> Disclaimer: SiteKiln gives you plain-English information, not legal or health and safety advice. Always follow your site-specific risk assessments and talk to a qualified professional.
The short version
The law says you must prevent danger to anyone in or near an excavation -- that means planning, locating and isolating services, and supporting or battering sides so they can't collapse without warning.
Under CDM, the contractor or principal contractor running the job is on the hook for planning, managing and monitoring excavation work; HSE's HSG185 and related guidance then set the detail on shoring, sloping, inspections and service detection.
Your duties in law (in plain English)
Several bits of law bite on excavations:
- CDM 2015: principal contractors and contractors must plan, manage and monitor excavation work so it's carried out without risks, including stability and services.
- Health and Safety at Work etc. Act: general duty to ensure, so far as reasonably practicable, the health and safety of workers and others.
- Specific excavation guidance: HSE's excavation page sums it up: "The law says you must prevent danger to workers in or near excavations. A competent person must inspect excavations at specified times."
So if you're running the dig -- as main contractor, groundworker, or small builder -- the legal responsibility sits with you to get this right.
Collapse -- what you must do to prevent it
HSE's excavation guidance and "Safety in excavations" good practice boil down to this:
Treat all excavations as capable of collapse unless you've got clear evidence otherwise -- even "good ground" can go without warning.
Where there's a risk of collapse, you must support the sides or batter/bench them back to a safe angle, and keep spoil and loads away from the edge.
In practice that means:
- Use suitable shoring systems -- timbering, trench boxes, sheets and frames, proprietary supports -- designed and installed by competent people, especially for deeper or longer-lasting digs.
- If you can't shore (rare in urban work), you must batter back the sides to a safe angle and keep plant, spoil and materials well back -- often impractical in tight sites.
- Never let people work in an unsupported vertical-sided trench where they could be buried, even if it "looks firm" or is "only" a couple of metres deep -- HSE enforcement and fatal cases show why.
HSE-backed guidance makes it clear: even shallow trenches can be deadly if people are kneeling or bending in them -- it's not just very deep digs that need support.
Services -- what you must do before and during digging
Hitting an underground service can kill people and cause major damage. HSE and related guidance (often referred to alongside HSG47) expect you to:
- Get service information before you dig: utility plans, as-builts, client information, surveys -- and treat them as guides, not exact maps.
- Scan and mark services on site using cable locators, GPR or other methods, and mark up the ground.
- Use safe digging techniques: trial holes, hand digging around expected services zones, digging in stages and never going at services blindly with a machine.
- Control plant: have clear, competent supervision when machines dig near services; use agreed stand-off distances and methods.
Hitting gas, HV electric or major water/sewer lines is not "just one of those things" -- HSE treat it as a planning and control failure.
Inspections and competent persons
HSE say excavations must be inspected by a competent person:
- At the start of every shift when people will work in them.
- After any event likely to affect stability or safety -- heavy rain, freezing/thawing, plant striking the sides, changes to supports.
- At other suitable intervals depending on risk and how the excavation is changing.
Inspections should be recorded, and if a danger is identified, no one should enter until it's remedied.
"Competent" here means someone with enough knowledge, experience and training to know what to look for -- not just whoever's free that morning.
What this means for you as a small builder
If you're controlling excavation work, you should:
Plan the dig as seriously as temporary works
- Decide method, support (shoring/boxes/battering), plant to be used, and access/egress before you start.
- Get and interpret service information, scan, mark and agree safe dig methods and stand-offs.
Provide and use proper support
- Don't rely on "good ground" -- use trench boxes or shoring in most utility-type trenches unless you've got a very solid case not to.
- Keep spoil, materials and plant back from the edge -- HSE guidance shows how surcharge at the edge contributes to collapse.
Arrange competent inspections
- Nominate someone competent to inspect and record -- daily before use and after events.
- Act quickly on any signs of movement, cracking, water ingress -- that's your early warning.
If you're working in someone else's excavation and it's clearly unsupported, too close to services with no information, or showing obvious movement, you're within your rights to refuse to go in until it's made safe.
You don't need to be a geotechnical engineer, but you do need to assume the sides can go at any time unless you've controlled the risk -- and treat services as live and dangerous until you've proved otherwise.
What to do next
- Get utility plans and scan the ground for services before every dig -- not after you've hit something.
- Use trench boxes or shoring in utility-type trenches unless you've got a very solid case not to -- don't rely on "good ground".
- Keep spoil, materials and plant well back from the edge of any excavation.
- Make sure someone competent inspects the excavation at the start of every shift and after any heavy rain or unusual event.
- If you're working in someone else's unsupported trench and it's showing movement, get out and refuse to go back in until it's made safe.
Sources
- Construction (Design and Management) Regulations 2015 -- planning, managing and monitoring excavation work.
- Health and Safety at Work etc. Act 1974 -- general duties.
- Management of Health and Safety at Work Regulations 1999 -- risk assessment duties.
- HSE -- Excavations: legal duty to prevent danger, use of support/battering, and competent inspections.
- Underground services guidance (HSG47) -- safe digging, plans, scanning and permit-to-dig concepts.
Disclaimer
This guide is general information for small UK construction businesses and trades, not formal legal or geotechnical advice.
SiteKiln is not a law firm and this page is not a substitute for getting advice on your specific situation.
Health and safety law and HSE guidance on excavation safety are updated from time to time, and how they apply will always depend on the exact facts on your job, the ground conditions and your role.
If you're dealing with an excavation collapse, service strike, enforcement notice or complex excavation near buildings/services, get specific advice from a competent geotechnical engineer, temporary works designer and/or solicitor before you make big decisions.
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