Excavation near you

The reference document is HSG47, Avoiding danger from underground services, published by the Health and Safety Executive in its third edition in 2014. It addresses everyone involved in commissioning, planning, managing and carrying out work on or near underground services, along with the owners and operators of those services, and it sets out the hazards of working near buried services and how to reduce both the direct risk to people and the indirect risk that comes from damaging a service.

Its structure is the useful part for a homeowner, because it reduces to three elements that should be visible in any competent contractor's method. Plan the work, which means obtaining the service owners' plans before anyone arrives rather than looking for them afterwards. Locate and identify buried services, which means using detection equipment on site and marking what is found, not treating the plans as a map of reality. And excavate safely, which means digging in a way that assumes something is there until it is proved otherwise. HSE's construction guidance makes the consequences plain: many serious accidents have occurred when buried services have been damaged during excavation work, contact with electricity cables can cause explosions and burns, and damaged gas pipes can lead to fire.

In a garden this matters more than people assume, because domestic plots accumulate unrecorded services: a cable to a shed run in by a previous owner at whatever depth the trench happened to be, a water pipe to an old greenhouse, a gas supply crossing to a garage. None of those appears on a utility plan. The practical questions to ask a contractor are whether they will obtain plans before starting, what locating equipment they use, and how they intend to work in the areas where something has been detected.

In England and Wales, a dig close to a neighbour's building and deeper than its foundations triggers a statutory notice. Section 6 of the Party Wall etc. Act 1996 catches excavation, or excavation for and erection of a building or structure, within three metres measured horizontally from any part of an adjoining owner's building or structure where the work will go to a lower level than the bottom of their foundations, and again within six metres where the work would meet a plane drawn downwards at forty-five degrees to the horizontal from the bottom of those foundations.

What the notice has to contain is worth knowing before you draft one, because an incomplete notice is not a notice. The section requires the building owner to indicate their proposals and to state whether they propose to underpin or otherwise strengthen or safeguard the foundations of the adjoining owner's building or structure, and to accompany the notice with plans and sections showing the site and depth of any excavation and the position of any proposed building or structure. It must be served at least one month before beginning to excavate.

The timetable then works against silence. If the adjoining owner does not serve a notice indicating consent within the period of fourteen days beginning with the day the notice was served, they are deemed to have dissented and a dispute is deemed to have arisen — at which point surveyors are appointed and the matter is settled by an award. Neighbours often do nothing rather than object, so a homeowner planning on a friendly conversation should budget for the surveyor route anyway. The Act does not extend to Scotland or Northern Ireland, where the relationship with an adjoining owner is governed differently, so take advice locally rather than serving an English notice.

HSE's position on collapse is uncompromising: no ground can be relied upon to stand unsupported in all circumstances. That is why the decision about temporary support — trench sheets, props, boxes or battering the sides back to a safe angle — is made before digging starts, and why the equipment is expected to be on site before the machine begins rather than fetched when the sides start to move. A collapse does not need a deep trench to be fatal; a cubic metre of soil is heavy enough.

Regulation 22 of the Construction (Design and Management) Regulations 2015 puts that into law. It requires that all practicable steps be taken to prevent danger to any person, including ensuring that no excavation or part of an excavation collapses, with support or battering provided where necessary. It also requires inspection by a competent person at the start of every shift, after any event likely to have affected stability, and after any unintended fall of material, with written reports recording the hazards identified and the action taken.

The other hazards on a domestic site are the mundane ones. HSE expects substantial barriers at excavation edges — guard rails with toe boards, or trench box systems standing proud of ground level — to stop people falling in, and warns about material falling in from spoil heaps and plant working too close to an open edge. In a small garden, where the excavation, the spoil and the route to the skip are all within a few metres of each other, these are not theoretical constraints but the reason the job takes longer than the volume suggests.

Depth, access and disposal set the figure. The variables are the volume to be removed and how far it has to be carried before it reaches a vehicle, whether a machine can get to the dig or the work is by hand, the ground conditions and whether obstructions such as old foundations or hardcore are likely, the depth and therefore the support arrangements required, whether buried services are known to cross the area, whether a party wall notice and possibly a surveyor's award are in the programme, and how much reinstatement follows. Two contractors can quote very different figures for the same hole because one has assumed clean ground and easy access and the other has not.

LokalMatch is the introduction step. Describe the dig once with your postcode — roughly how deep and how big, what it is for, how a machine would reach it and how close it is to a neighbour's building — and excavation contractors and groundworkers covering your area contact you. The homeowner pays nothing; the professionals pay for the requests they receive. LokalMatch carries out no work, sets no prices and does not vet, rank or recommend anyone who responds, so checking insurance, asking how buried services will be located and confirming who is serving any party wall notice is your part of it.