Construction Claims and Disputes in an Era of Rising Temperatures

Introduction

The construction industry has long contended with weather as a source of delay, disruption, and defects. However, the nature and frequency of weather-related risks are fundamentally changing. Rising global temperatures, increasingly frequent heatwaves, and the broader consequences of climate change are transforming what was once a seasonal anomaly into a persistent and systemic project risk.[1] As the Climate Change Committee observed in its Fourth Independent Assessment of UK Climate Risk, published on 20 May 2026, “the UK was built for a climate that no longer exists.”[2]

This article examines the intersection of climate change, construction performance, and legal liability. It addresses three principal areas:

• First, the entitlement to extensions of time and the evidential challenges arising from heat-related delay events;
• Secondly, the impact of rising temperatures on defects, building performance, and professional liability; and
• Thirdly, emerging dispute trends as the legal and regulatory landscape adapts to a changing climate.

Delay and Disruption Claims: Extensions of Time for Extreme Heat

Extreme heat poses a dual threat to construction programmes. First, it directly impairs workforce productivity: a University of Reading study found that 67% of site workers expressed concern about the impact of heat on their health, 44% had experienced heat-related illness, and 87% reported increased fatigue in hot conditions.[3] As Dr Alba Fuertes of the School of Built Environment observed, “Heat is already a danger for workers on construction sites… yet there is no legally defined maximum workplace temperature to protect workers from excessive heat in the UK.”[4] Secondly, heat compromises material quality – for example concrete curing, where rapid evaporation in high temperatures is recognised as an enemy causing cracking and reduced strength.

Whether an extension of time (“EOT”) provision is triggered depends upon the proper construction of the relevant contractual clause. The principal standard forms adopt materially different approaches to this question.

Under JCT DB 2024, clause 2.26.10 entitles the contractor to an EOT for delay caused by “exceptionally adverse weather conditions.” The contract provides no definition of this phrase and prescribes no criteria. In the absence of a defining clause, the courts are likely to follow the approach set out in Lebeaupin v Richard Crispin and Co [1920] 2 K.B. 714, construing the words “with close attention to the words which precede or follow it, and with due regard to the nature and general terms of the contract,” having regard to the factual and commercial background. In Walter Lawrence v Commercial Union (1984) 4 Con LR 37, the court construed the JCT 1963 equivalent (“exceptionally inclement weather”) and held that the test is whether the weather itself was exceptional, not whether the resulting delay was exceptional.

FIDIC Red and Yellow Books 2017 (but not the Silver Book) address the issue at clause 8.5(c), which provides for an EOT where completion is delayed by “exceptionally adverse climatic conditions” at the site, which must be “Unforeseeable having regard to climatic data made available by the Employer… and/or climatic data published in the Country for the geographical location of the Site.” This formulation introduces an explicit foreseeability requirement tied to specific data sources, providing arguably greater contractual certainty than the JCT position.

NEC3 and NEC4 ECC clause 60.1(13) defines a compensation event by reference to adverse weather that, measured against local weather station data, occurs on average less frequently than once every ten years. Notably, the NEC (December 2025) recommended that users consider adapting standard weather provisions as extreme weather becomes more frequent and severe, observing that heat is not currently included in standard contract data.[5] The NEC suggested that parties should include measurements catering for extreme heat, adopt a pre-agreed baseline matrix of standard construction activities and weather variables, and consider hyperlocal or on-site weather station data to reduce disputes over causation.

A key risk allocation consideration arises from these differing formulations. As climate patterns shift, parties would be well advised to adopt more prescriptive definitions of adverse weather in bespoke amendments, rather than relying upon open-textured phrases whose meaning may be contested.

Establishing Entitlement: Evidencing Extreme or Exceptional Weather

The evidential burden of establishing an EOT entitlement for heat-related delay falls squarely upon the contractor. General bad weather will not usually suffice; the heat must represent a significant deviation from the average or historical norm for the time of year and place of works—that is, a temperature intensity outside the historical norm.

