How to prevent fire spreading on construction sites

Posted 6 years ago

Construction sites are inherently high-risk environments for fires, with numerous potential ignition sources and combustible materials often present. In 2022/23, there were 309 fires reported in buildings undergoing renovations across the UK, marking an increase from the previous year. While some fires are accidental and others deliberate, many could have been prevented, or at least controlled more effectively, with the right precautions in place.

So, how can you reduce the risk and stop fires from spreading if one breaks out? Here’s what you need to know.

What are the common fire risks on construction sites?

Construction sites are full of potential fire hazards, many of which are often overlooked during day-to-day operations. Understanding these risks is the first step in preventing fires and minimising damage if one occurs. Here are some of the most common causes of fires on construction sites:

Electrical faults – Temporary wiring, overloaded circuits, and damaged or exposed cables can significantly increase the risk of electrical fires. Qualified professionals should carry out all electrical installations, and equipment should undergo regular PAT testing. Damaged tools or cables must be removed from use immediately.
Flammable Materials – Timber, insulation, fuel, solvents, paints, and packaging are just a few of the combustible materials typically found on site. Poorly stored materials, especially when placed near ignition sources or in confined, unventilated areas, can quickly fuel a fire.
Hot work – Welding, cutting, grinding, and soldering generate sparks and intense heat, making them one of the leading causes of fire on site. In fact, around 20% of fires reported on construction sites in 2023/24, were from hot work such as welding or cutting. A strict permit-to-work system, fire-resistant barriers, and fire watch protocols are essential to managing this risk.
Lack of fire safety maintenance – Fire extinguishers, alarms, and other safety systems must be regularly inspected and maintained to remain effective. Blocked fire escape routes or broken signage can also pose serious risks during an emergency.
Arson – While around 60% of construction fires are accidental, around 40% are attributed to deliberate malicious acts (arson). The open and often poorly secured nature of many construction sites can make them an easy target. Security measures like fencing, lighting, CCTV, and on-site security can significantly reduce this risk.

Choosing an appropriate fire extinguisher

It’s crucial that you have the correct fire safety products on site, and fire extinguishers are the weapon of choice for smiting small fires on a construction site.

Types of extinguishers and their uses

Different materials burn differently, so it’s important to match the extinguisher to the type of fire:

Water extinguishers – Best for Class A fires involving solid combustible materials like wood, paper, and textiles. These are common on construction sites, especially in timber structures or waste piles.
Avoid using it on electrical fires or flammable liquids as it can spread the fire or cause an electric shock.
Foam extinguishers – Suitable for Class A and B fires, including flammable liquids like petrol, diesel, and paint. Foam creates a barrier that cools the fire and smothers vapours to prevent reignition.
Foam extinguishers are not suitable for electrical fires.
Dry Powder extinguishers – Versatile and effective on Class A, B, and C fires, including gas fires and live electrical equipment. This makes them useful in high-risk zones with mixed materials.
However, they can reduce visibility and leave residue, so they’re best used outdoors or in well-ventilated areas.
CO₂ extinguishers – Ideal for electrical fires, such as those involving power tools, distribution boards, or temporary wiring. They work by displacing oxygen and leave no residue.
Keep in mind that they offer little cooling effect, so reignition is possible once the CO₂ disperses.

These extinguishers should be positioned at clearly marked fire points across the site, especially near high-risk areas such as hot works zones, fuel storage, or plant machinery.

How many fire extinguishers are needed on a construction site?

There’s no one-size-fits-all answer as it depends on the size, layout, and level of risk on site. However, a good rule of thumb from British Standards (BS 5306) is:

At least two Class A (e.g. water or foam) extinguishers per floor of a building under construction.
Fire points should be no more than 30 metres apart, so extinguishers are always within easy reach.
Additional extinguishers should be placed in areas with specific risks, like electrical equipment or flammable liquids.

A fire risk assessment will determine the exact number and placement of extinguishers needed for your site.

