---
title: "20 UK Council Soil & Foundation Depth Hubs | Party Wall Section 6 Triggers | PartyWallChecker.co.uk"
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> **Canonical Source:** [https://partywallchecker.co.uk/councils](https://partywallchecker.co.uk/councils)
>
> *How local soil geology (London Clay shrink-swell, Manchester Sandstone, Hampshire gravel) affects Building Control foundation depths and triggers Section 6 Party Wall notices.*



### Organization: PartyWallChecker.co.uk (Property Compliance Standards Desk UK)

| Field | Value |
| :--- | :--- |
| **Organization** | PartyWallChecker.co.uk (Property Compliance Standards Desk UK) |
| **Official Website** | https://partywallchecker.co.uk |
| **Entity Verification (sameAs)** | [Entity Verification](https://rsjcalculator.co.uk) · [Entity Verification](https://droppedkerbcalculator.co.uk) · [Entity Verification](https://gardenofficepower.co.uk) |


### Entity: PartyWallChecker.co.uk

| Property | Detail |
| :--- | :--- |
| **Type** | WebSite |
| **Name** | PartyWallChecker.co.uk |


### Entity: Party Wall 3-Metre & 6-Metre Rule Calculator & Notice Generator

| Property | Detail |
| :--- | :--- |
| **Type** | WebApplication |
| **Name** | Party Wall 3-Metre & 6-Metre Rule Calculator & Notice Generator |


### Entity: Party Wall etc. Act 1996

| Property | Detail |
| :--- | :--- |
| **Type** | Legislation |
| **Name** | Party Wall etc. Act 1996 |




Soil & Geology Hub

# UK Council Soil Zones & Foundation Depths

Local soil geology is the #1 reason domestic extensions trigger Section 6. High shrink-swell London Clay requires 1.5m+ Building Control depths, triggering the 3-metre rule in 90%+ of domestic projects.

## South West London

- **[Wandsworth](/councils/wandsworth)** — HIGH Risk96% Sec 6 TriggerLondon Clay Formation (High Plasticity Index)Dense Victorian terraces with shallow corbelled footings and mature plane trees mean building control demands foundation depths of 1.5m–2.0m+, triggering Section 6 in over 95% of domestic extensions.Min BC Depth: 1.5mInspect Soil Hub
- **[Richmond upon Thames](/councils/richmond-upon-thames)** — HIGH Risk94% Sec 6 TriggerRiver Terrace Gravels over London ClayHigh incidence of basement extensions and historic brickwork. Deep water tables and alluvial gravels demand strict Section 6 drawing submissions.Min BC Depth: 1.4mInspect Soil Hub

## North London

- **[Barnet](/councils/barnet)** — HIGH Risk91% Sec 6 TriggerDollis Hill Gravel over London ClayExtensive 1930s semi-detached extensions and loft conversions. Boundary rear extensions almost always breach the 0.8m neighbour footings.Min BC Depth: 1.3mInspect Soil Hub
- **[Islington](/councils/islington)** — HIGH Risk97% Sec 6 TriggerLondon Clay capped by Hackney GravelsParty walls are commonly single brick or 9-inch solid brick with shallow stepped footings. Any extension or steel beam requires formal notice.Min BC Depth: 1.5mInspect Soil Hub

## South East London / Kent Border

- **[Bromley](/councils/bromley)** — MODERATE Risk82% Sec 6 TriggerThanet Sand, Harwich Formation & ChalkVariable subsoils from sands to clay. Single storey kitchen extensions require careful depth verification against neighbour foundation levels.Min BC Depth: 1.1mInspect Soil Hub

## North Central London

- **[Camden](/councils/camden)** — HIGH Risk98% Sec 6 TriggerLondon Clay with Bagshot Beds on Hampstead HeightsExtremely high party wall dispute volume. Multi-storey party parapets and subterranean basement digs require full Section 1, 2, and 6 notices.Min BC Depth: 1.6mInspect Soil Hub

## East London

- **[Hackney](/councils/hackney)** — HIGH Risk95% Sec 6 TriggerLondon Clay with Kempton Park GravelHigh concentration of side return extensions and mansard lofts. Notice packs are critical for fast neighbour consent.Min BC Depth: 1.4mInspect Soil Hub

