Download Refurbishment of concrete buildings: The decision to refurbish

GUIDANCE NOTE GN 7/99
REFURBISHMENT OF CONCRETE
BUILDINGS:
The decision to refurbish
A J Martin, BSRIA, C A Gold, BCA
INTRODUCTION
It is estimated that currently 8 million m2 of office space requires refurbishment, much of it constructed in the
1960s and 70s in reinforced concrete. These buildings have the potential to provide the standards of
accommodation required in the 21st century if refurbished in the correct manner. There are many factors
influencing the refurbishment of concrete buildings and this Guide presents the main issues from an
owner/occupier or developer’s viewpoint, together with cost summaries and illustrative case studies. The Guide
also provides useful contextual information for structural and building services engineers and architects.
The emphasis is on concrete-framed buildings that are typically used for offices. However, much of the
information is also common to other building types such as housing, hospitals, schools, retail premises and
hotels as well as to the growing number of buildings undergoing conversion such as, redundant office buildings
being converted to residential, retail or hotel use, for example.
This is the first of three publications concerned with refurbishment. The second document covers the detailed
technical aspects of structural and services refurbishment [1], whilst the third considers approaches for the
design of new buildings so that they will be more adaptable to future changes in requirements[2]. These two
documents are intended for consulting structural and building services engineers and architects.
CONCRETE BUILDINGS - A VALUABLE ASSET
Concrete buildings dating from the 1970s and
earlier, offer several benefits compared with their
more recently constructed counterparts. These
benefits are:
♦ the buildings are often in a favourable location
♦ the buildings are higher and have a larger
footprint and more car parking than would be
allowed under current planning regulations
♦ narrower floor plates and natural ventilation are
often found in these buildings, thus meeting the
requirement of an increasing number of clients
for opening windows (occupants are more
tolerant of poorer internal environments if they
have greater control over the environment in their
space)
♦ mechanical cooling can be added where
required
♦ there is a shortage of large buildings, and this
may add value to the refurbishment.
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Factors influencing rental income
♦
♦
♦
♦
♦
♦
♦
location
building image
building condition
flexibility of layout (column grid)
internal environment
internal appearance
extent of car parking
♦ proximity to transport links.
The refurbishment market is larger than the new build
market and possession of refurbished concrete
buildings can form viable economic stock. If a
building is part of a portfolio it may be possible to
remove it from the rental market for say, eighteen
months, refurbish it and then put it back on the
market with the increased rental income repaying the
investment within five to ten years, depending on the
factors given in the box above.
Refurbishment of concrete buildings - The decision to refurbish
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Approximately 10% of office space is refurbished in
some form every year[3] and the internal
environment in terms of thermal comfort achieved
and ambiance created can be indiscernible from
that found in a new building.
There is much less prejudice against concrete
buildings than there used to be. Whilst problems
with concrete buildings can exist, such as high
alumina cement (HAC), and corrosion of
reinforcement (see Refurbishment of concrete
buildings: Structural and services options)[1], these
problems are well known and consultants have much
experience in overcoming them. There are many
examples of successfully refurbished concrete
buildings, as illustrated in the case studies at the
end of this guide.
There are a number of improvements that can be
made to concrete buildings, including:
♦
♦
♦
♦
♦
adding solar shading
reducing floor loadings by removing floor screed
adding lift shafts, risers, and escalators
improving ventilation and air conditioning
extending floor plates, perhaps adding 20% to
net lettable area
♦ adding additional floors.
"Refurbishment of concrete buildings is
not just bread and butter work - there are
some very interesting things that you
can do with them"
Nick McMahon.
THE IDEAL OFFICE BUILDING
♦
In order to decide whether to refurbish or demolish
a building it is worthwhile considering what is
required from an office. The ideal building has to
satisfy many requirements. It must be in the
correct location to express corporate image as well
as providing adequate transport links for the
workforce. It must provide a comfortable internal
environment and be flexible in layout to allow for
future organisational changes. From the owner’s
viewpoint it must maximise rental income or
building asset value.
