The brief but unprecedented heatwave, in excess of 40°C, in July 2022 had a severe impact across the construction sector. Industry giants Sir Robert McAlpine and Laing O'Rourke confirmed their sites could be closed and work stopped to safeguard the welfare of staff working outside. If extreme heat impedes progress and a Contractor anticipates delays to the Completion Date, can it claim for an extension of time?

JCT Contracts 2016

The JCT Contracts 2016 entitle a Contractor to an extension of time for Relevant Events which include exceptionally adverse weather conditions.[1] This is not a Relevant Matter, which would entitle the Contractor to recover loss and expense.

The term exceptionally adverse weather conditions is not defined. Its meaning will differ depending on the type of project, location, effect on progress, and weather severity. Traditionally, (in the 1963 JCT contract), this ground was called inclement weather, and was envisaged to be poor conditions e.g. rain and snow.[2]

The definition does not refer to any specific metrics. Instead it relies on the principle that words in a commercial agreement should take their ordinary meaning. Data would be needed to demonstrate greater than usual adverse conditions. This means much more than average, at the specific site location, at the time rather than when works were programmed, to be contrasted with historic weather conditions.

Contractors can support their Relevant Event claims using weather reports the JCT have created in collaboration with the Met Office:

  • A Weather Planning Report – created for project planning to consider one in 10 year and long term average conditions for weather such as: daily rainfall totals; rain above 5mm; snow; ground frost; freezing; and hours of total sunshine
  • A Downtime Report – created for post project management to consider one in 10 year and long term averages for weather such as: monthly rainfall, rain above 5mm, snow, ground frost, freezing, total monthly sunshine hours and total monthly solar radiation.

To make an extension of time claim a Contractor must comply with the contract requirements:

  1. The Contractor must notify the Architect/Contract Administrator/Employer (depending on the contract) as soon as it realises the completion of the Works is or is likely to be delayed. The notice must include details of the material circumstances causing the delay to the progress of the Works and confirm the Relevant Event is excessively adverse heat conditions.[3]
  2. Additionally, for the Standard and D&B Contracts, the notice must be in writing stating details of the excessive heat, its expected effect on progress, and an estimate of the expected delays to completion after the Completion Date.[4]
  3. The Contractor should also continue to give notice of any changes in the estimated delay or other details and supply further requested information.[5]
  4. The guidance confirms a Contractor can support its claim by using a Downtime Report to show how the excessive temperatures experienced at the Site were greater than average when compared to weather data for the previous 10 years. Evidence could also include photos, site diaries, progress meeting minutes and other contemporaneous records.
  5. A decision on a claim for an extension to the Completion Date caused by the Relevant Event will be made within 12 weeks of receipt of the details from the Contractor.[6]

In summary, JCT contracts potentially permit a Contractor to claim an extension of time to the Completion Date due to excessive heat provided evidence proves the conditions are truly exceptional.

NEC3 and NEC4 engineering and construction contracts

Exceptionally adverse weather may be a Compensation Event entitling a Contractor to both an extension of time and financial relief under NEC3 and NEC4 contracts if specific criteria are met.[7] In contrast to the JCT, NEC contracts rely on empirical data to measure weather at a set location. The intention is to report weather on a calendar month basis rather than hourly or daily.

The contract lists the weather measurements recorded monthly as:

  • Cumulative rainfall (mm)
  • Number of days with rainfall more than 5mm
  • Number of days with minimum air temperatures less than 0 degrees Celsius
  • Number of days with snow lying.[8]

The standard form Contract Data Part One does not provide objective criteria for excessive heat conditions however space is included for adding in other measurements which could include excessive temperatures.

The relevant weather measurement must be:

  • Recorded within a calendar month (of the Compensation Event occurring)
  • Before the Completion Date for the whole of the Works
  • At the place stated in the Contract Data.[9]

The Contractor is entitled to a compensation event if the weather measurement is more adverse when compared with the weather data and is found to occur less frequently on average than once in 10 years. It is only the difference between the weather occurring and the average weather which is considered when determining a Compensation Event.

