | What to do on a drawing |
|---|---|---|---|
| Going | ADK: the depth of a tread front to back, less any overlap with the tread above. BS 585-1: nosing to nosing. | One UK stair maker measures riser face to riser face. US sources use run or tread depth, and Wikipedia says tread depth differs from going by the nosing. | For a uniform flight these give nearly the same figure. State on the drawing which is meant, and the number of goings (one fewer than the risers). |
| String | Most UK sources: string. BS 585-1 uses it throughout. | US sources: stringer. One 1900s US text also uses stringer for the cut-and-mitred side board. | Say string or stringer once and stay with it. |
| Open, closed and cut string | A closed string hides the step profile; a cut string shows it (most sources). | Some sources call a cut string an open string, one lists an inner closed and an outer open string on the same stair, and one page uses the words in a garbled way. | Draw it. Say 'cut (open)' or 'closed (housed)'. |
| Baluster and spindle | Many UK stair makers: spindle, or baluster as an alias. | US trade bodies and Wikipedia: baluster; spindle is a furniture term. The word banister is used for the handrail, the balusters or both. | Use baluster for the part and balustrade for the whole barrier; say banister for neither. |
| Bullnose | UK stair makers: a starting step with a rounded end, one or both sides. | A US trade body page: a step whose leading edge projects past the riser. A 1900s US text calls the semicircular lower step a hull-nose. | Say 'bullnose starting step' and draw it in plan. |
| Curtail | UK stair makers: a decorative starting step that sweeps out and curls, housing the volute. | A US trade body page: also a horizontal member at the bottom of a stringer. A 1900s US text: a step whose outer end is a horizontal spiral. | Say 'curtail starting step' and draw it in plan, left or right hand. |
| Carriage | Old texts: a timber under the treads (horse, springing tree) that carries the stair. | A modern stair maker's glossary equates it with a stringer. | Avoid the word; name the member and its job. |
| Pitch | ADK: the angle between the horizontal and the line joining the nosings. BS 585-1 defines the pitch line. | Wikipedia: pitch and slope are used for the rise to going ratio as well. | Give pitch in degrees and name the pitch line. |
| Landing and platform | A level floor at the top, bottom or between flights. | One glossary calls the top tread of a spiral stair a platform. | Say landing only for a floor. |
What to name on a drawing
A stair drawing that names its parts leaves less to interpretation at tender. These are the items worth naming, with the part each one controls:
- Setting out: total rise finished floor to finished floor, number of risers, rise and going, pitch line. Measured on site, not taken from the plans (see Site survey and dimension verification).
- String: closed (housed) or cut (open), species, thickness, and the side it is on (wall string, outer string).
- Treads and risers: finished thickness, closed or open risers, nosing profile, scotia or none.
- Newels: square or turned, section, cap profile, drop (pendant) or none.
- Starting step: square, bullnose (one or two ends) or curtail, left hand or right hand, drawn in plan.
- Handrail and balusters: handrail profile and section, baluster profile and spacing, base rail or none. The heights, gaps and loads belong to the balustrade sheet and the current Approved Document, not to this one.
- Soffit and fire: whether the underside is lined and whether the stair forms part of a fire-protected stairway (take advice from the fire engineer; see the fire documentation matrix).
Naming a part correctly does not make a stair compliant. Rise, going, headroom, handrail height, guarding and loads are set by the regulations for the project's nation: see Stair rise, going and headroom and Balustrade and handrail rules.
Specification wording
Paste into your schedule or specification and replace anything in [square brackets] with your own figures. Wording is a starting point: your specification governs.
Stair [S1], [straight / quarter turn with winders / half turn with half landing], [ ] risers at [ ] mm rise and [ ] mm going (nosing to nosing), total rise [ ] mm finished floor to finished floor, verified on site. String [closed (housed) / cut (open)], [species], [ ] mm thick. Treads [ ] mm, risers [ ] mm, [closed / open]. Nosing [profile ref]; scotia [ref / none]. Parts named as on key drawing [ref].
