Feasibility Study for 5 flats and a garden dwelling in Lewisham
The project at a glance
Project type
New build flats feasibility study Lewisham | Small residential development | Site intensification
Location
Westdown Road, Lewisham, London
Brief
Feasibility study for the demolition of an unsafe existing house and redevelopment of the site to create a replacement residential building containing flats, together with a separate self-contained dwelling within the rear garden.
Development potential tested
A replacement main building with 5 flats, together with a single-storey 2-bedroom garden dwelling, creating 6 residential units in total and 5 additional homes beyond the original single dwelling.
Architectural services provided
Feasibility study, pre-application design proposals, planning submission and Building Regulations considerations, and preparation of proposals to request pre-application advice from Lewisham Council.
For related regional project evidence and homeowner advice, see our South London residential architecture page.
Feasibility study for a structurally failed house on a planning-sensitive deep plot
GOAStudio was appointed to test a replacement development strategy for a structurally failed Victorian house on a deep residential plot in Lewisham.
The study considered whether the site could support a new main building with flats together with a separate rear garden dwelling, while maintaining a credible planning position on a site affected by a non-designated heritage issue.
The existing house was in a severe state of disrepair and structurally unfeasible to repair.
The rear garden extended to approximately 30 metres, creating scope for a more intensive site strategy than a straightforward replacement dwelling.
Site context
The site is on the southern side of Westdown Road and includes a front garden and a rear garden of approximately 30 metres in depth. It sits within a predominantly residential area and is within walking distance of Catford and Catford Bridge stations. The site is not in a conservation area, is not listed, and is not adjacent to a listed building.
The planning position was relatively open in those respects, but the site was still sensitive.
The existing house was considered to have architectural merit and was treated as a non-designated heritage asset. Any redevelopment strategy therefore had to address not only density and layout, but also the planning case for demolition and replacement.
Existing condition
The existing building was an attractive Victorian house, but one in a severe state of disrepair. The brief records major structural failure arising from long-term subsidence caused by clay soil movement.
Vegetation had grown into the building fabric, including the roof, resulting in further damage to walls, floors and roof areas. The house was considered unsafe for occupation and structurally unfeasible to repair or retrofit.
That condition was central to the feasibility position. The redevelopment case depended on demonstrating that the site could not reasonably be taken forward through retention and upgrade, and that replacement development was the more realistic route.
Development brief
The brief for this new build flats feasibility study Lewisham was to test how far the site could be taken as a small residential development and whether the rear portion of the plot could support an additional dwelling alongside a replacement main building.
The main points under review were:
• replacement of the unsafe existing house
• intensification of the site through a new main building containing flats
• a separate self-contained dwelling within the rear garden
• likely planning and Building Regulations implications
• whether the site could support a viable development route beyond concept stage
The feasibility work also considered likely development value and build cost at an early stage, so that the design options could be tested against a realistic commercial framework.
Development option tested
The feasibility study explored a redevelopment strategy consisting of:
• a three-storey replacement main building
• and a self-contained single-storey dwelling within the rear garden
The main building followed the front building line and stepped at the rear in a way that related to the footprint of the existing house and the neighbouring properties. The rear garden house was positioned lower within the plot and handled as a quieter landscape-led element in order to manage visual impact, overlooking and privacy.
This tested a more intensive use of the site shaped around frontage, plot depth, side access, neighbouring gardens and the architectural character of Westdown Road.
Access and practical feasibility
Access to the rear dwelling was to be taken through the side gap characteristic of the Westdown Road streetscape. The proposals retained this side route and used it to create a sloping stepped access of approximately 20 metres from the street to the rear house. The brief also notes that further consultation would be required in relation to emergency and fire access.
The main building was arranged with level access at entry level, shared circulation, and access to refuse and cycle storage both via the communal entrance and directly from the external side path. The overall scheme was conceived as a car-free development, supported by the site’s public transport connections.
These practical points were part of the feasibility study from the outset. Access, servicing and fire strategy were not treated as secondary matters to be resolved later.
