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If a development is to be successful throughout its build out and provide its stakeholders and financial backers with the expected returns, it must be masterplanned with flexibility in mind.

As large-scale masterplans typically take 10 years or more to be completely built out, the market demand envisaged at the outset is likely to change. The development framework evolving with the masterplan should be able to demonstrate that, within each zone, there is sufficient flexibility to allow more or less space to be built (within the framework parameters) to suit market demand.

An allied factor is the flexibility of use types within the framework. Typically, a mixed-use masterplan being prepared for an outline planning application will be based around a zone plan. Each zone is likely to include two to three use types with a minimum and maximum floor area attached to each one, providing the developer a degree of flexibility, to suit market demand at the time each zone (or phase) is worked up in detail and submitted for detailed planning consent.

For example, a switch from 60% commercial with 40% residential to 40% commercial with 60% residential could be made to suit prevailing market conditions.

Of course, switches of use type must not impair the overall objective of creating a place that works – use types will still need to complement each other and work together in proportions that produce an acceptable financial appraisal.

It is important for flexibility that the public realm is integrated and responds well to more than one use type. At the same time, care needs to be given to avoiding abortive and unnecessary expenditure associated with temporary measures that span across phases – until alternative use types come on stream.

The cost planning framework should be structured to suit this flexible approach.

Grosvenor Estates’ £920m Paradise Project in Liverpool is mixed-use masterplanning on a grand scale – 170,000 m² will be redeveloped by 2008

Switches of use type must not impair the overall objective of creating a place that works

ºÃÉ«ÏÈÉúTV use: future changes of use

Most masterplan schemes will contain existing buildings of one form or another. In some cases, these buildings need to be retained due to their listed status, their blend of architectural styles or for commercial viability.

Although the existing building use may not sit naturally with the mix of uses proposed in the masterplan, a change of use can often be achieved. Conversion of office buildings to hotel and residential uses has been done effectively and delivered functional buildings.

Future trends will require buildings to be flexible enough to accommodate market demands. For example, at some point in the future, a developer may want to convert a multistorey car park into residential accommodation to reflect changing lifestyles. That will demand a flexible design solution that achieves its primary initial function and can allow economical conversion. Deviating from the traditional design benchmark is likely to increase the initial construction cost. A change of use from multistorey car park to residential would need to establish such factors as an optimum size of structural grid, floor to ceiling heights and optimum vertical and horizontal circulation for a potential future use. This forward funding burden would offer benefits in the future when the use was changed.

Using the public realm for different events

Creating a flexible public space with the potential for different uses throughout the year can help define a masterplan scheme for all types of occupiers and other users.

The prevalence of large screens broadcasting England’s World Cup matches in public squares and open spaces is an obvious example of how public spaces can achieve mass appeal and generate income. Restaurants and bars have enabled these functions to be inclusive. Importantly, the amenities adjoining the public realm benefit from the increased footfall.

In order to integrate varying uses of the public realm, design parameters must take into account the likely building use types that a specific area is likely to attract and which are appropriate. For instance, to achieve a realistic and sustainable long-term income stream, the materials used to build and landscape the public realm would have to be durable enough to withstand an increased volume of footfall. Furthermore, the ability to achieve the uncongested flow of people traffic in, out and around the public space will largely determine a user’s appreciation of the space and their desire to return in the future.

Key to establishing a successful and well-received public realm solution is finding the right balance in creating a multi-functional space that is durable, functional, safe and secure. Creating a public realm with a range of continuous active uses will help keep the space alive all year round. It will ensure the space remains vibrant and interactive.

Broadcasting in public squares shows how these spaces can achieve mass appeal and generate income

The potential to achieve a direct income stream from an element of a mixed-use development that would ordinarily not provide one is an obvious commercial advantage, and one that sits neatly with the concept of creating high-quality public spaces, particularly in a city or town-centre location.

