Scaffolding and roofing contractors: the wind call, at your height

As a scaffold contractor owner-director or roofing foreman, you make the call daily: can the crew erect, strike, sheet, or lay roofing today? This decision often needs to be made overnight, especially before forecast gales. You need to know if a sheeted scaffold requires strengthening or if it is suitable for work.

Your decision is critical. A wrong call can lead to lost crew days if scaffolding needs post-storm inspection before reuse. More gravely, a scaffold collapse could occur, as happened in Dublin during Storm Éowyn in January 2025. Such incidents can result in significant liability and third-party damage.

Your primary concern is knowing, often by 5 am, whether your gang can suitably go up on a sheeted lift. You also need to know when to strike or add ties to a scaffold before a gale hits, rather than reacting after the fact. This requires precise wind information at your working height, not just ground-level forecasts.

The instrument helps you make these daily decisions. It provides the specific wind data you need to assess the risks, giving you a clear picture of conditions at your working height. This allows you to make informed decisions about crew deployment and scaffold integrity, helping to prevent costly downtime and potential collapses.

Your work, whether on a roof or a scaffold, means you are concerned with wind at height, not at ground level. The instrument focuses on the wind at your working height, interpolating between standard model heights of 10, 80, 120, and 180 metres to give you a precise reading for your specific work.

For scaffolding and roofing, the critical measurement is often the gust at roof or top-lift height. A mean wind speed might seem acceptable, but a sudden gust can exceed your operational limit and create dangerous conditions. The instrument displays gusts alongside the mean wind speed, ensuring you have a complete picture of the forces acting on your structure.

Your operational limit for wind is set by your own documents, such as TG20 design guidelines, sheeting supplier instructions, or the HSA code of practice for access and working scaffolds. For example, the HSENI cites 10.3 m/s (23 mph, Force 5) for roof and edge work. You enter this specific limit into the instrument.

Any height below 10 metres is extrapolated from the lowest model level and is clearly badged as such. This distinction is important because wind behaviour close to the ground can differ significantly from wind at height, where your crews are working.

The instrument provides the odds, expressed as P(above your limit), by the hour. This is the fraction of ensemble members that predict wind speeds above your set limit at your working height. These ensemble members are derived from models at 10, 80, 100, and 120 metres, giving you a probabilistic view of future conditions.

For example, if 20 per cent of ensemble members show wind above your limit, you might proceed with caution, ensuring all ties are secure and materials are battened down. If 50 per cent show wind above your limit, you would likely delay sheeting operations or consider strengthening measures. At 80 per cent, you would almost certainly stand down the crew for work at height, as the risk of exceeding your limit is high.

The Agreement Spine on the instrument shows where different weather models agree and where they do not. High agreement among models provides more confidence in the forecast. If models disagree significantly, it indicates higher uncertainty, prompting you to be more vigilant and potentially more conservative in your decisions.

Understanding these odds allows you to make a more nuanced decision than a simple 'go/no-go'. It helps you assess the likelihood of exceeding your wind limit and take appropriate actions, such as adjusting your work plan or implementing additional measures, to protect your crew and your structures.

This is an example of how you might use the instrument in your daily operations:

• 04:30: You check the instrument before the crew arrives. For your 20-metre working height, the forecast shows P(above your limit of 10.3 m/s) at 20 per cent for the morning, rising to 60 per cent by 14:00. Gusts are forecast to reach 15 m/s by mid-afternoon.
• 05:00: You decide the crew can start work on the sheeted lift, but you plan to bring them down by 13:00. You also instruct the foreman to check all scaffold ties before the afternoon.
• 08:00: You review the forecast again. The odds for the afternoon have increased to 70 per cent, and the Agreement Spine shows increasing model consensus on higher winds. You confirm the plan to finish work at height by 13:00.
• 11:00: You notice a significant shift in the forecast: P(above your limit) for 14:00 is now 85 per cent, with gusts potentially reaching 18 m/s. You decide to bring the crew down immediately and instruct them to secure all loose materials.
• 13:00: The wind picks up as forecast. Your crew is suitably on the ground, and the scaffold is secured. You can now record this decision.

This example demonstrates how the instrument allows you to monitor conditions and adjust your plans in real-time, based on the evolving wind forecast and the associated risks.

Your operational wind limit is a critical input for the instrument. This limit does not come from the instrument itself, but from your own project documentation, industry standards, or regulatory guidance. It is the maximum wind speed, often a gust, at which it is suitable to carry out specific tasks or at which a scaffold remains stable.

For scaffolding and roofing contractors, this limit is typically derived from sources such as TG20 design guidelines, specific instructions from sheeting suppliers, or the HSA Code of Practice for Access and Working Scaffolds. For instance, the HSENI has cited 10.3 m/s (23 mph, Force 5) for roof and edge work. You will type this exact value, specific to your operation and the relevant metric (e.g., gust at roof or top-lift height), into the instrument.

The instrument comes with a preset height of 20 metres and a limit of 23 mph (10.3 m/s) for gust at roof or top-lift height, which aligns with common industry practice for your work. However, you can adjust this to precisely match the requirements of your specific job and the height your crew is working at.

By accurately setting your limit based on your own documents, you ensure that the instrument's P(above your limit) calculations are directly relevant to your protocols and operational thresholds. This tailored approach helps you make informed decisions that are consistent with your established practices.

The instrument maintains a dated record page of what was forecast, what was observed, the limit you used, and the call you made. This record is more than just an archive; it is a vital tool for accountability and continuous improvement in your operations.

When incidents occur, or when questions arise about operational decisions, having a clear, immutable record is essential. If a scaffold is damaged during a storm, or if there is an inquiry into why work was halted, this record provides objective evidence of the information you had at the time and the basis for your decision to proceed or stand down.

This record also serves as proof that you acted responsibly, particularly if you stood down your crew due to high winds. It demonstrates due diligence and adherence to protocols, which can be important for insurers or regulatory bodies. It confirms that you had access to wind data at your working height, not just ground-level information, and that you made a considered judgment based on that data.

Over time, reviewing these records can help you refine your decision-making processes. You can compare forecasts with actual observations and see how your calls aligned with the instrument's information. This feedback loop can enhance your understanding of wind conditions and improve your future operational planning.

Ireland's geographical position means it is particularly exposed to Atlantic weather systems, making accurate wind forecasting critical for scaffolding and roofing contractors. The storm season, typically running from October to March, brings frequent gales that can significantly impact work at height.

During these months, and especially for sheeted facade jobs in the summer, understanding wind conditions at height is paramount. Ground-level forecasts from Met Éireann, the national forecaster, provide a general picture, but your work requires specific data for your elevation.

For example, the aftermath of Storm Éowyn in January 2025 highlighted the vulnerability of structures like scaffolding to high winds. Such events underscore the need for precise, height-specific wind information to prevent damage and ensure the well-being of your crew. The instrument provides this focused data, helping you to manage the risks associated with Ireland's often challenging weather conditions.

By using the instrument, you can better prepare for and react to the strong winds common in Ireland, ensuring your operations continue efficiently and without undue risk. This local context makes precise wind data at height particularly valuable for contractors operating across the country.