Access structures
A stairway or a platform is a frame with people on it, which changes the design basis completely. Load cases become defined, guard rails become part of the structure, and stair geometry is regulated rather than chosen. This page covers how a bolted access structure is put together, what has to be decided before it is drawn, and where aluminium is and is not the right material.
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Stairway and platform systems are bolted access structures built from aluminium profile: walk-on platforms with guard rails and toe boards, and stairways connecting levels. They are assembled from standard sections and connectors, shipped flat, and built on site without welding. The design is driven by a defined load case and by the applicable access standard, not by the frame sections alone.
Below: the decisions that have to be made before the structure is drawn, how stairs differ from platforms, and where aluminium is the wrong material.
A platform that will be walked on has to be designed for a defined load, and that load is set by a standard rather than by judgement. Four parameters drive everything downstream.
| Parameter | What it decides |
|---|---|
| Design live load | The load the deck and its supports have to carry, including people and whatever they may be carrying or placing |
| Point load | A concentrated load at any point, which usually governs the deck rather than the frame |
| Guard rail load | The horizontal load a person can apply to a rail; this is a structural load on the frame, not a fitting |
| Applicable standard | Determines the load figures, the rail heights, the toe board height and the stair geometry |
Where the structure falls under a specific regulation — a workplace access standard, a machinery standard or a client specification — that document governs. Confirm which one applies before the layout is drawn, because a change to the standard after design usually means a rebuild.
The frame does not decide the deck span. The decking material does, and the frame layout has to follow it.
| Decking | Support spacing driver | Notes |
|---|---|---|
| Aluminium or steel grating | Span rating of the grating for the design load and the allowable deflection | Open decking drains and does not collect debris |
| Solid plate | Plate stiffness between supports; usually the shortest spacing | Slippery when wet unless treated; consider a slip-resistant surface |
| Plywood or board | Board span rating; longest spacing but least durable | Normally temporary structures only |
| Timber decking | Joist spacing for the design load | Requires a separate joist layer above the frame |
The practical consequence is that the frame layout is usually fixed by the decking the customer wants, and the frame sections are then chosen to suit that layout rather than the other way round.
A stair is not a ladder and it is not a ramp. Its geometry — the rise, the going and the pitch — is specified by the applicable standard, and there is very little freedom to design around it.
The most common design error on a bolted access structure is treating the guard rail as an accessory. It is not: the rail load is applied at the top of the rail, which puts a moment into the platform frame and into the posts.
Three consequences follow.
Practical point: toe boards are also a requirement, not a detail. They stop tools and material being kicked off the platform, and their height and the maximum gap below them are specified by the same standard that sets the rail height.
| Criterion | Bolted aluminium | Welded steel |
|---|---|---|
| Corrosion | No painting required; anodised or mill finish | Requires painting or galvanising, and fails at weld seams |
| Weight | Low; a platform can often be handled without a crane | Heavy; lifting equipment usually needed |
| Site work | Bolted with hand tools; no hot work permit, no welding skill | Welding, grinding and repainting on site |
| Re-configurability | Can be extended, shortened or re-used | Permanent |
| Stiffness and damping | Lower modulus and low damping; needs bracing and can feel lively underfoot | Stiffer and better damped |
| Best for | Access structures that are built on site, moved, or used in corrosive or clean environments | Permanent, highly loaded or long-span structures |
The stiffness difference is worth planning for. An aluminium platform can meet a stiffness requirement and still feel springy underfoot, because the perceived liveliness is about damping as much as deflection. Diagonal bracing in the plane of the deck framing, and supporting the deck at closer centres than the minimum, both reduce it.
A bolted access structure is normally supplied as marked sub-assemblies cut to a cut list, with the connectors, fasteners and decking. Four practices keep site work predictable.
Send the layout, the finished floor levels, the design load case and the applicable standard, together with the decking you intend to use. From that we can specify the frame sections, the connectors, the guard rail arrangement and the decking support spacing. If the standard has not been confirmed yet, say so — it is the single item most likely to change the design. Standard sections are quoted within one working day. Related ranges: 50 series aluminium profiles, 60 series aluminium profiles, floor elements, levelling feet, joining plates and panel installation elements.
FAQ
The design live load, the point load and the guard rail load are all set by the applicable access standard rather than by judgement. Confirm which standard applies before the layout is drawn.
It is set by the decking material, not by the frame. Grating, solid plate and board all have different span ratings for the design load and allowable deflection.
Rail heights, the number of rails and the toe board height are specified by the applicable standard. The rail is a structural load on the frame, not an accessory.
Yes. The rail load bends the post at its base, so the post base joint is a moment connection and usually needs a plate or a second connector.
Aluminium has a lower modulus and low damping. Diagonal bracing in the deck plane and closer support centres both reduce the perceived liveliness.
Yes, entirely bolted with hand tools. That is the main advantage - no hot work permit, no welding skill and no repainting on site.
Usually as marked sub-assemblies cut to a cut list with the connectors, fasteners and decking, assembled on site.
It can be, particularly where corrosion or cleanliness matters. For a permanent, highly loaded or long-span structure, a welded steel frame is often the better engineering choice.
Send the drawing, the section size or a sample and we will confirm the alloy, the tolerance, the finish and the commercial terms. Quotes for standard items normally go out within one working day.
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