Application to similar sites
This feasibility study is relevant to sites where:
• the existing building has failed structurally and replacement development is under consideration
• the plot depth creates scope for intensification beyond a straightforward replacement house
• the planning position is relatively open but still sensitive because of local character or non-designated heritage issues
• density, mix, landscape and access all need to be tested together at feasibility stage
• development value needs to be considered alongside planning and design logic
This project is a useful reference for deep residential plots where the planning case depends on combining demolition justification, intensification, access, landscape and housing mix into one coherent strategy.
Accommodation mix
The feasibility study tested a mix of homes intended to make efficient use of the site while remaining realistic in planning and market terms.
Garden dwelling
• 2-bedroom, 4-person single-storey home
• 70 sqm
• separate access
• large south-facing private garden amenity area
Main building
Ground floor
• Flat 01: 3-bedroom, 6-person family unit
• 95 sqm
• private south-facing garden amenity area
• communal entrance, bin store and bike store
First floor
• Flat 02: 2-bedroom, 3-person flat
• Flat 03: 2-bedroom, 3-person flat
• 61 sqm each
Second floor
• Flat 04: 1-bedroom, 2-person flat
• Flat 05: 1-bedroom, 2-person flat
• 50 sqm each
The study replaced one obsolete dwelling with a more usable mix of family accommodation, smaller flats and a separate rear-garden house. The brief notes that the proposals were intended to reflect local demand and likely buyer demographics.
Sustainability and Passive House ambition
The site’s south-facing orientation was treated as an opportunity to achieve a high level of environmental performance, and the brief records sustainability as a central consideration throughout the design stage.
The proposals were developed with a Passive House ambition, including:
• generous openings for daylight and cross-ventilation
• high levels of insulation
• airtight construction with heat recovery ventilation
• triple glazing
• LED lighting and smart controls
• rainwater collection and sustainable drainage
• solar photovoltaic and solar water heating potential
• and possible use of ground source heat pumps linked to the excavation works and partially sunken garden house
The brief also states that the project was intended to be developed further with the support of a Certified Passive House Designer or Consultant, with the aim of moving towards Passive House certification at a later stage.
Design and planning response
The design development was guided by two requirements: increasing density and maintaining a credible relationship with the character of the street. The brief describes this as a balance between maximising occupancy and density and retaining the architecturally significant character of the immediate area.
Westdown Road is characterised by Victorian housing, generous front gardens, yellow stock brickwork, stone detailing and a clear rhythm of roof forms and spacing. The replacement main building was therefore developed to sit within that architectural language rather than against it.
The rear garden dwelling took a different approach. It was proposed as a partially sunken single-storey house with vertical charred timber cladding and a green roof, with the roof kept to a low profile at no more than 2.2 metres above adjacent ground level. This allowed the rear unit to remain visually recessive while still making productive use of the garden portion of the site.
Residential quality and landscape
he brief notes that the proposals were developed to provide generous rooms, considered layouts and flexible living arrangements aligned with the London Plan and Lewisham supplementary planning guidance.
The intention was to replace an obsolete residential arrangement with a more relevant mix of homes and a more efficient use of the site.
Landscape was also part of the feasibility logic. The rear garden was treated as an active part of the site strategy rather than residual land. Existing trees were to be removed and replaced with a landscape approach aimed at improving greening, biodiversity and amenity while retaining the broad character of the large gardens in the immediate area.
Explore similar development projects
This new build flats feasibility study Lewisham scheme sits within GOAStudio’s wider experience of small residential developments, feasibility studies, site intensification and planning-led design for developers.
See our property development architectural services page for more on how we support developers, landowners and small urban schemes across London.
You can also explore related case studies including:
Looking at a similar site?
If you are assessing a large garden plot, a failing existing building, or a site with scope for replacement development and added density, early architectural advice can help establish a realistic basis for the next stage.
We provide architectural services for residential projects in the following London Boroughs:
Barnet, Camden, Enfield, Hackney, Hammersmith and Fulham, Haringey, Islington, Kensington and Chelsea, Lambeth, Lewisham, Newham, Tower Hamlets, Waltham Forest, Wandsworth, Westminster
We specialise in
- Greener homes
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