Storm Austen produced an official UK peak gust of 76mph on 23 October, while strong winds and rough seas also brought down another section of Brighton’s West Pier. For construction teams, however, the useful engineering question is not whether a temporary structure should simply be designed for 76mph.
The Met Office recorded 76mph at St Mary’s Airport on the Isles of Scilly, 75mph at Portland and the Needles, and 74mph at Aberporth. Those are meteorological observations at particular locations. A temporary works design, by contrast, derives wind actions for the structure actually being built, taking account of its location, height, terrain, geometry, exposure, configuration and intended period of use.
Brighton provides a timely illustration of the forces involved, but not a temporary works failure case study. The West Pier Trust describes the 1866 pier as a historic ruin that has been in a state of active collapse for decades following long-term deterioration and the 2003 fires. Its latest loss during Storm Austen should therefore not be used to infer anything about the adequacy of temporary works design.
LCM has already examined the immediate operational checks required across construction sites during Storm Austen and Storm Boelo. The deeper temporary works issue is what sits behind those checks: how wind enters the design, what assumptions the engineer has made, and what happens when the arrangement on site no longer matches those assumptions.
Tower cranes and temporary works on a steel-frame construction project in London. Wind design depends on the structure, exposure, height, configuration and site-specific conditions rather than a headline weather gust alone. Photo: London Construction Magazine.
Key Takeaway: A forecast or recorded gust cannot be compared directly with a temporary works design wind speed. The engineering check depends on the design basis, site exposure, structure geometry, duration, restraints and the actual configuration standing on site.
Why a 76mph Gust Is Not a 76mph Design Check
Weather forecasts and structural wind design answer different questions. A Met Office gust describes atmospheric conditions observed or forecast at a location. Structural design converts an established wind climate into pressures and forces acting on a particular structure, with adjustments for the site and the form of the temporary works.
This distinction matters when a storm approaches and somebody asks whether a scaffold, hoarding or temporary roof is rated for 70mph. Without the design basis, that number tells very little. The designer may have considered a different reference wind parameter, height above ground, terrain roughness, topography, shielding, neighbouring buildings, exposed area and aerodynamic behaviour before arriving at the forces used for the structural check.
| Question | Weather Forecast or Observation | Temporary Works Design |
|---|---|---|
| What does the number represent? | Meteorological wind conditions at or around a forecast or observation point. | Code-derived wind actions applied to a particular structure and configuration. |
| Does location matter? | Yes. Gusts differ as a storm moves across the country. | Yes. Site location, terrain, altitude, topography and surrounding development can all affect the design. |
| Does the structure matter? | No structural capacity is implied by the forecast itself. | Yes. Height, exposed area, porosity, geometry, ties, anchors, foundations and bracing are fundamental. |
| Can the two figures be compared directly? | No. The design information and current site configuration have to be reviewed before an engineering judgement can be made. | |
What the Temporary Works Designer Actually Has to Consider
Wind design begins with the geographic wind climate but quickly becomes site-specific. The applicable Eurocode procedure considers exposure and terrain, while temporary works guidance adds the practical conditions that can make one arrangement behave very differently from another only a short distance away.
Height is one of the obvious variables. Conditions acting on the upper lifts of a tall scaffold or a high temporary roof are not necessarily represented by what site personnel experience at ground level. Topography can also accelerate airflow, while neighbouring buildings may shield one elevation but create turbulence or funnelling through gaps elsewhere.
That local behaviour has become more explicit in the current temporary works standard. BSI’s summary of BS 5975-2:2024 specifically identifies the effects of adjacent tall structures, funnelling through terrain or buildings and susceptibility to vortex shedding among the additions to the revised falsework standard.
The physical form of the temporary works is equally important. An open scaffold, a scaffold carrying debris netting and a fully sheeted scaffold are not aerodynamically equivalent. HSE guidance is explicit that sheeting or debris netting should not be attached without informing those responsible for the scaffold design because the structure must be suitable for the resulting condition.
The same principle applies to hoardings, temporary roofs, façade retention, formwork and other large exposed surfaces. The Temporary Works Forum’s hoarding guidance treats hoardings as engineering structures capable of attracting significant loads and specifically identifies duration, shielding and wind effects around tall buildings as design considerations.
