Lone Working on Construction Sites: Risk Assessment Guide

Lone working on construction sites carries risks that are easy to underestimate. When something goes wrong and nobody is nearby, the consequences of even a minor incident can escalate rapidly. This guide covers the legal requirements, practical risk assessment process, essential control measures, and emergency procedures that UK construction site managers need to implement for anyone working alone.

What Counts as Lone Working

A lone worker is anyone who works by themselves without close or direct supervision. On construction sites, this is more common than many people realise. Examples include security guards on overnight site watch, surveyors carrying out pre-construction surveys, maintenance workers carrying out repairs on occupied buildings, electricians and plumbers working in individual rooms or floors, site managers carrying out weekend checks, small contractors working on domestic refurbishments, and workers carrying out inspections in confined spaces, at height, or in remote areas of a large site.

The Health and Safety at Work Act 1974 and the Management of Health and Safety at Work Regulations 1999 do not prohibit lone working. However, they require employers to assess the risks of lone working and put adequate control measures in place. In construction specifically, the CDM 2015 Regulations require the principal contractor to plan, manage, and monitor the construction phase in a way that ensures health and safety. This includes managing the risks associated with anyone working alone on the site.

Why Lone Working Is Higher Risk

Working alone does not inherently create new hazards, but it significantly increases the consequences of existing hazards. The key factors that make lone working more dangerous include delayed emergency response, where if a lone worker suffers an injury, collapse, or medical emergency, there is nobody to call for help immediately. A fall from a ladder that results in a broken leg is serious but survivable when colleagues are nearby. The same fall when working alone in a remote part of a site, with no mobile phone signal, can be fatal if the worker cannot reach help.

There is also increased vulnerability to violence, particularly relevant for security staff, surveyors working in isolated locations, and workers on occupied premises. Without colleagues nearby, a lone worker is more vulnerable to assault, intimidation, or robbery.

Additionally, lone workers lack the benefit of having a colleague who can spot errors, warn of hazards, or provide a second opinion on decisions. A worker operating alone makes all judgments independently, without the safety net of a colleague who might notice that the scaffold is incomplete, the excavation is unsupported, or the weather conditions have deteriorated.

Conducting the Risk Assessment

A lone working risk assessment should be carried out for every situation where someone will work alone on a construction project. The assessment follows the standard five-step process but with specific attention to the unique risks of isolation.

Step 1: Identify the hazards specific to lone working

Consider every task the lone worker will carry out and identify which hazards are made worse by the absence of others. Key questions include can the work area and access routes be made safe by one person alone? Is there a risk of violence or intrusion from members of the public? Does the work involve lifting, handling, or moving heavy objects that normally require two people? Does the work involve any activities that regulations specify require more than one person (such as confined space entry)? Does the worker have any medical conditions that could lead to sudden incapacitation? Is the work location remote, difficult to access, or lacking mobile phone signal?

Step 2: Identify who might be harmed

The lone worker themselves is the primary person at risk, but consider also whether their work could create risks for others. A lone worker using power tools in an occupied building could create risks for building occupants. A lone security guard who suffers a medical emergency leaves the site unsecured.

Step 3: Evaluate the risks and decide on controls

For each identified hazard, determine whether the work can safely be carried out by a lone worker with appropriate control measures, or whether the risk is too high and the work must not be done alone. The hierarchy of controls for lone working is to avoid lone working where reasonably practicable by scheduling work to coincide with others on site. Where lone working cannot be avoided, implement control measures such as check-in systems, personal alarms, and activity restrictions. Finally, provide emergency procedures specific to the lone working situation.

Step 4: Record the assessment

The assessment must be recorded if there are five or more employees, but best practice is to record all lone working assessments regardless of company size. The record should identify the specific lone working situation, the hazards identified, the control measures in place, and any restrictions on what the lone worker can and cannot do. Site Manager AI can generate comprehensive lone working risk assessments that cover all the required elements and comply with UK regulations.

Step 5: Review and update

Lone working risk assessments should be reviewed whenever the work changes, the location changes, the person changes (different workers may have different medical conditions or experience levels), or following any incident or near miss.

