The incoming heat wave this weekend will see temperatures hit 29°C in some parts of the country, and the Federation of Master Builders (FMB) is revealing what effect this has on construction
The latest State of Trade survey from the FMB and CIOB shows that heat wave project delays are affecting many firms, as 40% cite extreme weather or climate events as a cause of delays in H2 2025.
This makes it the biggest factor in causing delays, as the second biggest factor is planning delays at 36%, and market uncertainty is third at 35%.
Delays are far more common than not
Nine in ten firms experienced a delay in the second half of 2025, up from eight in ten in the previous survey.
Extreme heat significantly slows work, as mandatory rest breaks and the need to reschedule outdoor tasks in the heat can bring work to a crawl. Employers must ensure workers have access to shade, hydration, and sun cream with an SPF of at least 30.
It will likely be necessary to remind clients that adaptation will be needed in hot weather conditions, and that delays are likely.
Brian Berry, chief executive of the FMB, said: “The summer months are when our members are at their busiest but working outdoors in high temperatures carries real risks. Heat exhaustion and sunburn can put skilled tradespeople out of action and put projects back further.
“We’ll be watching the weather data closely in our next survey, but the direction of travel is clear – extreme weather is becoming an increasingly serious operational challenge for small builders across the UK. Our message to firms is simple: protect your workforce and our message to clients is: a firm that looks after its workers is exactly the kind of firm you want on your job.”
Workers should be aware of their rights when working during a heatwave
Writing for PBC Today, legal and compliance director at National Accident Helpline, Jonathan White, discussed how there is no law that specifies a temperature that is considered too hot to work, but that employees have rights that employers must meet.
Jonathan wrote: “Recent reports show that England is not ready to respond to extreme heatwaves this summer, with researchers warning of economic shocks and a breakdown in public services should the country experience more very high temperatures either this year or in the future.
“Elsewhere we’re seeing more countries taking precautionary measures to protect workers against the changing climate, with Spain banning outdoor working during heatwaves a few weeks ago.
“As the UK summer heat is ramping up, with reports of mini-heatwaves and Storm Oscar bringing in temperatures of 30 degrees Celsius in some parts of the nation, it’s time for the UK to look at how it can protect its workers from heat stroke and other heat-related illnesses or injuries.”
Read Jonathan’s thoughts and what employers must provide during a heatwave here.
The FMB have also published their own sun safety guidance which is available here.
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