Location is the principal factor and city centres
remain favourite for offices, despite the downsizing
and re-organisation of businesses in the 1980s and
early 1990s that led to many relocations to out-oftown developments. Such relocations were
encouraged by the availability of car parking and
the avoidance of congestion. Out-of-town
developments have recently been limited through a
combination of factors including:
♦ recent stringent planning restrictions
♦ Government encouragement for regeneration of
urban centres through re-use of brownfield sites
♦ expected Government measures to reduce the
use of private transport and car parking spaces.
These are further reinforcing town and city centres
as the first choice for companies when relocating.
In a recent survey on behalf of The Royal Institution
of Chartered Surveyors (RICS)[3], availability of car
parking, flexibility of floor plates for fit out, the
indoor working environment and
proximity to transport links were cited as the top
four criteria affecting tenants' choice of office
properties. When selecting office space,
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Refurbishment of concrete buildings - The decision to refurbish
businesses require flexible space that can respond
to organisational changes and business
developments. The growing importance of the need
to optimise use of business space and the
environmental conditions within it is demonstrated
by the growth of facilities management as a
profession.
Methods of working within offices are also
changing. Work-forces often consist of teams of
workers who come together to complete particular
projects in a horizontal structure rather than the
vertical hierarchy that was previously favoured.
This is reinforced in businesses where downsizing
has resulted in more flexible staff that operate in
well trained, adaptable groups rather than rigid,
departmentalised sections. This style of working
necessitates workspace that can allow for future
changes in layout and usage and particularly
favours column free, open plan spaces with few
cellular offices. It also means that rents can be
increased because more people can be
accommodated per square metre.
The indoor environment is also important and
employers attach great importance to keeping staff
happy, motivated and productive. Environmental
comfort is thus of prime concern, together with the
provision of office space that is clean, modern and
aesthetically pleasing.
When selecting office space, businesses
require flexible space that can respond to
organisational changes and business
developments
Environmental comfort is of prime concern
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A
WHY REFURBISH?
The gross floor area
of a new building on
a brownfield site is
likely to be
significantly less
than the building it
replaces due to
planning restrictions.
Many occupied buildings do not meet the ideal criteria. Whilst some
elements are not changeable, such as location, other aspects can be readily
upgraded to improve working and organisational conditions as well as to
maximise asset/rental income value. However, not all refurbishment work
will be financially viable and every case requires individual assessment.
Nonetheless, it is increasingly found that refurbishments do provide more
than adequate returns on investment (see Levels of refurbishment and costs
on page 4). Table 1 shows characteristics of different building types and
how these can affect refurbishment.
Table 1: Characteristics of different building types
Period
1900 - pre WWII
Advantages
May have high ceiling.
Designed for natural ventilation. Narrow floor plate
aids this. Add solar shading and spot cooling in
high heat gain areas. Heating, power and
communications routed around perimeter.
Late 1950s/1960s
Open plan layout.
Designed for natural ventilation. Narrow floor plate
aids this. Add solar shading and spot cooling in
high heat gain areas. Heating, power and
communications routed around perimeter.
1970s
Larger floor-floor height than 1960s (for services).
Deep plan, a disadvantage due to need for air
conditioning and artifical lighting.
Open plan layout.
Larger floor-floor height. Raised floor for
services.
Open and deep plan layout.
High electrical power capacity.
1980s
The alternative to refurbishment of an existing building
is to demolish it and build a new one. This, however,
is costly in monetary and environmental terms
(through the use of raw materials), as well as in terms
of the extended time period required to obtain planning
permission, demolish and re-build. Further, planning
permission is likely to severely limit replacement
buildings in terms of height; plot ratio, number of
parking spaces allowed, etc. A further benefit of
refurbishment is that it may be possible to phase the
refurbishment so that part of the building remains
occupied, thus generating income. It should also be
remembered that refurbishment is significantly less
time-consuming than demolition and rebuilding,
perhaps taking two thirds of the time. When the cost
of finance and the loss of rental income are taken into
account this represents a significant sum.