The question of what constitutes “unforeseeable” or “exceptionally adverse” weather is increasingly fraught. In a different context – a case concerning a package holiday – in the Court of Appeal’s judgment in Sherman v Reader Offers [2024] EWCA Civ 412, a tour operator invoked a force majeure clause requiring circumstances to be “unusual or unforeseeable” following disruption caused by unusual ice conditions. In Sherman v Reader Offers a travel company (Reader Offers) appealed against a decision that the respondents (Mr and Mrs Sherman) were entitled to compensation in respect of a package cruise. The Shermans had booked the 12-night ‘Northwest Passage’, however as a result of ice conditions, the cruise ship was able to visit very little of the Northwest Passage and instead the majority of the cruise was spent exploring the west coast of Greenland. The Shermans brought an action in the County Court in which they claimed their money back, together with compensation, on the basis that they ought to have been given notice of the changed arrangements and offered the right to cancel. The Court of Appeal held (at [99]) that although conditions were unusual for the time of year and beyond the operator’s control, they were not unforeseeable, given that “annual patterns that were once considered reliable are now very much less reliable… It was, therefore, entirely foreseeable that it might prove impossible to perform the cruise in accordance with the detailed itinerary.” At [100], the court observed: “Ironically, it was the very unforeseeability of ice conditions which was itself foreseeable.” This reasoning presents a cautionary precedent for parties seeking to characterise extreme heat events – or other weather patterns associated with climate change – as unforeseeable. This is particularly so in light of the Met Office’s 14 July 2026 report, ‘State of the UK Climate in 2025’,[6] the content of which was summarised by its lead author in this way: “What we used to think of as extreme, we increasingly consider as normal.”

In terms of evidencing whether a triggering event has happened, the parties will need to consider evidential sources. As to evidential sources contractors should, depending on the particular contract that applies to their project, consider: climatic data provided at the contracting stage (NEC4 “weather data”; FIDIC “climatic data”); Met Office data and reports; JCT’s collaboration with the Met Office producing location-based Weather Planning Reports and Downtime Reports (the latter indicating whether conditions exceed a one-in-ten-year value); reliable news sources; and contemporaneous site records including measurements, photographs, and site diaries. The contractor must gather evidence of the event, the date of knowledge, the effect on performance and the critical path (including, for example, the impact on concrete curing or the need for additional rest and hydration breaks), and the mitigation efforts undertaken.

The requirement to mitigate deserves particular attention. Force majeure clauses frequently impose reasonable or best endeavours obligations: JCT DB 2024 clause 2.25.6.1, for example, requires best endeavours to prevent delay. Even where the contract is silent on the point, a force majeure clause will be interpreted as containing a reasonable endeavour proviso. In RTI Ltd v MUR Shipping BV [2024] UKSC 18, the Supreme Court held that a reasonable endeavours obligation to overcome a force majeure event did not require acceptance of non-contractual performance from the counterparty absent clear words to the contrary. The court further observed that if the effects of a force majeure event could reasonably have been prevented, the cause of failure is properly attributed to the party’s inadequate response rather than to the event itself. This underscores the importance of careful drafting and contemporaneous record-keeping.

Defects, Performance Disputes, and Professional Liability in a Changing Climate

Beyond delay, rising temperatures raise fundamental questions about design responsibility, professional standards, and the long-term performance of the built environment. Construction professionals will increasingly be expected to deliver climate-resilient buildings and infrastructure capable of withstanding extreme weather, whilst simultaneously reducing operational and embodied carbon. Therefore, one can expect that climate change will place new stresses on existing professional duties.

An example of this is considering the judgment in MT Højgaard A/S v E.ON Climate and Renewables UK Robin Rigg East Ltd [2017] UKSC 59 in respect of design responsibility. The appeal in MT Højgaard arose from the foundation structures of two offshore wind farms at Robin Rigg, designed and installed by the respondent, MT Højgaard A/S. The offshore wind farms failed shortly after completion of the project and the dispute concerned who should bear the remedial costs in the sum of €26.25m. Amongst other things, the Technical Requirements called for the foundations to be in accordance with a document known as J101. J101 was a reference to an international standard for the design of offshore wind turbines published by an independent classification and certification agency. However, only later did a review show that J101 have an error in one of its formulas, so that formula was wrong by a factor of about ten. This error meant that the strength of the foundation structures had been substantially over-estimated. Clause 8.1(x) of the contract between the parties stated that MT Højgaard A/S should carry out the works so that they would be “fit for its purpose”. “Fit for Purpose” was ultimately defined in a way that it included adherence to the Technical Requirements. In respect of the contract there was a potential inconsistency between different parts of the contract, including that another provision required the foundations to be designed so that they would have a lifetime of twenty years.

