A piece of garden land can look like an obvious development opportunity. It may have road frontage, established housing on either side and enough apparent space for several new homes. Yet available land is not automatically developable land. The value of a small residential site depends on whether a coherent, policy-compliant and deliverable scheme can be created once access, neighbours, trees, drainage, ecology, character and commercial realities are considered together.
This illustrative feasibility study explains how Hepburn Architects would assess a notional parcel of surplus residential land in Birmingham. It is based on the type of early-stage work undertaken for landowners, homeowners and small developers, and uses the existing hero image from our Residential Masterplan project to show the character of a landscape-led layout. It is not a claim that the specific illustrative site has planning permission, nor is it a substitute for project-specific planning or legal advice.
The example assumes a site of approximately 0.18 hectares, with direct frontage to an established residential street, mature planting along parts of the boundary and neighbouring gardens close to the development area. The landowner wants to know whether residential development is realistic, what capacity might be supportable and how much work should be commissioned before deciding whether to proceed.
The first feasibility question is not ‘How many houses can we fit?’ It is ‘What form of development can this site support well?’
Why feasibility comes before design
It is tempting to begin with house types and a target number of units. That approach can produce an attractive plan quickly, but it often hides the issues most likely to determine whether a scheme succeeds. A narrow entrance may restrict the access solution. A mature tree can influence where a road, dwelling or drainage feature can sit. A neighbouring window may require a greater separation distance. A sewer crossing the land can make an apparently efficient footprint impractical.
A feasibility study puts these questions in the right order. It identifies the planning principle, records the known constraints, tests more than one reasonable response and sets out what still needs to be verified. The result is not a guaranteed planning outcome. It is an informed basis for deciding whether to invest in surveys, consultant reports and a planning application.
For a landowner, that early clarity can prevent money being spent on an overdeveloped layout that must later be redesigned. For a purchaser, it can expose conditions that should influence an offer or option agreement. For a small developer, it creates a more reliable starting point for programme and appraisal.
The illustrative site and client brief
The notional site sits within an established Birmingham residential area. It comprises part of a large garden or surplus land associated with an existing property and is assumed to have potential for an independent access from the public highway. Surrounding development is mainly two-storey family housing, with a varied but recognisable rhythm of front gardens, driveways, pitched roofs and planted boundaries.
At approximately 1,800 square metres, the site appears capable of accommodating more than a single dwelling. However, its modest scale means that every part of the layout must work hard. Space is needed not only for buildings but also for a safe entrance, vehicle movement, pedestrian access, parking, gardens, bin storage, cycle storage, landscape, drainage and the relationships between new and existing homes.
The client’s initial questions are typical:
- Is residential development acceptable in principle?
- How many homes might the site accommodate without appearing cramped?
- Can safe and practical access be achieved?
- How will neighbouring privacy, daylight and outlook be protected?
- Are trees, ecology, drainage or utilities likely to reduce capacity?
- Which surveys and consultants are likely to be required?
- Is there enough evidence to justify progressing to a planning application?
These questions define the work. They also make clear that feasibility is a staged decision rather than a promise that a particular unit count will be approved.
Stage 1: establishing the planning principle
The first desktop review asks whether new housing is likely to be acceptable in this location. Relevant local plan policies, neighbourhood guidance and supplementary planning documents should be read alongside the National Planning Policy Framework. The site’s position within or outside the settlement boundary, any conservation-area status, nearby listed buildings, open-space designations and other policy constraints can all affect the principle of development.
Planning history is equally useful. Decisions on the site, the parent property and nearby plots can reveal how the local authority has approached backland development, garden development, access widths, density, privacy and local character. A previous refusal does not always make development impossible, but its reasons must be understood rather than designed around superficially.
The character of the area matters because a technically possible layout can still be inappropriate. If surrounding streets are defined by detached houses on generous plots, a dense terrace behind existing gardens may feel out of place. Conversely, a compact urban location may support a more efficient arrangement. Density is therefore an outcome of context and design quality, not simply a number applied to the site area.
Hepburn Architects’ Planning Applications service explains how feasibility, planning strategy, drawings and supporting information are coordinated once a viable route has been identified.
Stage 2: reading the site before drawing the layout
A measured topographical survey is normally essential before a planning layout is developed in detail. It should record boundaries, levels, existing buildings, trees, visible services and relevant features beyond the site. Land Registry information is useful, but title plans do not usually provide the dimensional accuracy required for design. Ownership, covenants, rights of way and rights for services should be reviewed by the client’s solicitor.
The site visit then tests what the desktop information cannot show. The architect considers where the land feels open or enclosed, which boundaries are sensitive, how levels change, where neighbouring windows and gardens sit, what the street frontage looks like and whether a new entrance would appear natural. Photographs and observations create a record that can be revisited as options develop.
