Project Type
Basement Conversion
Duration
24 weeks
Project Value
£195,000
The Challenge
Westminster's basement policy in conservation areas requires a structural method statement demonstrating that neighbouring properties will not be affected by excavation. Two of the four adjoining properties had their own basements, making the structural challenge particularly acute. Party wall awards were required with all four neighbours, one of whom initially appointed a dissenting party wall surveyor.
Our Solution
We appointed a structural engineer with specific Westminster basement experience who designed a reinforced concrete underpinning scheme using a sequential bay method to minimise movement in adjacent structures. Settlement monitoring pins were installed on all neighbouring properties before work commenced, with weekly readings throughout. The dissenting party wall surveyor's concerns were addressed through a revised structural method statement and the award was agreed without tribunal.
Results
- ✓Westminster planning consent obtained in 14 weeks
- ✓Four party wall awards agreed — all without tribunal
- ✓Settlement monitoring confirmed zero measurable movement in adjacent structures
- ✓90m² of basement space created across four rooms
- ✓Spa bathroom with steam room, sauna, and plunge pool
- ✓Temperature-controlled wine cellar with Eurocave racking for 800 bottles
- ✓Estimated property value uplift: £350,000
Key Features
- ✓Westminster conservation area planning consent
- ✓Sequential bay underpinning — four party wall awards managed
- ✓Settlement monitoring throughout construction
- ✓Spa bathroom — steam room, sauna, plunge pool
- ✓Temperature-controlled wine cellar — Eurocave racking
- ✓Natural light via new rear lightwell and glass floor panel
Specification
| Item | Specification |
|---|---|
| Underpinning | Mass concrete sequential bay underpinning, 300mm bays, 1m deep |
| Waterproofing | Sika Type C cavity drain system with dual sump pumps and high-level alarm |
| Spa pool | Leisureplan stainless steel plunge pool, 3.5m × 1.8m, chilled and heated |
| Steam room | Helo steam generator, custom glass and ceramic tile enclosure, teak bench seating |
| Wine cellar | EuroCave Performance 283 cooling unit, custom American oak racking, LED display lighting |
| Glass floor panel | Structural glass floor panel, 1200×900mm, 50mm thick, over staircase void |
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