Notwithstanding any potential inconsistency, the Supreme Court held unanimously that where two contractual provisions impose different or inconsistent standards, the more rigorous or demanding standard prevails, the less rigorous being treated as a minimum requirement. A party undertaking design responsibility may thus be held to a fitness-for-purpose or performance warranty standard – not merely reasonable skill and care – if the contract is drafted in outcome terms.

The relevance of MT Højgaard is that as tolerance requirements for heat and thermal performance of buildings become more exacting, this authority assumes heightened significance. Parties must be careful to ensure they understand any potential inconsistent requirements in their contract and bear in mind the more rigorous or demanding of the standards is likely to prevail.

A further issue for professionals is that as demands increase to guarantee the thermal performance and climate adaptation of buildings, professionals may have to adapt by employing novel techniques or materials. However, the standard of care is not lowered by inexperience. In IBA v BICC [1980] 5 WLUK 151, the designer of a television mast admitted no experience in cylindrical mast design and that the work was “both at and beyond the frontier of professional knowledge at the time.” In the House of Lords, Lord Edmund-Davies held at [10-24] that this “created a clear duty to identify and to think through such problems… so that dimensions of the ‘venture into the unknown’ could be adequately assessed” before deciding on practicability. Similarly, in Victoria University of Manchester v Hugh Wilson & Womersley [1984] 2 Con LR 43 Judge Newey gave some practical guidance to professionals when faced with these kinds of dilemmas. The court observed that using untried materials or techniques is not itself negligent, but professionals venturing into untried territory would be wise to warn clients specifically and obtain express approval. This reflects wider case law applying to professionals, for example Baylis Farms Ltd v RB Dymott Builders Ltd [2010] EWHC 3886 (QB), where a client was warned in clear terms of risk and instructed the contractor to proceed regardless, there was a consensual shifting of risk from contractor to employer.

The flip side is that professionals may try to defend their conduct by arguing that “everyone else was doing it”. Depending on the facts, this may be unlikely to offer refuge. For those acting in building safety cases there is an analogy to be made. In Martlet Homes Ltd v Mulalley & Co Ltd [2022] EWHC 1813 (TCC), at [271] HHJ Stephen Davies held that a defendant is not exonerated simply by proving that others were “just as negligent”; the Bolam principle does not operate as a “get out of jail free card.”

Finally, parties will need to consider design life obligations. An example of this is in Blackpool BC v Volkerfitzpatrick Ltd [2020] EWHC 1523 (TCC) which concerned a tram depot designed for a 50-year lifespan in an exposed coastal environment. HHJ Stephen Davies held (at [157]) that design life obligations have an “essentially strict character” as in MT Højgaard; a structure need not be maintenance-free for its whole design life but should not require major repairs over that period. Therefore, it would be prudent for designers to consider whether a building’s siting increases risk from storms and changing weather patterns.

An instructive illustration of such design modelling failures is provided by 20 Fenchurch Street, London (the Walkie Talkie). The building’s curved facade caused extreme downdrafts capable of knocking pedestrians over, whilst its concave glass front reflected and focused sunlight to create temperatures of up to 90°C at street level, requiring temporary screens and ultimately a permanent brise soleil at unplanned cost. The example illustrates the type of difficulties which will only become more challenging for designers and underscores the modelling expectations that will increasingly be placed upon designers as weather patterns become less predictable.

Future Dispute Trends: Foreseeability, Resilience, and Adaptation

Climate change is reshaping the risk landscape of major construction projects. It is often said that climate change is not a creator of disputes but a multiplier of disputes – it exacerbates existing contractual tensions and amplifies the consequences of inadequate risk allocation. Moving forwards judges, arbitrators, and adjudicators will need to reconsider what ‘unforeseeable’ means as climate extremes become the new normal.

