Cost model: High-rise housing refurbishment

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The government is reappraising the UK’s social housing in order to meet its decent homes target by 2010. Here, Davis Langdon & Everest examines the costs, key issues and associated problems of refurbishing a tower block

Refurbishing tower blocks

Tower blocks have come to symbolise many of the problems of public housing in the UK. Forever associated with the partial collapse of Ronan Point, tower blocks are prone to other problems, including heating issues, water ingress and poor security. Many of these problems can be addressed through refurbishment, although a wider regeneration programme, dealing with tenants, site management and maintenance is needed to turn an estate around.
Tower blocks are well suited to the needs of both young and old people who do not need family accommodation. These groups are growing in number, so refurbishment is vital in bringing existing, underused housing stock back into full use. Government funding, such as in the Estate Regeneration Challenge and the transfer of stock from local authorities to the registered social landlord sector, has been used to address problems in some of the UK’s worst public housing (see overleaf). Refurbishment is increasingly seen as a sustainable option as it achieves high densities. However, social housing has suffered from a shortage of capital investment over many years. The current estimate of backlog maintenance is £20bn and the government has committed itself to bringing all social housing to a “decent” standard by 2010. Although £1.16bn was committed for expenditure between 2003 and 2006, this has to fund new-build work, including 80,000 key worker units, as well as the refurbishment of the existing stock.

Housing estate challenges

Problems experienced on some local authority estates relate to the physical condition of buildings, the facilities provided and the social aspects of living on estates. Increasingly tenants are concerned about management issues – racism, noise, litter and so on. Key issues include:

Matching residents to building types. Neither towers nor medium-rise blocks are suitable for families. Deck access blocks will often be demolished before towers to make way for low-rise family housing.
Security at the building perimeter and at shared facilities such as car parking is essential to attract tenants back.
Upgrading of communal facilities.
Structural issues, which are usually localised. Where substantial problems exist, demolition may be necessary. All refurbishments should include checks that remedial works that followed the Ronan Point disaster have been undertaken, but the focus of work will be on small-scale problems, such as:
Carbonation caused by chemical reactions in the concrete, triggered by the ingress of atmospheric CO2 into porous concrete, resulting in rebar corrosion and concrete spalling. Repairs involve the cutting out and replacement of affected concrete by patch repairs using proprietary repair mortars and in extreme cases replacement of bar reinforcement.
Chloride content – chlorides from sea and road salt, and from additives to speed the curing of concrete, can result in localised but very aggressive corrosion damage to rebar. The remedial techniques include desalination of affected panels and patch repairs.
Delamination of panels can occur in two instances. In insulated concrete panels, the outer leaf may need to be tied back using expanding or chemically fixed bolts to compensate for the inadequate embedment or number of original ties. Second, in concrete frame buildings with brick infill cladding, delamination of the outer bricks can occur where no movement joints were specified. This is not common but is difficult to remedy without recladding.
Non-structural problems include water ingress, typically caused by defective detailing of the joints between panels, or between panels and windows, and defective fire stopping, either in risers, or at junctions between non-load bearing wall panels and floors.
Architectural problems on tower blocks relate to three primary areas; public areas, building performance and remodelling of flats:
Public areas in tower blocks are often too small and of poor quality, encouraging neglect and antisocial behaviour. Physical problems include standards of security, poor sightlines and low ceilings, restricting options for lighting.
Building performance issues include thermal insulation standards, water ingress and condensation, which are dealt with by window replacement and overcladding.
Internal layout of flats – restricted by load bearing structure and affordability. Typical works are: changing flat configurations to provide one- and two-bedroom units; changing room layouts to provide appropriate access to bathrooms, WCs and so on; and providing secure, alternative escape routes and fire doors.
Building services work usually involves replacement of installations within the flats. Problems associated with the landlords’ building services systems are primarily related to replacement of soil stacks, lift replacement and reorganisation of lift entrances.
Tower block refurbishment solutions
In addition to dealing with the physical defects of the building, a tower block refurbishment project has to address wider regeneration objectives, relating to tenant needs and the long-term plans for the management and improvement of the estate.
The key solutions as part of a refurbishment project are as follows:
Dealing with security
Eliminating risks for tenants is crucial. The most important elements are:
Extending the boundary away from the main entrance
Creating foyer areas with better security, sightlines and lighting, perhaps with concierge service
Installation of TV entry phone systems.

Improving flats

Replacing kitchens, bathrooms and services
Enclosing balconies with additional glazing
Minor layout improvements. Bathroom and WC layout and access to be improved – any major changes usually relate to fire escape.

