Construction remains one of the highest-risk industries in the UK, and most site teams will already know that a small number of hazards are responsible for a large proportion of serious injuries and fatalities. When people ask “what are the big 4 in construction?”, they are referring to the four leading causes of fatal and major accidents on site: falls, struck-by incidents, electrocutions, and caught-in or between accidents.
Understanding these risks is not just a box-ticking exercise. It is central to better planning, safer delivery, and stronger compliance. It also links directly to another question many contractors ask: what biggest problem construction sites face today? For many firms, the biggest problem is not simply one individual hazard, but the challenge of consistently identifying, communicating, and controlling risks before work starts.
With better pre-construction planning, site coordination, and digital record-keeping, contractors can reduce exposure to these common dangers. That is where platforms such as SiteSamurai can make a practical difference.
What are the big 4 in construction?
The big 4 construction hazards are:
<ol class="my-4 space-y-2"><li class="ml-4 list-decimal list-inside">
Falls from height </li><li class="ml-4 list-decimal list-inside">
Struck by moving or falling objects </li><li class="ml-4 list-decimal list-inside">
Electrocutions </li><li class="ml-4 list-decimal list-inside">
Caught in or between objects, equipment, or materials</li></ol>
These four categories are widely recognised because they repeatedly appear in serious incident statistics across construction projects of all sizes, from housebuilding and fit-out work to civil engineering and commercial developments.
Although terminology can vary slightly between regions and reporting bodies, the underlying message is the same: if you control these four risks effectively, you will significantly reduce the chance of severe accidents on site.
1. Falls from height
Falls are consistently one of the most serious risks in construction. In the UK, work at height remains a major cause of fatal and life-changing injuries. This includes falls from:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">Scaffolding</li><li class="ml-4 list-disc list-inside">Ladders</li><li class="ml-4 list-disc list-inside">Roof edges</li><li class="ml-4 list-disc list-inside">Open stairwells</li><li class="ml-4 list-disc list-inside">MEWPs</li><li class="ml-4 list-disc list-inside">Fragile surfaces</li><li class="ml-4 list-disc list-inside">Partially completed structures</li></ul>
A typical example might be a roofing subcontractor carrying out edge work on a warehouse extension. If the work area has not been properly sequenced, edge protection is incomplete, and access arrangements are unclear, the risk of a fall rises sharply.
Common causes include poor access planning, missing guardrails, inadequate supervision, rushed programmes, and failure to inspect temporary works.
How to reduce the risk of falls
Practical controls include:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">Planning work at height properly before mobilisation</li><li class="ml-4 list-disc list-inside">Using the right access equipment for the task</li><li class="ml-4 list-disc list-inside">Ensuring scaffolds and platforms are inspected and signed off</li><li class="ml-4 list-disc list-inside">Installing edge protection and covers over openings</li><li class="ml-4 list-disc list-inside">Briefing operatives through daily site inductions and task-specific RAMS</li><li class="ml-4 list-disc list-inside">Monitoring changes in site conditions as the job progresses</li></ul>
Using SiteSamurai, site managers can keep RAMS, inspection records, snagging items, and safety actions in one place. That means if a missing handrail, exposed edge, or incomplete scaffold is identified during a walkround, it can be logged, assigned, and tracked quickly rather than being buried in emails or paper notes.
2. Struck-by incidents
The second of the big 4 in construction involves workers being struck by something. This could be a moving vehicle, swinging load, collapsing material stack, or falling tool.
Examples include:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">A banksman standing too close to a reversing dumper</li><li class="ml-4 list-disc list-inside">A labourer hit by materials dropped from a scaffold lift</li><li class="ml-4 list-disc list-inside">A pedestrian struck by an excavator slewing in a tight work zone</li><li class="ml-4 list-disc list-inside">A worker injured by unsecured plasterboard sheets tipping over</li></ul>
Struck-by incidents are especially common on busy sites where multiple trades are working in the same area and logistics are not tightly controlled.
How to reduce struck-by risks
Key measures include:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">Clear traffic management plans</li><li class="ml-4 list-disc list-inside">Segregated pedestrian and plant routes</li><li class="ml-4 list-disc list-inside">Proper lifting plans and exclusion zones</li><li class="ml-4 list-disc list-inside">Good housekeeping and safe material storage</li><li class="ml-4 list-disc list-inside">Secure tool tethering where required</li><li class="ml-4 list-disc list-inside">Strong supervision during deliveries and crane operations</li></ul>
This is one area where digital coordination really helps. With SiteSamurai, teams can raise issues during site inspections, attach photos, mark exact locations, and make sure corrective actions are visible to everyone involved. If a delivery zone is too congested or an exclusion barrier is missing, the issue can be escalated immediately instead of waiting for the next coordination meeting.
3. Electrocutions
Electrical hazards remain one of the most dangerous issues on construction projects. Electrocution can result from direct contact with live cables, damaged temporary power supplies, poorly managed isolation procedures, or contact between plant and overhead lines.
