# Basement Construction

> Single-storey, double-storey and lightwell basement excavations under existing London homes.

## Overview

Basement construction under existing London townhouses, semi-detached and detached homes is high-margin, technically demanding work that HXL routinely delivers. Single-storey excavations under footprint, double-storey schemes, lightwell and sub-pavement vault construction in conservation-area streets. All schemes include temporary-works design, structural propping, BS 8102-compliant waterproofing, and party wall coordination across all affected neighbours.

## Capabilities

- Single-storey basement excavation under existing footprint
- Double-storey basement schemes
- Lightwell and sub-pavement vault construction
- Temporary works and propping design
- BS 8102 Type C cavity-drainage waterproofing
- BS 8102 Type A and Type B tanked waterproofing
- Underpinning to existing foundations
- Party wall award coordination across all neighbours

## Process

### 01. Survey & design

Ground investigation, structural engineering design, party wall service, planning consent where the scheme falls outside permitted development.

### 02. Excavation

Underpin, install temporary works, excavate, remove spoil, construct retaining walls.

### 03. Waterproofing & fit-out

BS 8102 system installation, M&E first fix, plant install, second fix and finishes.

### 04. Sign-off

Structural sign-off, Building Control completion, waterproofing system warranty, 12-month workmanship warranty.

## FAQ

**How much does a basement cost in London?**

Single-storey under footprint: £500k to £900k. Double-storey or lightwell: £900k to £1.5m+. Costs depend on access, ground conditions, party wall scope and finish specification.

**Where do you typically deliver basements?**

Across NW3 Hampstead, NW8 St John's Wood, W11 Notting Hill, W8 Kensington, SW3 Chelsea, N6 Highgate, and the surrounding prime-fringe boroughs. Conservation-area and Article 4 streets handled as a matter of course.

**Do you need planning for a basement?**

Most full basements need a planning application. Permitted development applies only to limited cases. Hampstead, Chelsea and Kensington have additional basement restrictions which we handle as part of the application.

**Do basements affect party wall obligations?**

Yes. Every basement scheme involves Party Wall Act service across the affected neighbours. We coordinate surveyor appointments and awards as part of the main contract.


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**HXL Construction Ltd** · Principal contractor and design & build firm · London and the Home Counties
Email: info@hxlconstruction.com · Phone: +44 7845 585147
Registered office: 102 Vine Lane, Uxbridge, London UB10 0BE
Canonical: https://hxlconstruction.co.uk/services/basement-construction