What is a “bridge” vs a “pavement gantry”?

Bridging scaffold: a scaffold arrangement that spans over an obstruction (glass roof, conservatory, canopy, alley, lower roof, plant, a void, etc.) rather than bearing to the ground continuously.

Pavement gantry (often called a pedestrian gantry): a structure that provides a protected walkway for pedestrians under/through scaffold works (and sometimes carries site accommodation/storage over the highway, depending on the local authority definition).

Design considerations that matter (and why)

1) Load path and span behaviour

Once you bridge, you’ve created a set of members that act like beams/girders, meaning:

• concentrated reactions at supports,

• deflection control becomes important (not just strength),

• and stability/bracing demands often increase because the scaffold becomes “less redundant.”

In practice, bridging often forces a bespoke design approach because the structure is no longer a standard access scaffold arrangement.

2) Foundations and what’s really under the pavement

Pavements are notorious for hiding:

• basements/vaults and cellars,

• service corridors and ducts,

• fragile slabs, manholes, legacy structures.

Local highway licence criteria often include minimum offsets from kerb lines and clearance heights, and may require pedestrian gantries to be designed.
If you can’t rely on uniform ground bearing, you may need spreaders/grillages or an altered layout to avoid point loading vulnerable zones.

3) Public protection requirements

Where the public pass underneath, the scaffold has to address:

• falling object risk (caps/low-level protection, fans, debris control),

• protected headroom and clear widths,

• safe segregated erection/dismantle, often with temporary closures or traffic management.

HSE emphasises public protection and segregation when scaffolding operations could endanger pedestrians.
Some council protocols explicitly call for overhead coverings/fans/netting/sheeting for public protection on highways.

4) Stability, ties, and “don’t touch that”

Bridging/gantries usually have fewer natural restraints, so stability is heavily dependent on:

• tie strategy,

• plan bracing,

• buttressing/rakers (where ties are restricted),

• and controlling alterations.

HSE’s scaffolding guidance is explicit: scaffolds must be tied/braced/stabilised and ties managed properly.
On public interfaces, uncontrolled changes are especially risky: if someone removes a tie for access, the consequences aren’t “internal” — they’re public-facing.

5) Clearance heights, widths, and interfaces

Approvals often hinge on basics:

• clear headroom (often referenced around ~5.05m near carriageway in some licence criteria, measured from kerb/road level),

• keeping scaffold a minimum distance from carriageway edge where practicable,

• maintaining pedestrian route widths and accessibility.

These aren’t “nice to haves”—they’re licence conditions in many boroughs and highways authorities.

Approvals and paperwork: what usually applies

1) Highway / local authority licence

If you’re placing scaffolding/gantries on or over a public highway, you generally need a scaffolding/hoarding (highway) licence from the relevant local authority.
Licences frequently include conditions on:

• working hours for erection/dismantle,

• lighting,

• pedestrian management,

• insurance levels (often high—e.g., some councils specify £10m public liability).

2) TfL approvals (Red Routes)

If it’s on a TfL Red Route, you may need a TfL highway licence rather than (or in addition to) the borough’s process. TfL explicitly issues highway licences for items including scaffolds.

3) Traffic management / closures

Where erection/dismantle risks the public, HSE points to considering footpath/road closure and segregation.
Many licence application packs prompt for whether closures are required during erection/dismantle and require a traffic management plan where relevant.

What we need from you (so we can design it and get it approved)

To design a bridge or pavement gantry without a redesign loop, send:

Site + authority

• Exact address + borough/highway authority (and whether it’s a TfL Red Route)

• Any known licence conditions or required clear widths/heights (if already issued)

Geometry

• Span length(s) and what you’re spanning over (glazing, canopy, alley, entrances)

• Required pedestrian clear width and headroom

• Scaffold heights, returns, and any offsets/setbacks

Ground/support constraints

• Any basements/vaults/ducts/manholes in the footprint

• “No-load” zones or slab limits (especially common in city centres)

Loading and use

• Access only vs storage

• Any hoists/loading bays/signage

• Any sheeting/netting/wrap (wind area)

Public protection

• Required protection level: fans/decks, debris control, lighting, signage

• Erection/dismantle plan assumptions (closures, segregation)

Common failure points (seen too often)

• Designing a bridge like a normal bay (ignoring transfer actions and deflection)

• Unknown vaults/services → support locations become “not permitted” mid-erection

• Public route narrowed/poorly protected → licence non-compliance and reputational risk

• Late add-ons (sheeting, signage, loading points) → stability and approvals need review

• Uncontrolled alterations → the designed stability system is quietly dismantled by “site convenience”

Practical closing thought

Bridging and pavement gantries are where scaffold design stops being “access” and becomes temporary works engineering with public risk and approvals attached. If you treat the authority requirements, the ground conditions, and the stability system as first-class design inputs from day one, you’ll save yourself the usual trio of pain: redesigns, licence delays, and on-site improvisation.