Adverse weather in construction contracts

Adverse weather in construction contracts

Adverse weather in construction contracts

As storms and snow continue to batter parts of the UK, you only have to look at the news (or be a frequent passenger on Britain’s railways) to understand the disruptive effect intense weather can have on day-to-day life. It would be wrong however to suggest these intense periods of weather are limited to these winter months. The Summer of 2019, for example, was the hottest in 140 years, leading to water shortages, buckling railways and melting roads across the country. No matter the season, weather remains an ever-present risk to the well-laid plans of individuals and businesses alike.

Given the potentially delaying effect weather can have on a construction project, it is perhaps unsurprising that many standard forms of building contract take steps to account for this. Yet, while many allow for additional time where weather is found to have impacted the works, there remains a lack of consistency within the industry as to what exactly constitutes ‘adverse weather’ and the likelihood that a contractor will be compensated for any delay.

We will look briefly at a few standard building contracts, how they account for the risk posed by adverse weather and some common issues which can arise under these contracts in respect of this.

JCT Contract 

The JCT suite of contracts simply state that “exceptionally adverse weather conditions” are relevant events under the contract. No further information is provided to specify what exactly constitutes exceptionally adverse weather however, making it challenging for the parties to determine if the requirements of the relevant event have been fulfilled. Given these difficulties, it is perhaps unsurprising that some contracts seek to remove adverse weather as a relevant event altogether.

Should the option remain, the contractor will be required to provide a notice to the architect, contractor administrator or employer as soon as they are aware of the impact (or likely impact) the weather will have to the completion of the works. As part of this notice, the contractor will need to detail the circumstances surrounding the delay and may, depending on the contract terms, be required to provide an estimate as to the extent of the delay caused by the weather event. Additional notices may also need to be served where there are changes to this estimate.

The difficulty for a contractor in these circumstances will be providing sufficient evidence to justify an extension of time being granted. The JCT however have taken steps to assist contractors with this issue by working alongside the Met Office to provide ‘JCT Met Office Weather Reports’. Of these reports, the ‘Downtime Report’ can prove particularly helpful as it is designed specifically to set out location specific information including whether certain weather values are less or greater than a 1-in-10 year value. Given the need for the weather to be “exceptionally adverse” these figures can prove helpful in justifying a contractor’s claim.

Despite the assistance granted by these reports, the risk remains that with such a broad definition, contractors cannot guarantee that any application for additional time will be accepted under the JCT contract.   

NEC Contract

In contrast to the JCT, the NEC suite of contracts provides a detailed description of what constitutes adverse weather. In order for the compensation event to be granted, the weather measurement in question must be recorded:

  • within a calendar month of the compensation event;
  • before the Completion Date for the whole of the works; and
  • at the place stated in the Contract Data.

Once this weather is recorded, the value must be compared with the weather data, this being historic records of weather in the local area. If the weather measurement is subsequently found to occur on average, less than once in ten years then a compensation event will be found to have taken place and an extension of time awarded accordingly.

The NEC sets out in its contract data that weather measurements for each month are to be made based on:

  • cumulative rainfall;
  • the number of days with rainfall of more than 5mm;
  • the number of days with a minimum air temperature of less than 0 degrees Celsius; and
  • the number of days with snow lying on the ground at a set time.

While additional measurements can be stipulated within the contract, it is worth noting that the NEC fails to address other adverse weather conditions such as heatwaves and high winds. Even if this were to be the case, evidence would need to be provided to the project manager showing that these weather events occurred on average, less than once in ten years.

As a result, while the NEC Contract clearly sets out what constitutes adverse weather conditions, the fact remains that the threshold for achieving the requirements are considerably higher than under a JCT contract. Contractors therefore need to be alert to the possibility that, despite potentially intense and disruptive weather, they may not be awarded with the additional time and costs that they seek.

FIDIC Contract          

The FIDIC suite of contracts states a contractor may be entitled to an extension of time where a delay is caused due to:

exceptionally adverse climate conditions, which for the purpose of these Conditions shall mean adverse climatic conditions at the Site which are Unforeseeable having regard to climatic data made by the Employer…and/or climatic data published in the Country for the geographical location of the Site.”

At first glance, this clause appears to occupy a middle ground between the JCT and NEC provisions for adverse weather. While the definition of “exceptionally adverse climate conditions” appears to be broad, this does allow for various types of weather, such as heatwaves and snowstorms, to be accounted for. Similarly, by requiring these climate conditions to be measured against climate data made by the employer or published in the country for the geographical location, it is possible to quantify whether the climate condition is “exceptionally adverse”. The threshold for achieving this also appears to be lower, as the contractor is not required to prove that the adverse weather itself occurs on average less than once in ten years. It would therefore appear that this clause strikes a balance between being both broadly defined and quantifiable.

It should be noted however that, under the FIDIC contract, where a delay is concurrent with a delay caused by the contractor, then the contractor’s entitlement to an extension of time shall be assessed in accordance with the rules and procedures stated in the Special Provisions. It is therefore possible that, even where a contractor is entitled to an extension of time resulting from adverse climate conditions, they will still not be awarded this if it is concurrent with another delay caused by them. Contractors need to be aware of this risk when looking to apply for an extension of time accordingly. 

The Singapore SIA Contract: A Balanced Approach?

Within his textbook, ‘Construction Contracts: Principles and Policies in Tort and Contract’, Ian Duncan Wallace sets out their own proposed wording for when adverse weather might lead to an extension of time under the Singapore SIA Contract:

Exceptionally adverse weather conditions (in assessing the same regard shall be hard to meteorological averages, the reasonable expectation of adverse conditions both seasonal and annual during the contract period, and to the net effect overall of any exceptionally beneficial conditions as well as the immediate effect of individual instances of exceptionally adverse conditions).”

This wording adopts a balanced approach, being both broadly drafted to allow for all forms of adverse weather while clearly establishing the evidence necessary for an extension of time to be granted. Beneficial weather conditions are also taken into effect when calculating any additional time that may be awarded.

Where a contractor has concerns that adverse weather may affect the works, wording similar to this may be preferable in order to give both party’s clarity and certainty moving forward.


While what constitutes ‘adverse weather’ varies depending on the form of building contract, it remains vital that contractors are alert to the following:

  • the need to maintain comprehensive records of the weather on site - these need to be updated regularly if the contractor is to rely on them as evidence that the weather has negatively impacted the progress of works;
  • what adverse weather is covered by the contract – not all building contracts cover all types of weather. Similarly, the building contract may set out a strict baseline for what constitutes ‘adverse weather’. Contractors need to be aware of these restrictions and, if necessary, request amendments to the contract to take into account the weather conditions likely to affect the works being carried out; and
  • ensure compliance with the contract terms, particularly surrounding notices – like any application for an extension of time or additional costs, the contractor must ensure they comply with any provisions surrounding the service of notices and the information required as part of weather, an extension of time will not be granted.  

While it can often be difficult to plan for the weather over the course of a construction project, contractors can take active steps to ensure that their contract gives them the security they need to ensure that, should any adverse weather arise, they will be able to weather the storm of delays and disruption that follow.

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