If your project involves new foundations close to a neighbour’s building, you may hear a party wall surveyor refer to “foundation bays”, “hit and miss excavation”, or “sectional digging”. Building owners often dislike the idea because it can be slower and more costly than digging a full trench in one go. Adjoining owners tend to welcome it because it reduces risk.
At Simple Survey, we include a hit-and-miss bay approach in our Party Wall Awards where foundations are being formed alongside an existing structure and ground stability is a reasonable concern. Our reasoning is straightforward: the slower method is often the safer method, and safety is what prevents damage and disputes.
This article explains what foundation bays are, why they are used, how they reduce movement risk, and what they mean in practice for both building owners and adjoining owners.
1) Why foundations become a party wall issue
The Party Wall etc. Act 1996 applies in England and Wales and provides a framework for certain works that may affect neighbouring property. Foundations close to a neighbour’s building are typically relevant because excavation can affect:
- the support of surrounding ground,
- the stability of nearby foundations, and
- the risk of settlement or movement.
This is why excavation close to neighbouring buildings commonly falls under Section 6 of the Act (adjacent excavation). Many foundation projects also sit alongside other notifiable works, such as:
- new boundary walls (often linked to Section 1), and/or
- works to an existing party wall/party structure (often linked to Section 2, with notice served under Section 3).
Where written consent is not provided, surveyors may be required under the Act’s dispute procedure (commonly associated with Section 10), and an Award may be produced. This is where foundation excavation safeguards—such as bay digging—are typically set out.
2) The Party Wall process: Notice → Response → (if needed) Award
For beginners, the foundation-related party wall route is easiest to understand in three stages:
Stage 1: Notice
If excavation is notifiable, the building owner serves a Section 6 notice (commonly at least 1 month before excavation begins). If other notifiable works exist, there may be additional notice requirements.
Stage 2: Response (14 days)
The adjoining owner can consent or dissent (or not respond). If there is no written consent, the matter moves into the formal route.
Stage 3: Award where required
Where surveyors are appointed, the Award will commonly include practical safeguards to reduce risk. Foundation bay excavation is one of the most common and effective safeguards where foundations run close to existing structures.
3) What “hit and miss” foundation bays actually mean
A “hit and miss” bay method is a controlled way of excavating a foundation trench in short sections rather than in one continuous open trench.
In plain terms, it works like this:
- A short section is excavated—often around 1 metre in length (this is sometimes called a “bay”).
- That bay is immediately filled—usually with concrete to the required foundation level.
- A gap is left unexcavated—often another short section (for example, 1 metre) next to it remains intact.
- The next bay is excavated only after the previous bay has been filled and has stabilised sufficiently to act as support.
So the trench is excavated in an alternating pattern:
- dig 1m → fill 1m → leave 1m intact → dig next 1m → fill next 1m, and so on.
This method is slower because the contractor cannot simply trench everything open in one run. However, it reduces the amount of ground that is unsupported at any one time.
4) Why building owners often dislike bay digging (and why it is still used)
From a building owner’s perspective, the objections are predictable:
- It takes longer: the excavation cannot proceed as quickly.
- It can cost more: more careful sequencing, more labour time, and sometimes more site management is required.
- It feels “over-cautious”: particularly where the owner believes their builder is experienced.
These concerns are understandable. But party wall is not about how confident the building owner feels. It is about managing risk where the neighbour’s property could be affected.
The most expensive party wall outcome is not “a cautious excavation method”. The most expensive outcome is avoidable movement, damage, and dispute.
5) Why bay digging reduces movement risk
Excavation removes support from the ground. If a long trench is left open alongside an existing structure, the ground can soften, shift, or locally collapse—particularly in poor ground or wet conditions.
The hit-and-miss approach reduces risk because:
- Less ground is open at one time
Only a short bay is excavated at any moment. The surrounding ground remains largely supported. - Filled bays act as early support
Once a bay is poured, it provides stability along the line, helping resist movement. - The intact “miss” sections support the trench edges
The unexcavated sections act as temporary buttresses while adjacent bays are formed.
This is exactly why bay digging is used when foundations are constructed close to an existing structure: it reduces the opportunity for ground movement to develop.
6) When bay digging is commonly required in party wall Awards
At Simple Survey, we commonly require a hit-and-miss bay approach in our Awards when:
- foundations are being dug alongside or close to an existing neighbouring structure, and
- the excavation is notifiable under the Act (commonly Section 6), and
- leaving a continuous trench open would create a foreseeable stability risk.
This approach is not about punishing the building owner. It is about making the excavation method proportionate to the risk created by proximity.
If the works are not alongside an existing structure in a way that creates meaningful risk, the method may not be necessary. But where it is alongside an existing structure, it is a sensible control measure.
7) What this means for building owners in practical terms
If bay digging is required, the best approach is to treat it as a programme item and plan for it:
- Discuss the method with your contractor early
If your builder is unaware, they may price incorrectly or resist later. - Sequence deliveries and labour accordingly
Bay digging often requires a more controlled pour schedule. - Avoid leaving open excavations
Bay digging works best when excavation and filling are tightly coordinated.
Most importantly, recognise the commercial reality: a modest increase in excavation cost is often cheaper than the consequences of movement and dispute.
8) What this means for adjoining owners
For adjoining owners, bay digging provides practical reassurance. It reduces the likelihood that:
- the ground next to your foundations will be left unsupported,
- long trenches will remain open near your property,
- and avoidable instability will develop.
It also gives you a clear standard: you can understand what is meant by “controlled excavation” and you can expect the works to follow that sequence.
If you observe long continuous excavation left open alongside your property when bay digging is required, you should raise it promptly through the proper party wall channel—particularly where surveyors are appointed.
9) A professional note on proportionate drafting
A bay method should be written clearly and practically in an Award:
- the typical bay length,
- the sequence (excavate, fill, leave intact, repeat),
- and what happens if conditions require temporary support.
The goal is to create a method that is workable on site and genuinely reduces risk—rather than a clause that reads well but is ignored.
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If your project involves foundations close to a neighbour’s building, contact Simple Survey. We draft practical Party Wall Awards that reduce risk without unnecessary theatre—including hit-and-miss foundation bay methods where they are sensible and proportionate. Our aim is simple: protect both owners, keep the works controlled, and avoid avoidable damage and disputes. We are built around low-cost fixed-fee pricing and aim to be the UK’s cheapest party wall surveyors, without compromising professional standards.
Get in touch with Simple Survey and let us keep your foundations approach safe, structured, and properly managed from day one.