First step [square / bullnose, one end / bullnose, both ends / curtail, left hand / right hand], drawn in plan at 1:[ ]. Newels [square / turned], [ ] mm, cap [profile ref], drop [profile ref / none]. Handrail ends in [volute / newel cap / easing].
Handrail [profile ref], [ ] mm, [species], [newel to newel / continuous]. Balusters [profile ref], [ ] mm at [ ] mm centres, housed into [handrail and base rail / handrail and tread]. Heights, gaps and loads to the current Approved Document K and the engineer's design, which govern.
Terms used on this page
- Going
- Horizontal distance between two consecutive nosings (BS 585-1, 2.5). Approved Document K measures tread depth, less overlap.
- Rise
- The height between consecutive treads (Approved Document K, Appendix A).
- String
- The sloping board that carries the treads. Closed (housed) hides the steps; cut (open) shows them.
- Bullnose
- A starting step with an end rounded in a quarter circle. Sources use the word differently.
- Curtail and volute
- A starting step whose end sweeps out and curls, below the scroll (volute) at the end of the handrail.
Standards and sources
- BS EN 14076:2013 Timber stairs. Terminology: BSI: Current, 31 Jan 2014 (2004 edition withdrawn). Free preview only.
- BS 585-1:1989 Wood stairs, closed risers, domestic: BSI: Current, 30 Jun 1989. Preview only.
- BS 5395-1:2010 Stairs, straight flights and winders: BSI: Current, 28 Feb 2010. Free preview only.
- Approved Document K, 2013 edition (England): Appendix A read 6 Nov 2026.
- BWF Stair Scheme Design Guide 1 (2017): trade body guide.
Questions we are asked
What is the difference between a closed string and an open string?
A closed (housed) string is a board that hides the profile of the steps: the treads and risers are housed into it. An open string is one with the step profile showing, which most sources call a cut string. A few sources use the words differently, so ask for the string to be drawn and named as 'cut (open)' or 'closed (housed)'.
What is a newel, and how is it different from a baluster?
A newel is the large post at the start, turn or end of a flight; it anchors the handrail and takes the ends of the strings. A baluster is one of the slim vertical members between the handrail and the tread or base rail. Many UK stair makers say spindle for a baluster.
What are a bullnose step, a curtail step and a volute?
In the senses most UK stair makers use, a bullnose is a starting step with a rounded end, a curtail is a starting step whose end sweeps out and curls, and a volute is the scroll at the end of the handrail that sits above a curtail. Other sources use bullnose and curtail differently, so draw the starting step in plan.
Is the going the same as the tread depth?
Not always. Approved Document K defines going as the depth of a tread front to back, less any overlap with the tread above, and BS 585-1 measures it from nosing to nosing. A tread board can be wider than the going because of the nosing, and some sources measure from riser face to riser face. On a uniform flight the figures are close, but state which is meant.
What are the winders on a staircase?
Winders are wedge-shaped treads that turn a stair without a landing. BS 585-1 defines a winder flight as a small group of winders encompassing not more than a half turn. Approved Document K has separate rules for tapered treads, so check them for any stair with winders.
Which standard defines the terms for timber stairs?
BS EN 14076:2013, Timber stairs: terminology, is the European terminology standard, and BS 5395-1:2010 includes a terminology figure for straight stairs. Both are paywalled and this sheet read only BSI's free previews, so use it as a plain-English guide and check the standard if a contract names it.
Is a spiral stair the same as a helical stair?
No. Approved Document K defines a spiral stair as a helix around a central column and a helical stair as a helix around a central void. Both are designed to BS 5395-2 under paragraph 1.28 of the document.
Download the factsheet
A two-page A4 PDF with the numbered parts drawing and key, the terms and specification wording, to keep with your project file.