Building components · Stairs & Level Change
Balustrade Infill
Explains the infill as one position within a guarding rather than as the guarding itself, and separates it from the assembly and from the members that bound it.
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 infill is
A balustrade infill is what occupies the zone bounded by the posts, the handrail above and the floor or base rail below. It is the part of a guarding that closes the opening, and it is met as vertical bars, as glass or solid panels, as mesh, as horizontal members, or as some combination of these.
It is treated as a position rather than as a product because the same zone is filled in very different ways for the same reason. What the infill is asked to do — close the gap and resist what is applied to it — stays constant while its realisation changes completely, which is exactly the pattern that makes something a component rather than a material.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not a balustrade and guarding system. That is the whole assembly — posts, rail, infill, base and fixings together — and it is a published building system. The infill is one position inside it, and a change to the infill leaves the rest of the assembly in place.
- It is not a balustrade post. The post is the vertical member that carries the guarding and concentrates load into its base fixing; the infill sits between posts and is carried by them rather than carrying anything itself.
- It is not a handrail. The handrail is the graspable member at the top that a hand runs along; the infill is the zone beneath it, and a guarding can present a handrail with an infill that is never touched.
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.
- guarding infill
- balusters
- spindles
- guarding panel
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- What bounds it — the posts either side, the rail above and whatever forms its base — since the infill is defined by that frame rather than by its own edges.
- How it is held at those boundaries, because load applied to the infill has to reach the posts and then the structure the posts are fixed to.
- What it is expected to close against, which varies with who uses the space and what is on the other side of the guarding.
- Whether it is continuous or made of repeated members, which changes both how it behaves under load and how it is maintained.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Load applied to the infill does not stop there; it travels through the infill into the posts and concentrates at their base fixings, which is where guarding arrangements are commonly governed.
Infill is at hand and foot height along its whole length, so it takes contact, cleaning and weather far more evenly than the members bounding it.
Infill is commonly the last part of a guarding installed, into a frame of posts and rails already set, so its fit depends on the accuracy of what was put up before it.
Replacing or altering infill is commonly possible without disturbing the posts, which is why it is the part of a guarding most often changed during a building's life.
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.
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.
Clarifications
Commonly misunderstood
- That the infill is the balustrade. The balustrade is the whole assembly; the infill is the zone between its members, and it is the part most readily changed.
- That the infill's job is only to fill a gap visually. It is part of how the guarding resists what is applied to it, and load applied to it is carried onward rather than stopping at the infill.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- What holds the infill at the posts, at the rail and at its base?
- Where infill is being changed, does the existing post arrangement suit what is replacing it?
- What is on the other side of this guarding, and what does that mean for what the infill is asked to close?
- Where glass or panel infill is proposed, how is it supported and what happens to the guarding if a panel is removed?
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 guarding. It states no height, gap, opening size, panel thickness, glass classification, load capacity or fire rating, and none can be inferred from it.
- Whether a guarding and its infill satisfy the requirements applying to a building depends on who uses it and on local requirements, and that determination is made by qualified professionals rather than here.
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 →