At this stage, a constraints and opportunities plan can bring the evidence together. Typical constraints include:
- the position and width of a potential vehicular entrance;
- visibility in both directions along the road;
- trees, hedges and root protection areas;
- neighbouring windows, patios and private garden areas;
- changes in level and retaining structures;
- public sewers, easements and utility routes;
- surface-water flow paths and flood-risk information;
- habitat features, protected species potential and priority habitat;
- the outlook and orientation available to future homes.
Opportunities are recorded with the same care. An established planted edge may provide a strong landscape framework. A wider part of the site might form a small shared green. A south- or west-facing aspect can help organise gardens and living spaces. Existing street frontage may allow the development to address the road directly rather than appearing hidden behind it.
Stage 3: access, movement and servicing
Access is often the decisive issue on garden and backland sites. The highway authority will consider visibility, entrance geometry, pedestrian safety, the number of dwellings served and the effect on the existing road. Fire and rescue access, refuse collection, delivery vehicles and the ability for cars to turn may also shape the plan.
A layout should avoid allowing parking and turning space to consume the scheme. Cars need to be accommodated, but the street should still feel like a place where people can walk safely and front doors are easy to find. Carefully positioned parking, overlooked routes and a clear distinction between public, shared and private space can make a compact development feel legible rather than congested.
Servicing requirements are best tested early. Bin stores need realistic collection distances. Cycle storage must be convenient enough to use. Electric vehicle charging, incoming services and meter positions should be allowed for. If an adoptable road is unlikely to be proportionate, the design team should still establish how a private drive will be constructed, drained, lit and maintained.
Stage 4: protecting neighbours and creating good homes
Small residential development is frequently judged through its relationship with existing homes. The design team should map neighbouring windows and distinguish principal habitable-room windows from secondary openings. Separation distances, angles of view, boundary treatments, finished floor levels and the position of private gardens all influence privacy and outlook.
Rules of thumb can help identify risk, but they do not replace design judgement or local guidance. A well-placed blank gable may reduce overlooking, while a poorly positioned first-floor bedroom window can make an otherwise reasonable footprint unacceptable. Changes in level can intensify perceived overlooking and should be shown accurately in sections.
Future residents deserve the same attention. Each home needs useful internal space, daylight, a sensible relationship between rooms, secure private outdoor space and an entrance that addresses the street. Gardens should be shaped so they can actually be used. Leftover wedges beside parking courts rarely create the quality of amenity expected from a new home.
Orientation also matters. A plan that maximises unit numbers but places every living room on a shaded edge may perform poorly. Testing sunlight, outlook and the relationship between kitchens, dining areas and gardens can improve everyday living without necessarily adding floor area.
Stage 5: testing development capacity
Only after the initial evidence has been assembled should the architect test capacity. For this illustrative site, three broad approaches can be compared. They are not presented as fixed proposals; their purpose is to expose trade-offs.
Option A: eight detached homes
A lower-density arrangement of detached houses may reflect the surrounding character and provide clear private gardens. Its weaknesses could include a repetitive access road, inefficient gaps between buildings and a higher land cost per home. Detached form does not automatically create better place quality if the residual landscape is weak.
Option B: ten semi-detached homes
A higher-capacity option may strengthen the appraisal and make more efficient use of infrastructure. It can also place greater pressure on parking, garden depths, turning, tree retention and neighbour relationships. If these pressures result in dominated frontages or compromised homes, the nominal increase in value may not survive the planning process.
Option C: nine homes around shared landscape
The preferred illustrative option sits between the two. A mix of family homes is arranged to define a small landscaped space, with front doors and windows providing natural surveillance. Parking is distributed rather than concentrated in one large court, and the layout leaves room for useful gardens, planting and drainage. The exact dwelling number would remain subject to survey, design development and planning review.
The exercise shows why the highest unit count is not always the strongest development proposition. A slightly lower capacity can create a clearer planning case, reduce abnormal costs and produce homes that are easier to sell or retain. Feasibility should therefore compare quality, risk and deliverability alongside headline numbers.
Stage 6: landscape, trees, ecology and Biodiversity Net Gain
Landscape should structure the layout from the beginning. Mature boundary vegetation can help new development settle into its context, but trees must be assessed by a qualified arboriculturist. Root protection areas, canopy spread, future growth, shading and the space required for construction all need to be understood. Retaining a tree on plan while placing buildings or gardens so close that future pressure for removal is inevitable is not a robust solution.
Ecology is similarly site-specific. An initial ecological review may identify the need for habitat surveys, protected species work or seasonal survey windows. Existing hedges, mature trees, ponds, grassland and nearby designated sites can influence scope and programme. Even where a proposal is exempt from mandatory Biodiversity Net Gain, wildlife legislation and planning policies can still apply.
For applications submitted under the current rules, the site boundary and habitat context should be reviewed carefully. Read our detailed article, Biodiversity Net Gain Rules Changed in August 2026, for the small-site threshold, priority-habitat qualification and practical implications for developers.
The illustrative site is approximately 0.18 hectares, but that figure alone does not prove an exemption. The relevant measurement is the genuine red-line application boundary, and land required for access, visibility, drainage or other works should not be omitted simply to fall below a threshold. The design team should establish a defensible boundary and obtain appropriate ecological advice.
