Office retrofit or rebuild? Finding answers to the developer’s dilemma
As the way we work and inhabit workspace changes, a big issue for developers looking to the future of their office portfolios is whether to retrofit or build afresh. Nick Ridout of architects Scott Brownrigg asks the key questions
Retrofitting an office building can mean a wide range of things in terms of intrusion, from a ‘lick of paint’ to stripping it back to the frame, remodelling, re-servicing and extending a building. The level of retrofit will depend on the market conditions, investment models and what product the developer wants to bring to market.
In making decisions, it is important to consider the context. Users are becoming more demanding of their office spaces; leases are becoming shorter and more flexible. The way we work in these spaces has changed dramatically in the last 15 or so years, particularly with the increased emphasis placed on wellbeing and the positive effect it has on productivity and talent retention and attraction. These changing demands are driving a wider range of offers to the commercial office market with an increasing requirement to provide differentiation.
‘Happy to compromise on perceived quality of space…’
Advances in IT and mobility have resulted in a significant rise in start-ups and small companies seeking more affordable office spaces; these occupiers are happy to compromise on perceived quality of space and set up in less fashionable areas, often formerly more industrial spaces. This, coupled with an increasing emphasis on collaboration and exchange of ideas in lieu of more isolated tasks and cellular, hierarchical ways of working has led to the trend in less formal office design.
Standard 25-year leases on 1990s building stock are coming to an end and this is providing redevelopment opportunities. Back then, a higher level of mechanical and electrical servicing was the norm, with associated floor-to-floor heights to accommodate additional air distribution. Floor loadings were designed to accommodate significant quantities of heavy paper and servers. Such a structural capacity is no longer needed to carry the modern-day office and can instead be used as a way of creating additional floor space to make buildings work harder, achieve higher rental values and ultimately become more attractive to potential tenants.
Retrofitting an existing building can have significant benefits as well as some limitations on the final product, so it takes some consideration knowing when to retrofit and when to demolish and re-build. The reality, of course, is that there is no ‘one size fits all’ approach, but below are some of the key issues Scott Brownrigg considers when undertaking a feasibility review, and a brief case study of its project for Aviva Investors at Victoria Gate in Woking.
What is the product?
This will vary upon location, but generally, the expectations on base build offices are shifting. Emphasis on wellbeing, the desire for natural light and greater flexibility means more is demanded of space, and the amenity built into buildings is more varied and demanding on the base build. More volume per user is desirable, so higher ceilings, or exposed services with the structural soffit being the perceived ceiling rather than a suspended ceiling has been the recent trend.
As an aside, we have recently been asked to design a UK scheme for a new-build business park in the Thames Valley with exposed servicing and structural elements where design precedents referenced by the Letting Agents were retrofit schemes. The qualities of space more usually found in retrofit are now making their way into new build schemes, with the line between the two blurring.
When is the optimum time to come to market?
This is obviously very project specific, but there could be advantages to bringing an office building to market at a certain point in time. Depending on the level of retrofit and intervention, there are often significant programme advantages to reusing and adapting the existing structure, which might allow the building to be brought earlier to market, reducing costs and getting quicker returns for the developer.
How far can the existing envelope be extended given planning restrictions?
If there is only the opportunity to add limited additional volume, it is more likely that the existing structure will be able to support this. If working on an existing building that would not be approved under planning regulations, there may be value in significant strengthening and adaptation works to retain this rather than knocking down and rebuilding a smaller volume.
What is the existing floor-to-floor height?
Natural light and an emphasis on volume means that a low floor to ceiling/soffit height is likely to have a detrimental effect on the value or even the ability to let the space. Generally, buildings built from the late 1980s onwards tend to have more contemporary floor-to-floor heights that can accommodate higher ceilings.
What is the loading capacity of the existing structure?
As above, buildings have historically been designed with large floor loading capacity, usually 4 – 5 + 1 kN/m2, with additional loading around cores for server space. As IT and advances in remote digital filing become the norm, we are designing to 3 – 3.5 + 1kN/m2. Floorplates can often be extended outwards as well as upwards utilising the redundant structural capacity in the frame and foundations.
What is the structural grid?
Are the columns at a sensible spacing that does not compromise the space, and can be efficiently used by incoming tenants?
There is significant embodied energy within an existing building. Retaining as much as possible reduces this wastage as well as reducing the transport involved in carting away the old and bringing in the new.
Case Study: Victoria Gate, Woking, UK
Scott Brownrigg originally designed and delivered the original Victoria Gate in 1986 for Norwich Union. The building’s design was pioneering at its time, utilising new techniques in unitised curtain walling and slim efficient construction methods.
Thirty years later, Scott Brownrigg revisited the building to bring it up to 21st century standards for the competitive commercial market. Originally appointed to undertake a simpler interior refurbishment commission, it became apparent during the feasibility stages that exploring options to re-use the existing 1980s structure could bring a more attractive longer-term solution for client AVIVA Investors.
By bringing the original outboard external column structure inside to extend the floor plates beyond the original envelope, infilling the former courtyard and by adding a new fifth floor, a further 25 per cent lettable space was delivered for the client. In addition, a strategy for a total visual rebrand for the 63,375 sq ft building was undertaken to appeal to a speculative tenant. The building is now let to McLaren Automotive.