Types of scaffolding: every arrangement, drawn and explained

Ask what type of scaffold a job needs and you are really asking three separate questions: how the structure stands up, what it is for, and what it is built from. Most confusion about scaffold types comes from mixing those three together — a birdcage and a system scaffold are not alternatives to each other, because one describes the arrangement and the other describes the components.

This is every type a UK scaffolding contractor is likely to price, grouped by the question it answers. Each one is drawn, because the difference between a cantilever and a truss-out is geometry rather than vocabulary.

How scaffolds are classified

Three axes, and a scaffold has a position on all three at once.

• –How it is supported. Independent, putlog, cantilever, truss-out or suspended. This is the load path — where the weight goes and what carries it.
• –What it is for. Facade access, a birdcage over a ceiling, a loading bay, a temporary roof, a gantry over a footpath. This is the purpose the arrangement serves.
• –What it is built from. Tube and fitting or system scaffold. This is the kit, and it is independent of the other two.

So a single structure might be an independent tied facade scaffold in system components — one answer from each axis, and none of them contradicting the others.

Every type at a glance

The pattern in that last column is worth noticing: everything that stops standing on the ground stops being coverable by a compliance sheet. That is the single most useful thing to know when a job is being priced, because it is the difference between a quote you can send this afternoon and one that waits on a designer.

Access scaffolds: getting to a face

The largest group by far, and the one most jobs are. These exist to put people and material next to a wall.

Facade scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/facade-scaffold/diagram.svg" alt="facade scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/facade-scaffold">What is a facade scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

The default. Two rows of standards running along an elevation, joined by ledgers along the length and transoms across the width, boarded out at whichever lifts the work needs.

It is what most people picture when they hear the word scaffold, and it is the arrangement TG20 covers most comprehensively. An ordinary facade scaffold within the usual bay lengths, lift heights and tie patterns will very often be coverable by a compliance sheet rather than needing a design.

Independent tied scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/independent-tied-scaffold/diagram.svg" alt="independent tied scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/independent-tied-scaffold">What is a independent tied scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

Strictly this describes how a facade scaffold stands rather than being a different type. Independent means the building carries none of the vertical load — the scaffold's own standards take everything to the ground. Tied means the building resists the horizontal, through the ties.

Both halves of the name matter. A scaffold that is independent but inadequately tied is not the structure that was designed, and it will stand up perfectly well during erection while being nothing like adequate once it is sheeted.

Putlog scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/putlog-scaffold/diagram.svg" alt="putlog scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/putlog-scaffold">What is a putlog scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A single row of standards, with the inner end of each horizontal member — the putlog — built into the brickwork as it rises. The wall is part of the structure.

Historically a bricklayer's scaffold, and much less common now, because it needs brickwork capable of carrying load and that rules out most modern construction and most refurbishment. The term survives mainly in the putlog coupler, which is still used on independent scaffolds.

Birdcage

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/birdcage/diagram.svg" alt="birdcage — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/birdcage">What is a birdcage?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A grid of standards across an area rather than along a face, boarded across the top to give one platform over the whole footprint. Where a facade scaffold is a wall of scaffold, a birdcage is a floor of it.

The standard answer to work on a large ceiling — a church roof, an atrium soffit, a plant room. Built internally more often than not, which brings its own questions: whether the existing floor can take the concentrated load at every standard, and what there is to tie to when you are inside a building rather than against one.

Towers: access to a point

Where a facade scaffold serves a run, a tower serves a spot. Height relative to base is the governing consideration rather than load, which is a different design problem.

Static tower

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/static-tower/diagram.svg" alt="static tower — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/static-tower">What is a static tower?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A free-standing tower fixed in position. Stability comes from the base dimensions, the bracing and, where the height demands it, ties or outriggers. Towers are frequently erected by people who are not scaffolders, which is where most of the trouble with them begins.

Mobile tower

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/mobile-tower/diagram.svg" alt="mobile tower — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/mobile-tower">What is a mobile tower?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A tower on castors, normally a prefabricated aluminium system. The castors are both the point and the problem: a tower that can be moved will be moved, including while somebody is standing on it.

Worth knowing that mobile access towers sit outside BS EN 12811, which explicitly excludes horizontally movable platforms. They are covered by their own standard and by the manufacturer's instructions, and those instructions are part of the safe system of work rather than a suggestion.

Staircase tower

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/staircase-tower/diagram.svg" alt="staircase tower — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/staircase-tower">What is a staircase tower?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A tower containing stair flights rather than ladders. On any scaffold in use for more than a few days this is the access arrangement that actually gets used properly — people can carry things, move faster, and are far less likely to fall.

It takes a footprint, and that footprint has to be planned rather than found later. A stair tower is also on the critical path: if it has to move to let a delivery through, the access moves with it.

Where there is no ground

The hardest group, and the one that always needs a designer. Each of these exists because the ground beneath the work is unavailable — a railway, a river, a live road, a lower roof, a pavement that cannot be closed.

Cantilever scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/cantilever/diagram.svg" alt="cantilever scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/cantilever">What is a cantilever scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

Supported at one end only, projecting from the building, with the supporting members running back into the structure and anchored there. Everything depends on that anchorage.

There is no compliance sheet for a cantilever. It is a bespoke design every time, and the loads in the supporting members are not something to estimate on site.

Truss-out scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/truss-out/diagram.svg" alt="truss-out scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/truss-out">What is a truss-out scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A framework projecting from the building that the working scaffold then sits on, used where the scaffold has to start at height and a cantilever alone would not carry it. Load goes into the building rather than the ground, which makes the connection to the building the critical element — frequently through girder couplers onto structural steel.

