Basement Conversion, Highgate N6
Full basement excavation and conversion beneath a detached Edwardian property in Highgate Village, creating 85 sqm of habitable space including a home cinema, gym and guest suite. 14-month specialist programme with complex underpinning.
Unlocking 85 sqm Beneath a Highgate Villa
This substantial detached Edwardian property in Highgate Village had no existing basement. The owners wanted to create a full-height habitable basement comprising a home cinema, gym, guest bedroom with en-suite and a utility-plant room.
Our structural engineer designed a full underpinning scheme using a contiguous piled wall system, allowing us to excavate to a clear internal height of 2.7 metres while minimising vibration risk. A Type C cavity drain membrane system with dual sump pumps provides waterproofing.
Natural light was introduced through three pavement-level lightwells, supplemented by circadian-tuned LEDs. A dedicated MVHR unit serves the basement level, maintaining fresh air and humidity control independently.
The cinema room features acoustic isolation with independent stud walls, a floating floor and acoustic ceiling tiles, creating a genuinely immersive environment with zero sound transfer to the rooms above.
Project Timeline
Site Investigation
Comprehensive ground investigation including boreholes and groundwater monitoring. Structural survey of existing foundations. Tree root protection assessment.
Structural Design
Contiguous piled wall scheme designed. Underpinning sequence planned. Waterproofing strategy specified.
Planning & Approvals
Planning application with Construction Management Plan. Building control application. Condition surveys of neighbouring properties.
Piling & Excavation
Mini-piling rig installed. 32 CFA piles installed. Bulk excavation followed by reinforced concrete floor slab.
Waterproofing & Services
Cavity drain membrane installed. Dual sump pump system with battery backup. First-fix M&E including MVHR and cinema pre-wire.
Fit-Out
Acoustic isolation for cinema room. Gym fit-out. Guest suite with en-suite. Ground floor reinstated.
Commissioning & Handover
Cinema AV system commissioning, MVHR balancing, sump pump testing and snagging. 10-year waterproofing guarantee.
What We Delivered
Full Basement Excavation
New-build basement beneath existing footprint: 85 sqm at 2.7m clear height using contiguous piled walls and sequential underpinning.
Home Cinema Room
Acoustically isolated cinema with 4K projector, 7.2.4 Dolby Atmos and tiered seating for eight.
Gym & Guest Suite
Fully equipped gym with rubber flooring and dedicated ventilation. Adjacent guest bedroom with en-suite.
Waterproofing & M&E
Type C cavity drain with dual sump pumps, battery backup and remote monitoring. Dedicated MVHR and underfloor heating.
Investment Breakdown
How the project budget was allocated across the major work packages.
Problems We Solved
Ground Conditions
High clay content soil with seasonal movement, plus a mature oak tree within the zone of influence.
Piled wall solution designed for clay heave. Tree protection plan agreed. Root barrier installed along excavation perimeter.
Zero Structural Damage
Excavating beneath a 120-year-old structure while maintaining the occupied upper floors throughout.
Phased underpinning with monitoring stations on each corner. Real-time movement data reviewed daily. 5mm tolerance never exceeded.
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Planning a Similar Project?
Whether you are considering a basement conversion, underpinning project or home cinema installation in Highgate, Hampstead or North London, our team can help.