How to prevent fires from spreading in future

While the ultimate aim is to prevent fires altogether, it’s just as important to have measures in place to stop a fire from spreading if one does occur. Fast-moving fires can endanger lives, destroy materials, and cause significant delays to your project. The steps below can help you contain a fire early and minimise the damage.

Carry out a risk assessment

It’s a legal obligation under the FSO 2005 that a “responsible person” must carry out a risk assessment on a construction site (or any work premises, as a matter of fact).

There are certain elements you must assess when it comes to a fire risk assessment. The HSE states that these are the five steps in carrying out a fire risk assessment:

Identify hazards – consider how a fire could start and what could burn;
Identify those at risk – employees, contractors, visitors, and anyone who is vulnerable;
Evaluation and action – consider the hazards and people identified in 1 and 2 and act to remove and reduce risk to protect people and premises;
Record, plan, and train – keep a record of the risks and action taken. Make a clear plan for fire safety and ensure that people understand what they need to do in the event of a fire; and
Review – your assessment should be regularly reviewed to make sure that it takes account of any changes on site

Provide the appropriate training

Fire Awareness Training is a legal requirement for every workplace and, under both the CDM Regulations & the HASAWA 1974, employers are obliged to ensure this training is undertaken by every member of staff.

As well as showing due diligence to the pieces of legislation, Fire Awareness Training provides all workers with the knowledge to identify fire hazards and to reduce risks in the workplace.

Ultimately, a well-trained team means fewer accidents, less disruption, and a stronger safety culture, which is not only good for morale but can also reduce insurance premiums and protect your bottom line.

Use fire compartmentation to slow the spread

Temporary fire-resistant barriers, sheeting, or other forms of fire compartmentation can divide the site into zones, helping to contain any fire to a single area.

This simple strategy can protect high-risk areas, such as fuel storage or welding zones, and drastically reduce the speed at which a fire moves through a site.

By slowing the spread, you gain valuable time for evacuation and fire service response, potentially saving equipment, materials, and even structural elements of the build.

This could mean the difference between a minor delay and a full site shutdown, helping you avoid spiralling costs and project overruns.

Control hot works with a permit system

Hot works like welding, soldering, and grinding are a leading cause of construction site fires. Putting a strict permit-to-work system in place ensures proper planning and supervision before these tasks go ahead.

Including fire watches after hot works is essential to detect lingering sparks or heat that could otherwise go unnoticed.

Taking this seriously not only reduces fire risk but also shows your commitment to best practice, something that can strengthen client trust and support regulatory compliance during inspections.

Install temporary fire detection and alarm systems

Temporary or portable fire alarm systems offer early warning, especially on larger or multi-storey sites where visual detection may be difficult. These systems are quick to install and can be repositioned as the build progresses.

Early detection means quicker evacuation and a faster response from emergency services, reducing the chance of major losses.

It’s a cost-effective way to meet fire safety obligations while protecting the people, materials, and progress of your project.

Putting these measures in place doesn’t just help you tick compliance boxes—it protects your people, your schedule, and your reputation. Now that you’ve got prevention and containment covered, let’s take a look at another key piece of the puzzle: choosing the right fire extinguishers for your site and making sure they’re placed where they’ll be most effective.

Get up to date with your fire safety training in construction with iHasco

Feeling like it’s time to refresh your team’s fire safety knowledge? If you want to bring your workforce up to speed with the latest fire safety guidance, our online construction training makes it easy.

At iHasco, we offer CPD-accredited, IOSH-approved Fire Awareness Training for Construction that’s designed specifically for the industry. The course is accessible online, easy to complete, and built to help workers stay safe on-site.

Our training will help your team:

Identify common fire hazards found on construction sites
Understand exactly what actions to take if a fire breaks out
Meet the legal requirements of The Fire Safety Order 2005 and CDM Regulations 2015
Recognise different types of fire safety signs and what they mean

…and much more.

Whether you’re a site manager looking to stay compliant or a business owner committed to keeping your people safe, our training is a smart, hassle-free solution.

Try our free demo today and see just how easy it is to strengthen fire safety on your construction site.