Case studyChelsea · SW3
Chelsea townhouse, opened up and fitted out
A tired Chelsea townhouse with no room to build up. So we went down, under the whole house.
Nick Jeffries on Bloomberg, 2015: London’s Last Super-Basement
- Where
- Chelsea, SW3
- The home
- A late 19th century terraced house
- Size
- 4,300 sq ft
- Below ground
- About 1,200 sq ft, one floor
- Planning
- Granted November 2012
- Value band
- £1m to £2.5m
- Completed
- 2015
- On site
- 13 months
- Joinery
- Slater Joinery
i The brief
No room to build up or out. So we went down.
A late 19th century terraced house, in a Chelsea conservation area.
The house was tired. It had only a small lower floor, at the back.
The roof stayed at its height.
The rear extension could grow by just 0.6 metres.
So the new space had to come from below.
Planning permission came through in November 2012.
ii Going down
A new lower floor under the whole house.
The dig went about 3.6 metres below the ground floor.
It runs under every room and under the front garden.
The house sits on gravel over London Clay. Ground water lay well below the new floor.
The party walls were underpinned in reinforced concrete, one metre at a time.
No two sections side by side were dug within 48 hours.
Underpinning kept more room inside than a piled wall would have.
A 350 mm concrete slab went across the whole floor.
A drained membrane and a sump pump keep it dry.
A chartered structural engineer supervised the work throughout.
One floor down, under every room.
The gym, the stair and the family room.
The house stayed standing while a whole new floor went in beneath it.
iii During the build
Steel in, ground out.
Our own photographs from site, taken during the build.
New steels went in to carry the house above.
Each underpinning bay was reinforced, then cast.
The slab reinforcement went down across the whole floor.
Two photographs have been edited for health and safety.
The builders now wear the black NU helmet and vest.
iv The interior design
Eleven ways down. One stair.
A new floor needs a stair worth walking down.
Eleven stair designs were drawn in 2014.
A steel spine. A curve. Open treads. Treads set into the wall.
The built stair follows the last idea.
Marble treads are set into the wall, behind frameless glass.
The handrail is wrapped in leather.
The four designs below are options. They are not photographs.
v The finished house
Marble, glass and joinery, top to bottom.
The kitchen sits under a walk on glass rooflight, over six metres long.
A new stone fireplace anchors the drawing room.
Joinery by Slater Joinery runs through the house.
Down below, the gym is lined with mirrors between lit pilasters.
vi The team
Who built it.
- The studio
- NU Projects, founded by Nick Jeffries
- Basement, build and fit-out
- NU Projects
- Joinery
- Slater Joinery
The scope Basement under the full footprint Structural works Interior design Joinery Full fit-out Project management
Services on this jobDesign and buildBasementsInterior designBespoke joineryConstruction project management
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