Suspended scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/suspended-scaffold/diagram.svg" alt="suspended scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/suspended-scaffold">What is a suspended scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

Hung from above on ropes or rigid supports rather than standing on anything. The load goes upward into the structure, and the suspension rigging is effectively the whole scaffold as far as safety is concerned.

Rope-suspended platforms are also outside BS EN 12811. This is specialist suspended access rather than a variant of ordinary scaffolding, and treating it as the latter is how it goes wrong.

Bridge scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/bridge-scaffold/diagram.svg" alt="bridge scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/bridge-scaffold">What is a bridge scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

Where standards cannot land — a doorway, an access route, a road — the scaffold is bridged across on beams. The important thing to understand is that bridging does not remove load, it moves it: the standards flanking the gap carry what the missing ones would have, and are set out accordingly.

A beamed bridge of any size is one of the commonest reasons an otherwise ordinary scaffold falls outside its compliance sheet.

Purpose-built structures

Arrangements built to do a specific job rather than to provide general access.

Loading bay

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/loading-bay/diagram.svg" alt="loading bay — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/loading-bay">What is a loading bay?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A strengthened section built to take material landed by crane or hoist, to a higher duty than the scaffold around it — closer standards, heavier members, and a stated safe working load.

Edge protection at a loading bay is a particular problem, because the edge has to open to receive material and close again afterwards. Gates are the arrangement that survives being used; guard rails removed and leant against the wall are the arrangement that does not.

Temporary roof

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/temporary-roof/diagram.svg" alt="temporary roof — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/temporary-roof">What is a temporary roof?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A scaffold-supported roof over a building, usually sheeted, keeping weather off the work below. It turns a scaffold into a building envelope, and that changes the loading completely: wind on a large sheeted roof is a substantial force, and snow is a vertical load the scaffold below would otherwise never see.

Temporary roofs are explicitly outside BS EN 12811 and are always designed. The scaffold underneath is carrying loads from the roof, so the two are one structure for design purposes even though they are built in stages.

Chimney scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/chimney-scaffold/diagram.svg" alt="chimney scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/chimney-scaffold">What is a chimney scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

Access around a stack at roof level, supported off the roof structure, off a scaffold at eaves level, or on a framework spanning the roof. The recurring problem is that roof structures are not designed to carry scaffolds, so what the roof can take has to be established rather than assumed.

Pavement gantry

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/pavement-gantry/diagram.svg" alt="pavement gantry — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/pavement-gantry">What is a pavement gantry?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

A structure spanning a footpath, carrying a protected walkway beneath and usually a working platform above. It keeps a footway open under a working scaffold, which is frequently a condition of the licence to occupy the highway at all.

Because the public walks underneath, the deck above them has to be sealed against anything falling. Gantries almost always involve a highway authority licence, so the programme depends on permission as much as on construction.

What it is built from

The last axis, and the one that cuts across all of the above. Every type described so far can be built in either kit, and most firms run both.

Tube and fitting

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/tube-and-fitting/diagram.svg" alt="tube and fitting — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/tube-and-fitting">What is a tube and fitting?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

Loose steel tubes joined by couplers at any position along their length. Tube to BS EN 39 and fittings to BS EN 74, which is what lets components from different suppliers interoperate.

It will follow any geometry a building presents, which is its whole advantage. It costs time and consistency to do it: every connection is made by hand and torqued, and the fitting count on a large scaffold is substantial.

System scaffold

<figure>
  <img src="https://scaffoldoptix.co.uk/glossary/system-scaffold/diagram.svg" alt="system scaffold — scaffold diagram from ScaffoldOptix" width="880" height="620" loading="lazy">
  <figcaption>
    <a href="https://scaffoldoptix.co.uk/glossary/system-scaffold">What is a system scaffold?</a> — diagram by
    <a href="https://scaffoldoptix.co.uk">ScaffoldOptix</a>
  </figcaption>
</figure>

Prefabricated components connecting at fixed positions, through rosettes or cups welded to the standards. Faster, more consistent, fewer loose fittings — and fixed to whatever geometry the system allows.

Systems are not interchangeable between manufacturers. Mixing components across systems is a real hazard rather than a theoretical one, because connections may engage without achieving the performance the design assumed.

Which type do you actually need?

In practice the type is chosen by elimination rather than selection, and the questions run in this order.

• –Is there ground to stand on? If not, you are into cantilever, truss-out, suspended or bridged territory, and into bespoke design.
• –Are you working along a face, or over an area? A run of elevation is a facade scaffold; a ceiling or floor area is a birdcage.
• –Is it a run or a point? One spot at height is a tower, not a scaffold run.
• –What is landing on it? Material arriving by crane means a loading bay designed for it, not an ordinary bay used for it.
• –What is underneath? A public footway means a gantry, a fan, or both, and a highway licence.
• –How long, and in what weather? Sheeting and temporary roofs change the loading enough to change the tie pattern and often the design.

Who decides, and what gets recorded

For ordinary facade and access scaffolds within the usual configurations, TG20 answers it and the compliance sheet is the record. For anything else — cantilevers, truss-outs, temporary roofs, bridged sections, suspended access — the answer comes from a temporary works designer working to a design brief, and the design is the record.

Whichever it is, the thing that matters six months later is whether the record is attached to the structure. A compliance sheet in an inbox and a design in a folder are both evidence nobody can find when a client asks what a standing scaffold was built to. Holding it against the structure is the difference between answering that in seconds and answering it in an afternoon.

Every diagram on this page is free to use on your own site or in training material with a credit link — the snippet is under each one. The full scaffolding glossary covers ninety terms the same way.

Common questions