ÆANDREW EDWARD & CO.
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For adjoining owners

Your neighbour is digging.
This is the one to take seriously.

Basement excavation and deep underpinning are the highest-risk works the Party Wall etc. Act 1996 covers. Removing ground from beside a building changes how that ground supports your foundations, and the consequences show up as settlement, cracking and distortion, sometimes months after the work has finished.

If a Section 6 notice has been served on you, you have 14 days to respond. If excavation is already under way and you were never served, treat that as urgent and call us today.

Speak to a party wall surveyor todayI've been served a notice
Why excavation is different

The risk is under your house, not next to it.

With most party wall work the risk is local: a beam bearing badly, a bit of cracking around a new opening. Excavation is not local.

Your foundations rely on the ground beside and beneath them for lateral restraint and bearing. Take that ground away, even temporarily, even in bays, and the soil beneath your building will move to fill the space. On clay it may heave or shrink with moisture change. On sand it can run. On made ground it may do something else entirely. Lowering groundwater to keep an excavation dry pulls water out of soil well beyond the site boundary, and consolidation follows.

None of that means a basement next door will damage your home. Thousands are built safely every year. It means the difference between safe and unsafe lies in engineering detail, sequencing, temporary works, bay widths, dewatering, monitoring, and that detail deserves an independent professional reading it with your building in mind.

Ground relaxation

Removing lateral support lets soil move towards the excavation. Your foundation follows it. Usually small, occasionally not.

Dewatering and consolidation

Pumping to keep the dig dry draws down groundwater across a wide area. Soils consolidate as water leaves, and buildings settle with them.

Underpinning sequence

Underpinning is safe when done in short, properly sequenced bays with adequate temporary support. Too many bays open at once and the wall above is unsupported.

Vibration

Piling, breaking out and compaction transmit energy through the ground. Older lime-mortared and rubble-filled walls tolerate it poorly.

Heave

On clay, removing overburden lets the ground swell upward over months or years. Damage from heave often appears long after everyone has gone home.

Services and drainage

Shared drains, water mains and gas services in the excavation zone can be disturbed. A leaking drain beneath a foundation causes its own settlement.
What we insist on

What a basement Award should actually contain.

A generic Award with the word "basement" inserted is not adequate for this kind of work, and we see them.

These are the provisions we press for when acting for an adjoining owner next to an excavation. Each one exists because its absence has caused a real problem for someone.

Have the scheme reviewed. Free to youRead your rights as an adjoining owner

The provisions that matter

  • A defined temporary works design, prepared by a competent engineer and issued to both surveyors before excavation begins. Not developed on site.
  • Sequencing and bay widths stated explicitly, with a maximum number of bays open at any one time and a minimum curing period before the next.
  • Movement monitoring with trigger values. Targets on your building, read at defined intervals, with amber and red thresholds and a stated action at each.
  • A groundwater and dewatering strategy, including what happens if flows exceed expectation.
  • A thorough schedule of condition covering interiors, elevations, drives, paths, boundary walls and outbuildings, with crack widths recorded.
  • A CCTV drainage survey before and after where drainage runs near the excavation.
  • Security for expenses where appropriate. Under section 12 an adjoining owner may request security before works begin, which matters if the building owner is a special purpose vehicle with no assets.
  • Defined working hours and access controls, and a named site contact for both surveyors.

Section 12 security for expenses is underused, and basements are exactly what it is for

If your neighbour's development is being carried out by a company formed for that project, an obligation to make good is only worth as much as the company behind it. The Act lets an adjoining owner require security, typically a sum held in escrow, before the works begin. It has to be requested at the right time, which is another reason to appoint a surveyor early rather than after the digging starts.
What to do

If a basement is planned next door.

  1. Do not consent to a Section 6 notice without advice

    Free to ask
    Consenting to an excavation notice means no Award, no schedule of condition, no monitoring and no agreed method. For a basement that is a poor trade at any price, and it costs you nothing to dissent.

  2. Appoint your own surveyor

    Building owner normally pays
    This is the case where a single agreed surveyor is least appropriate. You want two professionals reading the same structural design, and a third surveyor available if they disagree.

  3. Ask for the full design package

    Before excavation
    Structural drawings, calculations, ground investigation report, temporary works design and method statement. If a ground investigation has not been carried out, that is itself worth raising.

  4. Get the schedule of condition done properly

    Before any work
    Interiors, elevations, boundary structures and drainage. On an excavation matter this document is doing more work than on any other kind of case.

  5. Make sure monitoring has teeth

    In the Award
    Readings without trigger values and a stated stop-work threshold are just paperwork. The Award should say what happens at amber and what happens at red.

Basement and excavation questions

Can I stop my neighbour digging a basement?

Not simply because you object. The Party Wall etc. Act 1996 gives building owners the right to excavate subject to notice and to an Award, and planning permission is a separate question again. What you can do is insist the work is governed by a properly drafted Award. With monitoring, movement triggers, agreed temporary works, defined sequencing and a duty to make good. In practice a well-drafted Award constrains a basement scheme far more effectively than an objection ever would.

What are the 3 metre and 6 metre rules?

Section 6(1) applies where excavation is within 3 metres of your building and will go deeper than the bottom of your foundations. Section 6(2) applies within 6 metres where the excavation cuts a line drawn downwards at 45 degrees from the bottom of your foundations. Either engages the Act, and the notice must be accompanied by plans and sections showing the depth and position of the proposed excavation. Both are frequently missed on schemes that only notice the party wall itself.

Will they need to underpin my house?

Sometimes, and that is not necessarily alarming. Underpinning is a controlled, well-understood technique. What matters is the sequence, the bay widths, the pin lengths, the temporary support and the monitoring regime. Those details belong in the Award rather than being left to the contractor on the day, and getting them right is exactly what your appointed surveyor is there for.

What is movement monitoring and should the Award require it?

For a basement adjacent to your property, in our view yes. Monitoring means fixed targets or levelling studs installed on your building and read at intervals through the works, so movement is measured rather than argued about. A good Award sets trigger values: at amber the contractor reviews the method, at red the works stop and the surveyors reconvene. Without triggers, monitoring is just data nobody acts on.

Who pays for all of this?

The building owner. Section 11 puts the cost of the works and the reasonable fees of both surveyors on them, and on a basement scheme that properly includes the extra time your surveyor spends on structural review and monitoring. A basement is precisely the case where the free protection is worth the most.

What about noise, dust and lorries?

The Award can regulate working hours, deliveries, wheel washing, dust suppression and access. It cannot make a basement excavation quiet. Where nuisance goes beyond what the Award contemplates, that is a matter for the local authority's environmental health team under the Control of Pollution Act 1974 rather than for the party wall surveyors, and we will tell you where the line falls.

Have the excavation design read by someone on your side of the wall.

Send us the notice and whatever drawings you have been given. We will tell you what is actually proposed, what the risks to your property are, and what the Award needs to control, at the building owner's expense, not yours.

  • The building owner normally pays your surveyor's reasonable fees
  • A named surveyor on your case from start to finish
  • We will tell you honestly if you do not need us
Appoint us as your surveyorTalk to us first, freeor call 01174420259

No card details. No obligation. Nothing is final until you sign the appointment. A member of our office team reads every message, and a surveyor replies, usually within one working day.

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