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Construction Contracts and Adverse Weather

Wind weather planning: Before, during and after

Dealing with weather-related claims in construction contracts and Extension of Time using site specific wind data at crane height

scaffolding-collapse-due-to-high-winds.jpegWeather is a critical factor in construction design, planning and execution has among the most varied and far-reaching effects on project outcome.

It is one of the most frequent and harmful causes of project delays and weather claims are a frequent cause of dispute between contractors and owners. These disputes can escalate into legal action, extended delays and further economic losses.

Just one serious weather event leading to a day of lost work on a $200M project could cost a construction company $250 K directly from its profit. (1)

The UK weather extends project durations by 21% on average, compared with the baseline. (2)

How is best to deal with the threat of adverse weather?

The key advice here falls into three categories: planning, notices and record-keeping.
These could equally be referred to as before, during and after.

Before (planning)

Programmes should make allowances for weather conditions. This requires good risk management and risk knowledge. Extensive, local weather data helps bidding teams and construction site managers plan more effectively, accurately and profitably by:

  • Creating weather monitoring plans and routines
  • Connecting weather predictions to possible exposures in your project schedule
  • Preparing people. Contractors should take the time to discuss weather possibilities and action plans with all personnel.
  • Developing communication and notification plans. Plans should outline how the project team will communicate weather warnings and alerts to everyone working on the site, as well as offsite stakeholders (owner, architects,
    engineers, subcontractors' offices, etc.)

During (notices)

It is essential that weather forecasts and actual conditions are continuously monitored. Contracts are likely to require the contractor to give notices to the employer if adverse weather (or anything else) is likely to cause a delay to project completion. The contractor should ensure that the notices are given in accordance with the timing and details required, to the people specified under the contract. Detailed weather forecast data through out the contract can aid in:

  • Revisiting the possible exposures identified in the project schedule and action plans for severe weather.
  • Painting an accurate meteorological picture to connect the current status of construction sites with possible weather events, and update action plans accordingly.
  • Communicating weather warnings and alerts to everyone working on the site, as well as offsite stakeholders (owner, architects, engineers, subcontractors’ offices, etc.)

After (record keeping)

Weather claims are a frequent cause of disputes, often escalating to legal action and extended delays. Construction contracts have penalties called liquidated damages, which are paid by the contractor to the client when the deadline is missed. However, if a project is delayed by extreme or unforeseeable weather, the contractor can request an Extension of Time (EoT) to be waived from financial penalties.

  • When adverse weather conditions do strike; accurate, site-specific and detailed records are essential.

How bad does the weather have to be to be?

Blog - Weather.jpgIn terms of building contracts, weather events are usually classified as:

  • Foreseeable VS Unforeseeable
  • Extreme VS Non-extreme

Taking this last point, in some cases delays can be so sizable and excessive due to adverse weather that ‘force majeure’ may be indicated as the cause of the delay. Force majeure, sometimes referred to as the Act of God clause, it is a failure to uphold a contract due to unavoidable or uncontrollable events like extreme weather events. (3)

However, Foreseeable vs Unforeseeable is not so self-evident. Most construction contracts use the term 'exceptionally adverse' weather conditions (or similar), but not all will accurately define it.

For example, NEC engineering contract refers in clause 60.1(13) to weather events which are shown to occur on average 'less frequently than once in ten years'.
Similarly, previous case law for JCT contracts often refers to 10 years of previous meteorological records for sites as the frame of reference within which to argue. (4)

Construction projects can be affected by many weather conditions, but the wind requires special attention. It can change rapidly and without warning, and gusts can lift materials and even equipment. In extreme cases, strong wind may cause the collapse of cranes or structures in progress, but even gusts of 30knots / 15.4m/s / 34.5mph or more can delay activities like concrete pouring, form-works, scaffolding, steelworks and outdoor painting.

Using historical data as the base point, if a contractor has access to detailed and accurate on-site records they can demonstrate that X hours of wind above this level in a certain month is “exceptional”, allowing the contractor to evidence a claim for extension of time.

How is best to access and record site weather data?

Solely relying on a Met Office weather warning for weather conditions which are likely to cause delay (such as snow or wind) in the relevant area will not be sufficient to protect against the weather. In terms of claims, weather forecasts don’t provide enough proof by themselves to justify a weather claim. Consider that a weather forecast is a prediction, not measured data. Without actual measurements, a contractor cannot prove that weather conditions at the project were unsafe for construction work.

However, even forecasts and readings provided by local weather stations are not fully accurate. In terms of wind data in particular, ground level measurements at the construction site do not reflect actual conditions for tall structures and cranes. A weather station on a 10m pole does not reflect wind conditions for a 250m tower crane. Wind speeds increase with altitude, as the wind is disrupted by obstacles at ground level.

To justify a suspension of lifting activities, there is no better evidence than measuring the wind directly at the crane. WINDCRANE wind monitoring provides accurate wind data specific to the location and height for construction cranes.

Before (planning)

WINDCRANE enables planning the optimal time for crane lifting and site operations using SPECIFIC FORECASTING from wind speeds that are supported by the exact localised wind data from within the crane at the exact operating height, and not a prediction from a nearby weather station.

During (notices)

WINDCRANE provides LIVE WIND SPEED RISK OVERVIEW, supporting the safety of your personnel and equipment by reducing unnecessary risks with LIVE wind speed data and alert notifications.


After (record keeping)

WINDCRANE provides DOWNTIME WIND REPORTS using accurate HISTORICAL measurements from the exact crane height. Reduce weather disputes by recording and demonstrating accurate WIND SPEED DATA.

Windcrane Weekly Historical Report.png

In summary; site specific weather forecasting, continuous monitoring and recording of weather data is essential FROM PLANNING RIGHT THROUGH TO PROJECT COMPLETION.

WINDCRANE provides historic, live and recorded wind data and reports specific to crane site and height: Solid evidence to back claims for delays due to ‘unforeseen’ and ‘exceptional’ weather conditions.

(1) Weather assessment solutions in construction
(2) Construction Management and Economics Journal
(3) Extreme weather the construction industry costs
(4) Construction contracts adverse weather

Do you need to measure and record wind speed? 

Windcrane has compiled various kits depending on your project application, visit:

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