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Construction projects and adverse conditions: What are the rules?

21 February 2020 #Construction

Whilst it’s not unusual for adverse weather to affect the UK, it always seems to come as something of a surprise to us. However, what does ‘adverse weather’ actually mean in law? How do you determine any entitlement to money or time? And what should you do if your project suffers delay as a result of bad weather?

Construction projects are often victims of the elements and determining where risk lies can be a major cause of disputes. Adverse weather may entitle a contractor to an extension of time or compensation, depending upon the contract terms. However, correct identification and notification of delay and disruption are crucial to ensuring entitlement.


The JCT suite of contracts class ‘exceptionally adverse weather conditions’ as a Relevant Event. This has the potential to entitle you to an extension of time. Unfortunately, the JCT do not define what ‘exceptionally adverse weather conditions’ are, and there seems to be no generally accepted definition. Generally, courts and tribunals refer to adverse weather as weather which exceeds the long-term average for the time of year and location.

In Walter Lawrence & Son v Commercial Union Properties, the court made clear that the weather must be exceptional. In that case, the court referred to Meteorological Office records going back 30 years to make this assessment. Additionally, the analysis of the adverse conditions was carried out when the works actually took place, not when they were scheduled to do so.


Under NEC contracts, adverse weather can be treated as a Compensation Event. In contrast to the JCT, NEC does provide a definition for such conditions. NEC defines adverse weather as weather which on average occurs less than once in ten years within that calendar month. The exact definition is found in Clause 60.1(13) and is quite precise in setting out that only the difference between those conditions that ought to have been reasonably allowed for, and a ten-year event are classed as ‘adverse weather’.

Given the above, would a storm in February count as adverse weather? If your project has suffered delay and disruption, what steps should you take?

Check the Contract and Keep Records

In most construction contracts, the contractor will bear the risk of any disruptive weather that falls outside these definitions. It is important that before entering into any contract, you have understood the allocation of risk. If the contract is silent on weather, the contractor may be responsible for the risk, no matter how bad the weather.

Another consideration may arise if the adverse weather occurs after the contractual completion date of the construction project. In such cases, the contract may not allow for any extension of time or compensation. Again, this will need to be checked with the exact terms of the contract.

Whatever the form of contract, the first steps you should take are to follow the notification procedures set out in your contract. Record and notify within any required timeframes the full details and impact of any adverse conditions that might comply with definitions prescribed in your contract. Ensuring you comply with your obligations under the contract is critical for success.

A major difficulty with disputes arising from weather conditions can be assessing the impact on the delay. Therefore, it is important that you keep project records accurate and up to date in a form that will enable you to demonstrate the link between cause and effect. Be sure to record any impact the weather has on progress.

You must be able to show that the weather caused a delay. If you cannot show the delay was caused by the weather conditions, you will not be able to claim. Under JCT, if you can demonstrate this delay, you will be able to claim for an extension of time, but not for money. NEC, in contrast, does allow you to claim for time and money.

Clarkslegal, specialist Construction lawyers in London, Reading and throughout the Thames Valley.
For further information about this or any other Construction matter please contact Clarkslegal's construction team by email at by telephone 020 7539 8000 (London office), 0118 958 5321 (Reading office) or by completing the form on this page.
This information is for guidance purposes only and should not be regarded as a substitute for taking legal advice. Please refer to the full General Notices on our website.

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Stephen James

Stephen James

T: 0118 960 4674
M: 07884 188 021


Construction team
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