The Contractor must comply with the NEC procedural requirements when making a claim for a Compensation Event entitling it to an extension of time and money:

  1. The Contractor must notify the Project Manager of the Compensation Event relating to the exceptional weather within 8 weeks of becoming aware the event has happened[10] otherwise it loses its entitlement to any additional money or time due to this Compensation Event.
  2. If the Project Manager agrees there should be a change to the Completion Date, within one week of receipt of the Contractor's notification,[11] it will instruct the Contractor to provide quotations of the changes to the Prices and any delay to the Completion Date resulting from the exceptional weather.
  3. The quotation details must be supplied by the Contractor within three weeks of the Project Manager's instruction.[12]
  4. The Project Manager must reply within two weeks of the submission either accepting or requesting extra information.[13]

If a Contractor is uncertain about claiming relief specifically due to weather conditions, it could consider claiming using the catch-all compensation event provision that refers to an event that stops the Contractor completing the works and which neither Party could prevent and which would have been unreasonable to allow for given the small chance of it occurring.[14] Proving this might be difficult given the increasing occurrences of exceptional weather. This ground would usually cover exceptionally rare events e.g. a storm which does not occur more than once in ten years for the particular month.

On balance, a Contractor's Compensation Event delay claim, due to excessive heat, is unlikely to be successful under a NEC3 or NEC4 contract unless there is a specific amendment to permit this.

Practical tips for contractors before making an extension of time claim:

  1. Check the contract drafting to determine which party bears the risk for exceptionally adverse weather conditions.
  2. Follow the contractual requirements relating to the timing, content and form of applications.
  3. Keep updated records of the weather conditions on site to assist any claims and provide all evidence as requested in time.
  4. If a claim is rejected, consider referring the dispute to adjudication.

Duties of employers in excessive temperatures

Employers have a duty to ensure the health, safety and welfare at work of all Employees in so far as it is reasonably practical.[15] Morale and productivity are often adversely affected by rapid rises in heat gain. Therefore, it remains in an Employer's interests to adapt the working environment to ensure progress can be maintained despite excessive temperatures, reducing the risk of a Contractor attempting a claim.

Examples of hot weather adaptations employers can take to maintain progress include:

  1. Rescheduling works for times during the day with cooler temperatures.
  2. Permitting frequent breaks in shaded areas.
  3. Granting free access to cold drinking water.
  4. Adapting uniform and PPE requirements.
  5. Encouraging PPE removal during rest breaks to facilitate body heat loss.
  6. Informing the workforce about the physical symptoms of heat stroke.


Standard form construction contracts do not expressly deal with exceptionally hot weather but a claim is more likely to succeed under a JCT contract. Whether their drafting will modernise in their next iterations to expressly permit claims for excessive heat resulting in delays to the Completion Date remains to be seen. Predictions from the Met Office that climate change will make excessive temperatures more common also suggests excessively hot weather may not be exceptional for very long. For certainty, Contractors should negotiate to include excessive heat as a Compensation/Relevant Event in their contracts preferably specifying a temperature figure in the 30s rather than the 40s.

[1] JCT Standard without quantities 2016 Clauses 2.29.8; JCT Standard with quantities 2016 Clause 2.29.9; JCT Design & Build 2016 Clause 2.26.8; JCT Intermediate 2016 Clause 2.20.8

[2] As considered in Walter Lawrence v Commercial Union Properties (1984) 4 Con LR 37

[3] JCT Design & Build Contract 2016 Clause 2.24.1; JCT Standard 2016 Clauses 2.27; JCT Intermediate 2016 Clause 2.19

[4] JCT Design & Build Contract 2016 Clause 2.24.2

[5] JCT Design & Build Contract 2016 Clause 2.24.3; JCT Standard 2016 Clause 2.27.2

[6] JCT Design & Build Contract 2016 Clause 2.25.2; JCT Standard 2016 Clause 2.27.3

[7] NEC3 and NEC4 Engineering and Construction Contract Clause 60.1 (13)

[8] NEC3 and NEC4 Engineering and Construction Contract Data Part One, Clause 6

[9] NEC3 and NEC4 Engineering and Construction Contract Clause 60.1(13)

[10] NEC3 and NEC4 Engineering and Construction Contract Clause 61.3

[11]NEC3 and NEC4 Engineering and Construction Contract Clause 61.4

[12] NEC3 and NEC4 Engineering and Construction Contract Clause 62.3

[13] NEC3 and NEC4 Engineering and Construction Contract Clause 62.3

[14] NEC3 and NEC4 Engineering and Construction Contract Clause 60.1(19)

[15] Health and Safety at Work Act etc 1974, Section 2

This article is for general information only and reflects the position at the date of publication. It does not constitute legal advice.