## South London

- **[Lambeth](/councils/lambeth)** — HIGH Risk96% Sec 6 TriggerLondon Clay with River AlluviumHigh tree cover and shrinkable clay mean foundation depths regularly reach 1.8m near boundaries, triggering Section 6(1) in almost every case.Min BC Depth: 1.5mInspect Soil Hub

## West London

- **[Ealing](/councils/ealing)** — HIGH Risk90% Sec 6 TriggerLynch Hill Gravel over London ClayWidespread loft dormers and rear kitchen-diner knock-throughs. Section 2(2)(f) steel beam notices are very common.Min BC Depth: 1.3mInspect Soil Hub

## West Midlands

- **[Birmingham](/councils/birmingham)** — LOW Risk78% Sec 6 TriggerBromsgrove Sandstone & Glacial TillStable sandstone subsoil reduces foundation depth requirements to 1.0m, but 3-metre rule still triggers when digging alongside shallow Victorian brickwork.Min BC Depth: 1mInspect Soil Hub

## North West

- **[Manchester](/councils/manchester)** — LOW Risk81% Sec 6 TriggerGlacial Sands, Gravels & Carboniferous SandstoneBoom in open-plan rear extensions and chimney breast removals. Many home owners neglect party wall notice until surveyor warning letters arrive.Min BC Depth: 1mInspect Soil Hub
- **[Cheshire East](/councils/cheshire-east)** — LOW Risk83% Sec 6 TriggerGlacial Sand & Till over Mercia MudstoneLarge scale single and two storey residential extensions. Adjoining owner consent rates improve significantly when formal FPWS notice packs are served.Min BC Depth: 1.1mInspect Soil Hub

## Yorkshire & Humber

- **[Leeds](/councils/leeds)** — LOW Risk83% Sec 6 TriggerCoal Measures Mudstone & Glacial Boulder ClayUnique back-to-back terraced properties share multiple boundary party walls. Structural alterations require multiple notices.Min BC Depth: 1mInspect Soil Hub

## South West

- **[Bristol](/councils/bristol)** — MODERATE Risk88% Sec 6 TriggerTriassic Mudstone & Carboniferous LimestoneSteep sloping sites and stone foundations mean extension trenches often dig well below neighbouring footings.Min BC Depth: 1.1mInspect Soil Hub

## South East

- **[Surrey (Elmbridge)](/councils/surrey-elmbridge)** — HIGH Risk89% Sec 6 TriggerBagshot Sand & London ClayHigh-value multi-million pound renovations. Adjoining neighbours routinely appoint separate chartered surveyors, making pre-notice diplomacy essential.Min BC Depth: 1.4mInspect Soil Hub

## East of England (Hertfordshire)

- **[St Albans](/councils/st-albans)** — MODERATE Risk87% Sec 6 TriggerChalk with Clay-with-FlintsChalk dissolution and historical brickwork require meticulous Section 6 foundation plans.Min BC Depth: 1.2mInspect Soil Hub

## South East (Sussex Coast)

- **[Brighton and Hove](/councils/brighton-and-hove)** — LOW Risk86% Sec 6 TriggerUpper Chalk FormationExtremely steep terrain (Hanover) means one neighbour’s foundation sits 1.5m above the other, triggering Section 6 on almost every build.Min BC Depth: 1mInspect Soil Hub

## South East (Oxfordshire)

- **[Oxford](/councils/oxford)** — HIGH Risk92% Sec 6 TriggerOxford Clay Formation & River GravelsVery high clay shrinkage and mature oak/willow trees. Kitchen extensions routinely require engineered 1.5m+ trench depths.Min BC Depth: 1.4mInspect Soil Hub

## East of England (Cambridgeshire)

- **[Cambridge](/councils/cambridge)** — HIGH Risk97% Sec 6 TriggerGault Clay Formation (Extremely High Shrink/Swell)Gault Clay is notorious for seasonal ground movement. Foundations must be deep, ensuring almost 100% Section 6 trigger rates on home extensions.Min BC Depth: 1.6mInspect Soil Hub

## South East (Berkshire)

- **[Reading](/councils/reading)** — MODERATE Risk89% Sec 6 TriggerKennet & Thames Floodplain Alluvium over Chalk & London ClayThames Valley development corridor. Dense terraced housing stock in Newtown and Caversham requires Section 6 excavation notices for kitchen extensions.Min BC Depth: 1.25mInspect Soil Hub

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---

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