DRAKEFIELD HOUSE
Whole-House Transformation with Full-Footprint Basement
Tooting, South West London
INTRODUCTION
Studio MASS delivered the complete technical design, Building Regulations package, fire strategy and contract administration for a whole-house transformation of a mid-terrace Victorian villa in Tooting, South West London. The project added a full-footprint basement of 100 m² beneath the existing house and remodelled the ground and first floors across a further 170 m² of active works.
The loft, containing two children's bedrooms and a family bathroom, was left largely untouched.
Construction cost was circa £750,000, excluding the client-supplied kitchen, fixtures and fittings. Completed spring 2024.
WHAT THE PROJECT INVOLVED
The clients, a young professional couple, a doctor and a radiologist, owned a three-storey Victorian mid-terrace in Tooting. The house had a disjointed ground floor, a master bedroom in the wrong position, and no room for the family's growing needs. Planning permission for a full-footprint basement excavation and single-storey rear extension had already been secured by a separate architect before Studio MASS's appointment.
Studio MASS was brought in halfway through Phase 1, the basement structural works, after construction had begun without a technical drawings package or Building Regulations submission. The scope Studio MASS delivered included a full measured survey of the as-built structure, a complete Building Regulations package submitted while construction was underway, design of the rear kitchen extension (which had been approved in outline but left undetailed), a fire strategy for the open-plan escape route, tendering and appointment of the Phase 2 fit-out contractor, and five months of contract administration and site monitoring.
The project ran in two phases with two separate contractors: a specialist basement contractor for the structural shell, and Turnkey Contractors, appointed by Studio MASS via tender, for the Phase 2 fit-out, finishes, and mechanical and electrical works.
HOW MUCH DOES A BASEMENT COST UNDER A VICTORIAN TERRACE IN LONDON?
The structural shell of the basement at Drakefield Road, including excavation, temporary propping of the party walls on both sides, concrete retaining walls and ground-bearing slab, cost approximately £500,000 for a 100 m² footprint. That is approximately £5,000 per m² for the structural shell alone, before any fit-out, finishes or services.
The fit-out of the full house (basement, ground floor and first floor, approximately 270 m² of active works) was completed by a separate contractor for approximately £250,000 plus VAT, excluding the client-supplied kitchen, fixtures and fittings. Total construction cost was circa £750,000.
The basement was excavated beneath a mid-terrace with party walls on both sides, requiring staged temporary structural propping throughout. A small electric digger was lowered through the front bay window opening to work in the excavation below, removing the risk of diesel fumes for workers, and a conveyor system removed spoil to the street, minimising disruption to the pavement and neighbouring properties.
HOW DID YOU GET LIGHT INTO A BASEMENT UNDER A TERRACE HOUSE
Two lightwells, front and rear, bring natural daylight into the basement at Drakefield Road, turning what could have been a dark storage level into genuinely habitable living space. The rear lightwell is spanned by a glazed bridge connecting the lower level to the rear garden terrace, maintaining both daylight and a sense of connection to the outside.
The basement rooms are treated as fully habitable spaces throughout: a gym, a home cinema and second living room, a home office, a utility room with laundry and storage, a shower room, and a plant room. The front room, used as the radiologist's home office, is designed to be easily darkened for reviewing clinical scans, and multiple lighting circuits allow independent control of every zone.
HOW DO YOU MAKE AN OPEN-PLAN BASEMENT STAIRCASE COMPLY WITH FIRE REGULATIONS?
The central staircase linking the basement to the ground-floor dining room is open to the main living spaces, so it is not enclosed within a protected stairway enclosure. To make this compliant with Building Regulations, Studio MASS designed a fire-engineered escape strategy.
The solution has two parts: a residential sprinkler system covering the open escape route and the full basement level, and a full-height fire door on a magnet linked to the fire alarm. Day to day, the door sits open, preserving the visual connection between the original tiled entrance corridor and the garden view beyond. The moment the alarm activates, the magnet releases and the door closes, protecting the escape route. This is a fire-engineering approach rather than a standard protected enclosure, and it is what made the open-plan layout achievable while remaining fully compliant.
Coordinating the sprinkler first fix required careful sequencing across both the basement (straightforward, as the structure was open) and the ground floor, where pipes had to be threaded through the floor void after the original timber joists and floorboards were removed.