Parties will also need to consider the transition risk that will become increasingly prevalent – that is, risk arising from regulatory or policy change. Restrictions on greenhouse gas emissions, bans on certain building materials, and climate-related planning or zoning changes may prevent contract performance in circumstances falling within a force majeure clause that provides for government action. The Building Safety Act 2022 demonstrates that where public policy requires it, government will change the law and reallocate responsibility for buildings, even retrospectively. Climate adaptation may see similar regulatory intervention.

The Climate Change Committee’s Fourth Independent Assessment[7] warns that increasingly extreme and frequent heatwaves represent the greatest health risk from climate change in the United Kingdom; annual heat-related excess deaths currently range from 1,400 to 3,000 per year, potentially rising to 3,000-10,000 per year by 2050 under 2°C of global warming without additional adaptation. The report concludes that new buildings should be designed to keep people cool via both active and passive cooling measures from the outset. This imperative will generate disputes centred on energy modelling, performance specifications, and what it truly means to “futureproof” a structure.

Future design responsibility disputes will turn on whether a building’s failure to meet passive cooling standards during a heatwave, or its inability to manage flooding, constitutes a professional negligence design flaw or a missed climate adaptation issue. The distinction may prove elusive, but the consequences for professionals and their insurers will be significant.

Conclusion

The foregoing analysis demonstrates that rising temperatures are no longer an exceptional or transient risk for the construction industry. They are a structural feature of the operating environment, with implications that permeate every stage of a project’s lifecycle – from procurement and risk allocation, through construction performance and delay management, to long-term building performance and professional accountability.

Standard form contracts, drafted for a climate that no longer exists, are proving inadequate. The JCT’s open-textured “exceptionally adverse weather conditions,” FIDIC’s foreseeability requirement, and the NEC’s ten-year statistical threshold all face challenges of interpretation and application as the frequency and severity of extreme heat events accelerate. Existing case law – from Sherman v Reader Offers on foreseeability, to MT Højgaard and Blackpool BC v Volkerfitzpatrick on design obligations – signals that the courts will hold parties to exacting standards, and that reliance upon historical norms provides diminishing protection.

Looking forward, the construction industry must proactively embed climate risk allocation into its contracts, design standards, and procurement strategies. This requires more prescriptive contractual definitions of adverse weather events; pre-agreed baselines and measurement methodologies; robust contemporaneous record-keeping; express allocation of transition and supply chain risk; and a design philosophy that accounts not merely for historical climate data but for credible future projections. Those who fail to adapt their contractual and professional practices to the reality of a changing climate will find themselves increasingly exposed – both to the physical consequences of rising temperatures and to the legal consequences of inadequate preparation.

[1] See, Met Office ‘Climate extremes are becoming the new ‘normal’ for the UK’, 14 July 2026: https://www.metoffice.gov.uk/about-us/news-and-media/media-centre/weather-and-climate-news/2026/climate-extremes-are-becoming-the-new-normal-for-the-uk.

[2] Available at: https://www.theccc.org.uk/publication/a-well-adapted-uk/.

[3] See, University of Reading, ‘Construction sites are not ready for extreme heat’ dated 25 June 2026: https://www.reading.ac.uk/news/2026/Research-News/Construction-sites-are-not-ready-for-extreme-heat.

[4] Ibid.

[5] See, ‘Weather risk under NEC4 contracts: suggestions for a fairer approach’, 9 December 2025. Available at: https://www.neccontract.com/news/weather-risk-under-nec4-contracts-suggestions-for-a-fairer-approach?srsltid=AfmBOorLdP4d3ds8xjfz_5h2BfBQidHI3A77XoqzjtKzu7EmbYA1GAaM.

[6] The Met Office Hadley Centre Climate Programme, ‘State of the UK Climate in 2025’, 14 July 2026. Available at: https://rmets.onlinelibrary.wiley.com/doi/10.1002/joc.70470.

[7] Available at: https://www.theccc.org.uk/wp-content/uploads/2026/05/A-Well-Adapted-UK-CCRA4-IA-784y9813-3094039i85t59yhfufoub24f2bipdj1.pdf.