Building components · Stairs & Level Change
Stair Tread
Explains the tread as a position within a flight rather than as the visible stair surface, and separates it from the procured trim that terminates that surface at the step edge.
Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.
Overview
What a tread is
A stair tread is the horizontal surface of a single step: the place a foot lands as a flight rises between two levels. It is identified by where it sits in the flight rather than by what it is made of, and the same position is met as a cut timber board, a folded steel pan, a grating panel, or simply the upper face of a cast concrete flight.
It matters because a flight is a repeated element. Every tread in a flight is met in the same rhythm, and how a stair is experienced comes from the consistency of that rhythm rather than from any one step. The tread is also the surface most coverings, trims and edge treatments are applied to, which is why the position and the thing applied to it are so commonly confused.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a stair nosing profile. The nosing profile is a procured trim, published as a material entry, whose job is to terminate a stair covering at the step edge. The tread is the horizontal position that is walked on, and it exists whether or not any nosing is fitted to it.
- It is not a riser. The riser is the vertical face between one tread and the next, and an open-riser flight has treads with no risers at all — which shows the two are separate positions rather than two faces of one element.
- It is not a floor topping. A topping is added over a deck to provide level, mass or a surface across a whole floor plate; a tread is a single step surface set out from the flight it belongs to, not from the floor either end of it.
Terminology
Common names and aliases
These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.
- tread board
- step tread
- stair step
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- What supports it — a stringer at each edge, a carriage beneath, a cast flight or a steel frame — since a tread spans between whatever carries it rather than standing alone.
- The consistency of the flight it belongs to, because a tread that differs from its neighbours is experienced as an irregularity rather than as a step.
- Whether a covering is intended on it, which changes what the walked surface actually is and where the step edge is read.
- The definition and condition of its front edge, which is where wear concentrates and where the step is seen from above.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Treads are set out cumulatively up a flight, so a small inconsistency repeated at each step accumulates rather than cancelling out, and it is noticed at the top rather than at the bottom.
Wear concentrates at the front edge and along the walked line rather than spreading evenly across the surface, so a tread commonly fails locally long before it fails generally.
Recovering a stair changes the walked surface of every tread at once, and the junction between the covering and the step edge is where that work is commonly judged.
A stair is commonly installed after the structure and before the finishes, so treads take site traffic in whatever state they arrive in and are protected, made good or replaced later.
Materials
Commonly formed from
Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.
Materials
Commonly incorporates
Materials this element commonly contains as a distinct constituent part, rather than being made of.
Assemblies
Building systems this element is met in
The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.
Related elements
Neighbouring components
Typed relationships to other elements. There is deliberately no generic “related” category: an edge that cannot be classified does not exist.
Clarifications
Commonly misunderstood
- That the tread is the visible stair covering. The covering is applied to the tread; the tread is the position beneath it, and it remains when the covering is lifted.
- That treads and risers always come in pairs. Open-riser flights have treads and no risers, which is precisely why the two positions are described separately.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What carries the treads in this flight, and how is each tread fixed to it?
- Is a covering intended on the treads, and was that taken into account when the flight was set out?
- How is the front edge of each tread formed, and what terminates the covering there?
- Where a flight is being altered rather than replaced, what is known about the existing treads and their support?
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this element involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this element comes up.
What this entry does not do
- This entry describes a position within a flight. It states no going, rise, width, thickness, slip classification, load capacity or fire rating, and none can be inferred from it.
- Whether a particular stair arrangement satisfies the requirements applying to it is a design determination made against local requirements, not something a reference entry can answer.
Stair & Level Change Elements
The positions that make up a stair and the elements that carry people safely between levels — treads, risers, the members beneath them, and the guarding at the edge.
Browse all stairs & level change entries →