Stage 7: drainage, utilities and ground conditions
Surface-water drainage can reduce development capacity if it is left until the end. The drainage hierarchy, infiltration potential, existing networks, exceedance routes and the space required for sustainable drainage features should be considered while the layout remains flexible. Permeable paving, rain gardens, swales or below-ground attenuation may form part of the strategy, depending on ground conditions and the approving bodies.
A utilities search can identify public sewers, water mains, electricity apparatus and other services that cross or border the land. Their records are not always exact, so further investigation may be necessary. Easements or required diversion works can affect both the arrangement and financial viability.
Historic mapping and environmental searches may also point to contamination, made ground or former uses. A preliminary ground investigation can inform foundations, drainage and abnormal-cost allowances. On a constrained site, discovering poor infiltration or a major sewer after the planning layout is fixed can force substantial redesign.
Stage 8: from spatial capacity to commercial feasibility
An architect’s capacity study supplies critical inputs to a development appraisal, but it is not the appraisal itself. The client and their cost and property advisers should test likely sales or rental values, construction cost, professional fees, finance, tax, planning obligations, infrastructure, abnormal works, contingency and programme.
The layout should be measured honestly. Gross and net site areas, dwelling floor areas, parking numbers and landscape provision need to align with the assumptions used in the financial model. An optimistic unit count that depends on unresolved access or drainage does not provide a sound basis for land valuation.
Sensitivity testing is useful. What happens if one home is removed following planning advice? What if a sewer diversion is required, foundations cost more than expected or ecology delays submission? A viable opportunity should retain enough resilience to absorb reasonable change.
At this point, the landowner can choose whether to pause, seek pre-application advice, commission the remaining surveys or move toward a full application. The important outcome is that the next investment is made with a clear understanding of the evidence still required.
Consultant information likely to be required
The final scope depends on the site and local validation requirements, but a small residential planning application may need coordinated input from several specialists. The feasibility report should distinguish work required immediately from work that can wait until a preferred option has been selected.
- Measured topographical and boundary survey.
- Planning policy and planning-history review.
- Arboricultural survey and impact assessment.
- Preliminary ecological appraisal and any necessary follow-up surveys.
- Highway access and tracking advice.
- Drainage and flood-risk input.
- Utilities search and, where necessary, tracing or trial holes.
- Ground investigation and contamination advice.
- Energy and sustainability strategy.
- Planning consultant, landscape architect or other specialist input where justified.
Commissioning everything on day one is not always proportionate. Equally, deferring a survey that could invalidate the layout creates false economy. The architect’s role includes helping the client sequence information so that the greatest risks are tested at the appropriate time.
A practical route from first review to planning
For a site of this type, a sensible route can be summarised as follows:
- Define the client’s objective, ownership position and commercial assumptions.
- Review planning policy, designations, planning history and readily available environmental information.
- Visit the site and commission an accurate survey.
- Map access, neighbours, levels, trees, ecology, drainage and utilities as constraints and opportunities.
- Test more than one capacity option and record the trade-offs.
- Select a preferred planning-led option rather than simply the maximum unit count.
- Confirm the specialist reports, likely programme and remaining risks.
- Update the development appraisal before progressing to pre-application engagement or a full planning application.
The stages may overlap, and planning officers may not endorse a proposal through pre-application advice. Nevertheless, this sequence gives the client an auditable basis for decisions and helps the wider consultant team work from consistent assumptions.
Key lessons for landowners and small developers
First, do not value land solely by multiplying an assumed number of units by an average sales figure. Capacity should be tested spatially and technically before it becomes a commercial assumption.
Second, establish the genuine site and access boundaries. Land ownership, rights and highway requirements can determine whether an otherwise attractive concept is deliverable.
Third, treat trees, ecology and drainage as design inputs. When they are considered only after the houses have been placed, they are likely to appear as obstacles. When understood early, they can help organise landscape, outlook and identity.
Fourth, protect the quality of the new homes as carefully as neighbour amenity. Planning success and long-term value both depend on creating a good place to live.
Finally, keep the status of the work clear. An illustrative layout is evidence of potential, not a planning consent or valuation. Its purpose is to identify a realistic route, the principal risks and the information needed for the next decision.
Could your garden or land become a development opportunity?
Large gardens, corner plots, vacant parcels, backland sites and underused commercial land can all justify an initial review. Some will support new homes; others will be constrained by access, policy or technical issues. Finding that out early is valuable in either case.
Our Small Residential Developments service covers site appraisal, development-capacity testing, planning-led design and coordinated applications for infill, backland and compact housing opportunities.
Hepburn Architects can begin with a proportionate feasibility review, explain which unknowns matter most and help assemble the right consultant team if the opportunity merits further work. The aim is to replace guesswork with a clear, evidence-led development strategy before significant money is committed.
If you are considering development land in Birmingham, the West Midlands or elsewhere in England, contact Hepburn Architects to discuss the site, your timescale and the decision you need the feasibility study to support.