BS 5975 Changed in 2024, Including Its Treatment of Wind
The temporary works framework itself has changed. The former BS 5975:2019 has been replaced by BS 5975-1:2024 for temporary works management procedures and BS 5975-2:2024 for falsework design and implementation. That distinction matters when project documentation, design briefs or procedures still refer generically to the older single-volume standard.
For falsework, BSI says the 2024 revision calculates maximum wind forces on a likely erection duration of one year, reduced from two years, with a ten-year return period. That is a probabilistic design basis appropriate to the defined temporary condition; it is not a universal operating threshold for every temporary structure on every site.
Short exposure duration does not mean wind can simply be discounted. Institution of Structural Engineers guidance notes that temporary structures may be less likely to experience the characteristic wind event used for permanent structures and that probability or seasonal factors may therefore be applicable, but it also cautions that reductions require careful consideration.
There is an additional standards transition underway. BS EN 1991-1-4:2026, the second-generation Eurocode for wind actions, was published in June. BSI nevertheless states that first-generation Eurocodes remain the applicable standards for UK buildings and civil engineering works until 30 March 2028 unless a relevant authority or project specification requires otherwise. Designers therefore need to establish the project’s actual code basis rather than assume that the newest publication automatically replaces the existing UK design framework.
The Design Is Only Valid for the Arrangement It Checked
A structurally adequate design can still be undermined if the temporary works standing on site no longer match it. This is where storm preparation becomes as much a temporary works management issue as a structural calculation issue.
A scaffold originally designed as an open arrangement may later acquire sheeting, netting or advertising banners. Ties may have been temporarily removed to allow façade installation. Hoarding panels may have been altered for access. Materials may be stored on platforms that were never intended to carry them. Demolition can remove a building or façade that previously provided shielding. Each change can alter the condition assumed by the original design.
HSE states that temporary structures must be designed, installed and maintained to withstand foreseeable loads. Its scaffolding guidance also requires ties to remain within their safe working limits and says scaffolds should be checked whenever they are substantially altered or adversely affected, including by high winds.
That is why the Temporary Works Coordinator needs more than tomorrow’s weather forecast. The useful question is whether the current temporary works register, approved design, inspection status and site configuration still describe the same structure. LCM’s analysis of BS 5975 temporary works change control examines the wider problem: apparently small changes can alter a load path or stability mechanism and invalidate the assumptions behind the checked design.
Before severe wind arrives, that review should identify temporary works particularly exposed to wind, confirm that ties, bracing, anchors and foundations remain as designed, establish whether sheeting or other surfaces have changed, secure loose materials and follow any structure-specific or manufacturer operating restrictions. NASC SG46:24 addresses weather-related risk assessment, stopping and resuming scaffold operations, inspection requirements and securing structures during adverse conditions.
After the Storm, Inspection Comes Before Normal Use
The end of a weather warning does not automatically return temporary works to their pre-storm condition. HSE requires scaffolding to be inspected after circumstances liable to jeopardise its safety, explicitly giving high winds as an example. The inspection must be carried out by a competent person appropriate to the type and complexity of the scaffold.
The physical inspection should be appropriate to the temporary works involved. On scaffolding that can include ties, bracing, platforms, sheeting, base plates, sole boards and evidence of movement or settlement. Heavy rain accompanying a storm may also change ground conditions beneath foundations or supports even where the wind has caused no obvious damage above ground.
Where a design assumption has changed, the issue should move back through the project’s temporary works procedure rather than being resolved informally on site. The same principle applies where damage, partial dismantling or altered restraint leaves the installed arrangement different from the approved design. LCM’s BS 5975 temporary works guidance sets out the wider relationship between the design brief, checking, implementation, inspection and permit controls.
Storm Austen’s 76mph observation is therefore useful context, but not an engineering pass-or-fail number. The relevant question on a construction site is whether the temporary works standing there are the arrangement that was designed and checked, whether the design basis remains appropriate for the exposure, and whether the structure has been inspected before normal use resumes.
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Founder & Author, London Construction Magazine | Construction Testing & Investigation Specialist