WHAT HAPPENED TO THE GROUND FLOOR?
The entire ground floor was stripped back to structure. The original Victorian timber joists and floorboards were removed and replaced with a metal deck concrete floor, a significant thermal mass upgrade, which carries underfloor heating throughout. The finish is porcelain wood-effect tile across both the ground floor and basement.
The layout was reorganised into three distinct zones: a formal living room at the front, separated when needed by crittall-glazed double doors, a formal dining area in the middle, and the kitchen, island, breakfast area and rear extension at the back, with floor-to-ceiling sliding stacking doors opening directly onto the garden. A new WC was added at entrance level.
The Victorian elements worth keeping were retained. The original hallway tilework, a period feature, was preserved throughout with only spot repairs. The traditional staircase was refurbished in place. The original timber entrance door with sidelights was kept and refurbished rather than replaced.
WHAT HAPPENED ON THE FIRST FLOOR?
The first floor was reconfigured to relocate the master bedroom from the noisy front of the house to the rear, a quieter position overlooking the mature gardens of the terrace. A small adjacent room was absorbed into a master suite incorporating a substantial en suite with walk-in shower and twin basins, and a bay window seat with built-in storage. The former front master bedroom became a guest suite with direct access to its own shower room.
WHAT SERVICES AND FABRIC UPGRADES WERE INCLUDED?
The project included a full mechanical and electrical overhaul: mechanical heat recovery ventilation (MVHR) throughout, underfloor heating across the basement and the entire ground floor, a whole-house residential sprinkler system, and a new plant room in the basement, sized to house all three systems: the sprinkler header, the MVHR unit and the underfloor heating manifolds.
The ground floor structural deck was replaced entirely, with the timber joists and floorboards taken out and metal deck concrete put in, to provide the thermal mass and flat substrate the underfloor heating requires. Insulation was upgraded throughout.
WHAT DOES STUDIO: MASS CHARGE FOR A PROJECT LIKE THIS?
Here's the retightened section reflecting that correction:
What does Studio MASS charge for a project like this?
Studio MASS's fee for the design and technical delivery at Drakefield Road was approximately £12,500 plus VAT.
That covered a defined scope: full measured survey, complete Building Regulations and technical package, design of the kitchen extension, coordination of fire strategy with a fire engineer, and the tender process and appointment of the Phase 2 contractor. Site monitoring and contract administration through the build were arranged and charged separately.
This is a fee for a defined scope, not a percentage charge for a full service from planning to completion. It represents roughly 1.6% of the £750,000 construction cost for the design and delivery phase.
WHAT WOULD YOU DO DIFFERENTLY?
Studio MASS was appointed mid-construction, which created avoidable pressure throughout Phase 1. Building Regulations drawings had to be produced and submitted while the structural works were already underway, so the team had to survey and draw what had been built rather than designing ahead of it. The basement contractor had started under a Building Notice, a lighter-touch route, rather than a full Building Regs submission. Closing that gap while the site was live added real coordination complexity, particularly around the sprinkler first fix on the ground floor, which had to be sequenced urgently with multiple other trades.
The clear lesson is to be appointed ahead of construction, with a complete technical package and Building Regulations submission in place before a contractor breaks ground. This removes the pressure entirely. Planning permission is not the same as permission to build. The gap between the two is where projects lose control, and where the cost of catching up is paid in time, stress and a compressed programme.
THE OUTCOME
The house is now a genuine long-term family home across four levels. The basement is in daily use: gym in the mornings, cinema and games space in the evenings, and the radiologist's office during the day. The ground floor is the heart of the house, with the kitchen, dining and garden flowing together, and formal rooms available when needed. The children have the loft to themselves: two bedrooms, a family bathroom at the mid-landing, and a study room. The first floor master suite faces the rear garden, quiet, private, and overlooking mature planting.
Before, this was a Victorian terrace that felt too small and disjointed for a growing family. After, it is a four-floor home that works at every level, with a full additional floor of living space created below ground.
Drakefield Road demonstrates how a mid-construction rescue, handled by an architectural technologist, can align a build with Building Regulations without disrupting the client's programme or design intent.
Studio MASS is an architectural technology practice based in London. This project was delivered by an architectural technologist, a specialist in technical building design and construction delivery, not a registered architect. All client details have been anonymised. The location is published as Tooting, South West London