Underpinning is one of the highest-risk categories of notifiable work under the Party Wall etc. Act 1996.
Done properly, it’s a safe, tightly controlled process; done casually, it can jeopardise neighbouring structures and stall your project.
Here’s the fully-fledged guide—legal duties, technical nuances, risk controls, and how surveyors keep everyone protected.
Where the Act gives the right to underpin
1) Section 2(2)(a): Works to a party wall/structure
“…to underpin, thicken or raise a party structure, a party fence wall, or an external wall which belongs to the building owner and is built against a party structure or party fence wall;”
If your scheme requires underpinning a party wall (or your wall that abuts a party structure), this is classic Section 2 work and requires a Party Structure Notice (minimum 2 months before works commence).
2) Section 6(3) & 6(5): Adjacent excavation and safeguarding
(3) The building owner may, and if required by the adjoining owner shall, at his own expense underpin or otherwise strengthen or safeguard the foundations of the adjoining owner’s building…
(5) …serve on the adjoining owner a notice… stating whether he proposes to underpin or otherwise strengthen or safeguard…
Where excavation triggers Section 6 (within 3 m and deeper than the neighbour’s foundations, or within 6 m crossing the 45° plane), you must give at least 1 month’s notice and explicitly state if underpinning/safeguarding is proposed.
In plain terms:
- You can lawfully underpin a shared wall (Section 2) and, if necessary, safeguard/underpin your neighbour’s wall (Section 6) at your cost.
- You must serve the correct notices and declare the intention to underpin.
The real-world complexity (and how to manage it)
Underpinning raises the risk profile—and surveyors will calibrate protections accordingly.
Typical underpinning methods you’ll see
- Mass concrete pins: Sequential pins beneath the wall; robust and common for domestic basements and deepened footings.
- Beam & base: Reinforced beams spanning between discrete bases; used where loads or ground variability demand it.
- Mini-piles with capping beam/needling: Useful where soil or access constraints make traditional pins impractical.
- Bailey “downward raising” approach (engineering strategy): Sometimes used to avoid “special foundations” issues at the boundary (design-team topic—speak to your engineer/surveyor early).
Special foundations caution: If any foundation includes an assemblage of rods or beams to distribute load and sits on/over the neighbour’s land, Section 7(4) requires the adjoining owner’s written consent. If they refuse, expect a redesign (e.g., mass-concrete). Your surveyor and engineer should plan for this scenario from the outset.
Core temporary-works and construction controls
- Sequencing: One pin at a time with strict curing intervals; no leap-frogging that undermines bearing capacity.
- Needles/props: To control load paths during excavation.
- Support windows: Open excavations are time-limited; awards typically require prompt concrete placement or temporary shoring.
- Vibration/dust/noise minimisation: Hand tools near sensitive interfaces, controlled breaking, dust containment, and agreed hours.
- Water management: De-watering and surface water control to prevent softening/instability.
Information surveyors typically require
- Final, construction-issue drawings (plans/sections, details, notes).
- Foundation/excavation method statements (step-by-step pins sequence and temporary works).
- Engineer’s calculations & risk assessment (including any movement thresholds and trigger levels).
- Programme (with critical hold points, inspections, and concrete cure periods).
- Insurance evidence (contractor and/or project cover appropriate to the risk).
The extra protections that often accompany underpinning
1) Advising Engineer
For higher-risk schemes (e.g., basements, deep pins, complex soil), the adjoining owner’s surveyor will often request an independent Advising Engineer to review the design/method and advise the surveyors.
Their role is technical assurance—not redesign—aimed at verifying adequacy and suggesting practical mitigations.
2) Security for Expenses (Section 12)
Given the consequences of a stalled or part-completed underpin, adjoining owners may request Security for Expenses—a sum held to cover:
- Making the neighbour safe if works stop;
- Reasonable professional costs tied to safeguarding;
- Potential urgent remedial needs.
Quantum and release triggers are agreed and written into the award.
Notices and timing snapshot
- Section 2 Notice (party structure works, including underpinning a party wall): Serve ≥ 2 months before works.
- Section 6 Notice (adjacent excavation): Serve ≥ 1 month before works, stating whether you propose to underpin/safeguard.
- Non-response path: If the neighbour doesn’t respond, surveyors can still be appointed under Section 10(4) and an award made.
- Award service & appeals: Awards are served forthwith; there’s a 14-day appeal window from service.
What your Party Wall Award will usually lock down for underpinning
- Authorisation for the underpinning (and any necessary safeguarding).
- Method & sequencing (including concrete pour windows and curing).
- Temporary works (needles, propping, supports).
- Access (dates, hours, boundaries, protections, reinstatement).
- Risk mitigations (materials handling, vibration limits, dust/noise controls, temporary weathering).
- Variation protocol (how changes are agreed before implementation).
- Damage resolution pathway and costs.
- Costs and fees under Section 10(13) (typically paid by the building owner).
Common pitfalls (and how to avoid them)
- Undeclared underpinning on the notice: Fix: declare it specifically on the Section 6 notice.
- Assuming consent to special foundations: Fix: design with a Plan B (mass concrete) if consent is refused.
- Inadequate temporary works: Fix: ensure the contractor’s method statement and AE review are in place before excavation starts.
- Open pins left too long: Fix: programme concrete placement with realistic curing and inspection windows baked into the award.
- Late drawings: Fix: issue the final construction pack to surveyors to avoid re-drafts and delays.
Get Underpinning Right, First Time
Underpinning needs crisp design, watertight notices and a rigorous award. We’ll liaise with your engineer, set proportionate protections, and keep your programme moving—without drama.
Email us: team@simplesurvey.co.uk
Simple, fixed fees. Nationwide coverage. RICS qualified.
Simple Survey — Fixed Nationwide Cost Chart (Guide)
| Service | What’s Included | Fixed Fee (incl. VAT) |
|---|---|---|
| Party Wall Notice (per Adjoining Owner) | Compliance check, drafting, service & response tracking | £25 |
| Agreed Surveyor Award | Single impartial surveyor acting for both owners | £300 |
| Building Owner’s Surveyor Award | Acting for the Building Owner in a two-surveyor route | £300 |
FAQ
Q1. Do I always need to underpin for a basement?
Not always; your engineer will assess soil, loads and neighbouring foundations. Where Section 6 is triggered, surveyors may still require safeguarding measures short of full underpinning.
Q2. Can my neighbour force me to underpin their wall?
If your adjacent excavation creates risk, Section 6(3) allows the adjoining owner to require you to underpin or otherwise safeguard at your expense where necessary.
Q3. Who pays for underpinning and the professional input around it?
The building owner pays for underpinning related to their works, plus the reasonable surveyors’ fees determined under the award. Additional expert input (e.g., Advising Engineer) is typically allocated to the building owner unless the award says otherwise.
Q4. What if I want reinforced (special) foundations under the party wall?
If reinforcement would sit on/over the neighbour’s land, written consent is required under Section 7(4). Without it, expect a mass-concrete alternative.
Q5. Can I start underpinning as soon as the award is served?
Only when the award permits and all statutory notice periods/pre-conditions (access protections, engineer sign-offs, etc.) are met.
Q6. My neighbour refuses access for underpinning—can the project proceed?
Where access is necessary in pursuance of the Act, Section 8 provides a legal right of access. The award will govern how that access happens (timing, protections, reinstatement).
Q7. What happens if the contractor deviates from the agreed method?
Raise it immediately with the surveyor(s). The award requires adherence to the time and manner of works; non-compliance can lead to enforcement and additional costs.