Westfield’s £1.5bn White City development is retail-led, but also includes a West London Line train station at Shepherds Bush

Infrastructure: key triggers

The level of infrastructure investment necessary to create a viable mixed-use masterplan development is often one of the most critical factors in achieving a commercially viable solution that minimises forward funding.

Infrastructure investment has certain thresholds whereby a jump to a higher level of capacity, supply, scope or size will be required for the development to function. Flexibility in infrastructure needs to be appropriate to the development’s phasing strategy, which, in turn, will minimise forward funding, bring elements of development on line when required and avoid abortive costs.

The completion of buildings within the scheme will trigger the need to deliver elements of a Section 106 agreement, some of which may be linked to infrastructure works. These works will therefore need to be factored into financial appraisals to ensure a balance of income streams is aligned to control the debt burden and to keep forward funding expenditure within acceptable parameters.

Public transport upgrades can range from the relocation and provision of additional bus stops and the creation of cycle paths to creating new railway stations and tram routes. Although the need to enhance the existing public transport network will largely depend on the likely increase in potential users, the existing capacity of the local network must obviously be taken into account. It is in these instances that significant jumps may need to be made to ensure the increase in capacity is delivered.

Enhancement of major public transport infrastructure, such as new bus and rail stations, can be a complex process involving numerous stakeholders and high up-front capital costs. However, the long-term benefits to the local community can be enormous.

Proximity of the development to major roads and highways can offer a huge draw to potential users. In some circumstances, it may be necessary to form new junctions or trunk roads to serve these highways. Traffic impact studies will determine the extent of this and the most appropriate course of action.

Achieving a sustainable masterplan stretches beyond on-site energy generation

Utility services distribution and capacity within the masterplan boundary can, to a certain extent, be zoned to reduce initial expenditure outlay. Further issues may lie outside the boundary of the masterplan site, if the local network capacity needs to be increased above its current capability. The cost and time associated with these works can be significant.

Sustainability: flexibility to embrace new technology

Developing a design, development and phasing framework that enables both established and emerging technologies is a growing challenge.

If a sustainable masterplan solution is to be reached, financial viability must be balanced with the need to improve environmental considerations and energy generation.

Any successful sustainable agenda will reduce energy demand, increase the amount of energy generated from renewable sources, reduce waste and foster a culture of recycling. This agenda must take maximum advantage of the local resources pertinent to a particular development and be flexible enough to enable the inclusion of emerging and developing technologies in the future. An environmental impact assessment of a large mixed-use development will make it possible to establish where efforts can be best focused.

Sustainable, on-site renewable energy generation was little used until as recently as 10 years ago, but today, photovoltaics, grey water recycling, ground source heat pumps, wind turbines, combined heat and power and bio-mass boilers are all common considerations during the masterplanning process. Combined heat and power generation is particularly suited to mixed-use developments, because their constant day and night time demand can make this approach efficient. Delivering a flexible sustainable framework for on-site energy generation that satisfies current and future demands depends on a balance of generation that is in keeping with the demands of different occupiers and user groups and offers a level of reliability and resilience.

Achieving a sustainable masterplan stretches beyond on-site energy generation. Delivering a solution that reduces the impact of the development beyond the site can offer tangible benefits. Carbon neutrality, compulsory recycling and drainage outflow reduction will all have a major impact on the local environment.

Sustainable urban drainage systems offer the ability to attenuate rainfall before it is released from the site, so reducing the impact heavy rainfall can have on the disposal capacity of the drainage infrastructure. The cost of drainage infrastructure to buildings and all hard landscaped areas across a masterplan can be significant. To reduce this financial outlay without jeopardising drainage performance, balancing ponds could be introduced as part of the landscaping design to accept peak water levels. Introduction of an element of landscaping that can operate as a functional feature of the urban realm can provide a double benefit.

Masterplan schemes present an opportunity to implement far-reaching sustainable approaches that would not be feasible on smaller or individual building projects, although they need to remain flexible enough to incorporate new technologies in future years as the scheme is built out.