A common scenario on a groundworks package is an excavator striking buried services because the permit-to-dig process was weak and service drawings were outdated. On fit-out projects, another frequent issue is operatives working with damaged leads, overloaded temporary boards, or untested equipment.
How to reduce electrical hazards
Good practice includes:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">Verifying utility surveys and service locations before excavation</li><li class="ml-4 list-disc list-inside">Using permit-to-work systems for high-risk activities</li><li class="ml-4 list-disc list-inside">Inspecting temporary electrics regularly</li><li class="ml-4 list-disc list-inside">Keeping cables protected and routes organised</li><li class="ml-4 list-disc list-inside">Ensuring lock-off and isolation procedures are followed</li><li class="ml-4 list-disc list-inside">Training workers to recognise electrical danger zones</li></ul>
One of the biggest problems construction sites face is fragmented information. A service drawing in one folder, a permit in another, and a site instruction in someone’s inbox is a recipe for mistakes. SiteSamurai helps reduce that risk by keeping essential documents, actions, and site observations organised and accessible, so teams are not relying on memory or outdated paperwork.
4. Caught-in or between accidents
The fourth of the big 4 construction hazards covers incidents where someone is caught in, under, or between machinery, structures, materials, or equipment. These accidents are often severe because they involve crushing, entrapment, or collapse.
Examples include:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">A worker trapped between plant and a wall in a narrow access route</li><li class="ml-4 list-disc list-inside">An operative caught in moving mechanical parts</li><li class="ml-4 list-disc list-inside">A trench collapse trapping groundworkers</li><li class="ml-4 list-disc list-inside">A subcontractor crushed while adjusting materials in a loading area</li></ul>
These incidents often happen when workfaces are congested, sequencing has broken down, or temporary support arrangements are inadequate.
How to reduce caught-in/between risks
Contractors should focus on:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">Safe excavation design and trench support</li><li class="ml-4 list-disc list-inside">Plant exclusion zones</li><li class="ml-4 list-disc list-inside">Lockout procedures for machinery maintenance</li><li class="ml-4 list-disc list-inside">Proper sequencing of deliveries and lifting operations</li><li class="ml-4 list-disc list-inside">Temporary works checks and sign-offs</li><li class="ml-4 list-disc list-inside">Better communication between supervisors and trades</li></ul>
For example, on a city-centre basement project, access routes can change daily as excavation progresses. If route updates, temporary works status, and plant movements are not communicated clearly, operatives can easily end up in unsafe areas. SiteSamurai supports this by giving teams a simple way to record changing site conditions, assign actions, and maintain a visible audit trail.
What biggest problem construction sites face?
If you look beyond the hazards themselves, the biggest problem in construction is often poor coordination of risk information. Most accidents do not happen because nobody knew the hazard existed. They happen because:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">Risks were identified but not acted on</li><li class="ml-4 list-disc list-inside">Controls were not communicated properly</li><li class="ml-4 list-disc list-inside">Site conditions changed and documents were not updated</li><li class="ml-4 list-disc list-inside">Too many systems relied on paper, memory, or disconnected spreadsheets</li><li class="ml-4 list-disc list-inside">Supervisors and subcontractors did not have one clear version of the truth</li></ul>
In other words, the problem is rarely just falls, electrocutions, or moving plant in isolation. It is the failure to manage them consistently across the life of the project.
That is why better digital site management matters. SiteSamurai helps contractors bring inspections, snagging, actions, photographic evidence, and safety observations together in one platform. Instead of chasing updates across WhatsApp messages, clipboards, and email chains, project teams can deal with issues in real time.
Why the big 4 still matter on modern sites
Even with better regulations, training, and equipment, the big 4 in construction remain relevant because modern sites are fast-moving and complex. Programmes are tight, labour is stretched, and multiple subcontractors often work side by side in changing conditions.
Whether you are running a residential scheme, a school extension, or a major civils package, the fundamentals stay the same:
<ul class="my-4 space-y-2"><li class="ml-4 list-disc list-inside">Plan high-risk work properly</li><li class="ml-4 list-disc list-inside">Communicate controls clearly</li><li class="ml-4 list-disc list-inside">Inspect regularly</li><li class="ml-4 list-disc list-inside">Close out issues quickly</li><li class="ml-4 list-disc list-inside">Keep accurate records</li></ul>
This is where SiteSamurai adds practical value. It supports site managers and project teams who need to spot hazards early, log issues clearly, and make sure actions are not forgotten.
Final thoughts
So, what are the big 4 in construction? They are falls, struck-by incidents, electrocutions, and caught-in or between accidents. These are the hazards most likely to cause serious harm, and they should be central to every contractor’s planning and supervision process.
If you are also asking what biggest problem construction faces, the answer is often poor risk coordination rather than a single isolated danger. The firms that perform best are the ones that combine strong site leadership with clear, live information.
By using a platform like SiteSamurai, construction teams can improve visibility, accountability, and response times across the project. And when safety actions are easier to record, assign, and close out, the chances of preventing the next serious incident improve dramatically.