Essential Control Measures

Communication and check-in systems

The single most important control measure for lone workers is a reliable system to maintain contact and raise the alarm if something goes wrong. Options include regular scheduled check-ins where the lone worker contacts a designated person at agreed intervals (for example, every two hours). If a check-in is missed, the designated person follows an escalation procedure. Lone worker devices and apps provide GPS tracking, automatic fall detection, and panic buttons that alert a monitoring centre. These are particularly valuable for workers in remote locations. Mobile phones with confirmed signal coverage are the minimum requirement. If there is no mobile signal at the work location, alternative communication must be provided (two-way radio, satellite phone, or a landline).

Activity restrictions

Certain activities should be prohibited for lone workers because the risk cannot be adequately controlled without another person present. These include working at height above two metres (except on a purpose-designed mobile tower scaffold with outriggers), entry into confined spaces (the Confined Spaces Regulations 1997 effectively require a standby person), hot work (welding, cutting, or burning) where fire watch is required, working with or near live electrical installations, operating heavy plant or machinery where a banksman would normally be required, and work involving hazardous substances where emergency decontamination may be needed.

Medical fitness

Lone workers must be medically fit for the work they will carry out alone. Any medical condition that could lead to sudden incapacitation, such as epilepsy, diabetes requiring insulin, severe asthma, or certain heart conditions, must be assessed. This does not necessarily mean that workers with these conditions cannot work alone, but the risk assessment must consider them and implement additional controls where needed.

Training and competence

Lone workers must be competent to carry out their work without direct supervision. This means they need adequate training and experience for the specific tasks they will perform, knowledge of the risks and control measures identified in the risk assessment, ability to recognise situations that are beyond their competence and to stop work, and first aid training (at minimum, emergency first aid at work).

Emergency Procedures for Lone Workers

Generic site emergency procedures are usually designed for situations where multiple people are present. Lone workers need specific emergency procedures that address how to raise the alarm when alone and potentially incapacitated, who will respond and how quickly they can reach the lone worker's location, how the lone worker's location will be identified (particularly on large or complex sites), and what first aid provision is available.

The emergency procedure should be documented, communicated to the lone worker before they start work, and tested periodically. A check-in system is only effective if the escalation procedure has been rehearsed and all parties understand their roles.

Legal Requirements and Enforcement

The HSE takes lone working seriously. HSE inspectors visiting construction sites will ask whether lone working has been identified and risk assessed, whether appropriate control measures are in place, whether communication systems are working and tested, whether workers have been trained in lone working procedures, and whether the risk assessment is reviewed regularly.

Enforcement action for failures in lone working management can range from improvement notices to prosecution. Where a lone worker is injured or killed, and the investigation reveals inadequate risk assessment or control measures, the consequences for the employer can include unlimited fines and, where gross negligence is proven, imprisonment for individual managers under the Corporate Manslaughter and Corporate Homicide Act 2007.

Maintaining thorough documentation of lone working arrangements is essential. Digital tools that automatically log check-ins, record GPS positions, and store risk assessments provide strong evidence of compliance. Paper-based systems are less reliable and harder to retrieve during an investigation.

Practical Tips for Site Managers

Based on practical site experience, here are the measures that make the biggest difference to lone worker safety.

Brief every lone worker before they start. Even experienced workers need a site-specific briefing covering the layout, hazards, communication arrangements, and emergency procedures for the specific location.

Test communication before work starts. Confirm that the phone works, the check-in system is functioning, and the designated contact person is available. Do not assume that mobile signal exists everywhere on site.

Limit the duration. Where possible, limit lone working periods. A worker who will be alone for two hours faces significantly less risk than one who will be alone for an entire shift.

Provide a means of raising the alarm. This should not depend solely on the worker's own phone. Consider personal alarms, lone worker devices with automatic fall detection, or a landline at the work location.

Consider the time of day. Lone working outside normal hours (early mornings, evenings, weekends) carries additional risks including reduced visibility, lower temperatures, and delayed emergency service response times. Increase control measures accordingly.

Document everything. Record the risk assessment, the check-in schedule, the actual check-ins, and any incidents or near misses. Use digital site diary tools to create a real-time record that demonstrates compliance.