Improving building performance

Repairs to structural defects
Improvements to the building envelope. Poor insulation, water ingress and condensation problems can largely be addressed by improving the performance of the external wall in two ways:
Overcladding using metal or resin-based rainscreen panels is the preferred option, as it is largely maintenance free and can provide a high quality, long-lasting finish. Rainscreen systems are suited to tall towers, where wind loads are higher. However, rainscreen systems can involve a cost premium of £150/m2 over a render finish.
Render finishes involve the covering of the external face of a building with layers of insulation, mesh and wet render. Render has a lower initial cost and can be installed without the detail design of a cladding system. However the substrate has to be carefully prepared to guarantee long-term performance. Render applications, including insulation, typically cost between £ 90/m² and £120/m².
Replacement windows, or the introduction of trickle ventilation to reduce condensation, may also be specified as part of the refurbishment.
Improving building services – usually replacing heating and hot water systems and soil stacks:
Central heating Electric storage heaters have minimal builders work requirements and avoid the dangers of gas use in towers. Local gas-fired systems are operationally efficient but involve more builders work and increased fire risks.
Soil stack replacement often requires the full decant of residents. The works will also include fire stopping between floors.

Improvements to communal areas

Main foyer. The main foyer provides a major opportunity to improve facilities and change the expectations of tenants. The introduction of a new architectural element, providing more space, facilities for community use and improving security meets this objective. New entrance foyers will typically be glazed, to increase visibility and security, and create a public defensible space.
Upper floor lobbies. Typically only used by residents of the flats on that floor, so significant investment cannot be justified. Works tend to be limited to finishes and improved fire compartmentalisation in open lobbies, which rely on natural ventilation.
External works improvements involve increasing parking provision and some hard landscaping features. Perimeter fencing, to provide an additional element of security, may also feature.

Housing transfer

Transfer of the ownership and management from local authorities to the registered social landlords sector or into PFI has been continuing since 1988, and more than 600,000 dwellings have been transferred in 151 schemes, involving £9.8bn of private finance. In the past two years, this rate has accelerated to a maximum of 200,000 units a year in order to meet stock improvement targets and to diversify the management of public housing in the UK.
Local authorities have three options in transferring ownership and management, including the PFI, “arm’s-length” management companies and large-scale voluntary transfers – the most popular option, which involves the transfer of the ownership and management of public sector housing from local authorities to independent, not-for-profit RSLs, which have access to private finance. These deals can only proceed with tenant approval and typically involve substantial refurbishment works. Broader benefits include greater diversity in the provision of social housing, more responsive management, and the potential for greater levels of tenant participation, particularly in estate-by-estate transfers. Critics of LSVTs cite changes in democratic accountability, tenure, the potential for long-term rent increases as problems, and some very high-profile schemes have been rejected by tenants. However, 75% of ballots support transfer – largely because many feel LSVT is the most likely route to getting the funding required to improve tenants’ properties and to turn around problem estates.

Procurement

The refurbishment of tower blocks involves a significant number of challenges, the greatest of which is people. Tenant consultation, security and impact of the works are major considerations, and full liaison by the contractor is vital, particularly if the building remains occupied during works. Issues that need to be addressed include access to flats, liaising on fit-out options, health and safety, and dealing with tenant complaints.
The decision to decant or work around existing tenants will depend on the scope of works to common facilities. Major structural works or soil stack replacement that either require control of tenant behaviour (such as not using toilets and bathrooms) or that will cause major disruption will generally require tenant decanting.
Procurement options are influenced by the Housing Corporation’s pro-Egan policies and also by the need for cost certainty. There is limited opportunity for the use of prefabricated solutions; innovation is more likely to focus on process. Design-and-build continues to be a popular contract for this type of work, and partnering can be developed on estates with multiple towers, deriving benefits related to site set-up, community liaison and greater cost certainty.

Cost breakdown notes

The cost breakdown above is based on the comprehensive refurbishment of a system-built 11 storey tower block with 63 flats. The scope of the works includes the complete replacement of kitchens, bathrooms, heating and electric wiring within the flats, and the recladding of the tower in rainscreen panels and render. Works to communal areas include the replanning of lobbies, upgrading of electrical services and finishes, the replacement of soil and vent pipes, and the construction of a new two-storey lobby.
Rates in the model are current at fourth quarter 2002, based on a competitive lump-sum tender and a location in the North-west. The programme is based on working around tenants rather than a decant. The overall cost is inclusive of external works, preliminaries and contingencies. Professional fees and VAT are excluded.
Rates in the model may need to be adjusted to take account of specification, site conditions, procurement route, programme and location. Details of location factors are given in the table below.