The principal reason for refurbishment is to
maximise income or asset value. The survey
carried out on behalf of RICS [3] suggests that a
typical 1960/70s speculative office in a central prime
site that had been comprehensively refurbished both
© BSRIA GN 7/99
Disadvantages
May be listed building (delays due to negotiation
with English Heritage).
Structural partitions - inflexible space, poor
circulation, poor insulation.
Low floor loading (may not accommodate current
loads without strengthening).
Low floor-floor height.
Large glazed areas leading to high heat gain.
Low floor loading (may not accommodate current
loads without strengthening).
Relatively lightweight partitioning.
Poor insulation and high air infiltration rates.
Single glazing.
Addition of raised floor complicated around lifts
and stairwells. Routing ducts and pipework may
be difficult.
Lightweight construction. Possible high air
infiltration through facade, poor insulation. High
heat gain through fully glazed facades.
Lightweight construction. Over-specified
ventilation and air conditioning - difficult to control.
internally and externally could increase the letting
value by 16 - 20%, from £25/ft 2 (£270/m2) to £30/ft 2
(£323/m2). The variation in letting value ranged from
an increase of 6% to an increase of 30%, depending
upon geographic area. Such rental increases easily
offset the loss of rental income during
refurbishment. Table 2 shows the typical costs and
times to recoup the investment for different
refurbishment levels based on the improvements in
rental income obtainable. This is based on previous
surveys[3,4] and consideration of cost breakdowns
given in journal articles on refurbishment.
Further benefits may be obtained from capital
allowances that can potentially be claimed for the
construction or acquisition of building services plant
as well as where alterations are carried out to
facilitate installation of plant. This might include
demolition of a wall or creation of a hole in a slab for
ductwork.
Phased refurbishment can be carried out
whilst the building is still occupied.
Refurbishment of concrete buildings - The decision to refurbish
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Table 2: Levels of refurbishment
Type
Cost £/m 2
Minor/
cosmetic
170 - 400
Approximate
time to carry
out (months)
1-3
Services
200 - 400
3-6
Structural
150 - 400
2-6
Major
500 - 700
2 - 12
Complete
800 - 1500
6 - 18
New build
800 - 1500
18 - 24
Approximate
Description
payback
period (years)
2-5
This will involve re-decorating, improving signage and lighting,
replacing floor coverings, exterior painting and repair, minor
changes to the fittings. Typically takes place at 5-year intervals.
5 - 15
Complete replacement of heating, ventilation and air-conditioning
plant. Associated pipework, ducting, terminal units, controls and
insulation may be replaced or upgraded as necessary. Typically
takes place at 25-year intervals (control systems more frequently).
5 - 15
Addition of new lift shaft, escalators or risers, necessitating
structural alterations.
5 - 15
This will involve major changes to the services and the interior
fittings but without any significant structural alterations. May
include addition of raised floor, improvements to core areas and
entrance halls, new lighting, internal shading. Typically takes
place at 25-year intervals and in conjunction with a lease renewal.
10 - 30
This will involve significant structural alterations, such as
extension of the floors or partial demolition to create an atrium or
stripping of the building back to the concrete frame. New cladding
may be fitted together with the installation of new services and full
fitting out. Timing of a complete refurbishment is variable but likely
to take place in conjunction with a lease renewal.
10 - 30
Construction of a new building, excluding demolition of an existing
building and loss of rent.
The principal issues to be considered to
maximise income or asset value as part of a
refurbishment are:
♦ Aesthetics
♦ Need to upgrade services
♦ Change of use
♦ Change in Regulations
♦ To attract new tenants/retain existing
tenants
♦ To increase net lettable area
Aesthetics
The appearance of a building is particularly
important. A poor exterior or interior appearance
will influence the market perception of the building
and will deter many companies from taking a
tenancy. Refurbishment, possibly only of parts of
the building such as the facade or the entrance and
other public areas, will overcome this.
Need to upgrade services
A poor working environment caused by ineffective
air conditioning, heating or ventilation will require
replacement of, or addition to, existing plant. This
requirement may also be brought about by
increased heat gains in the building, perhaps
demanding the use of air conditioning. The
introduction of air conditioning can also eliminate
unacceptable external noise. Alternatively, cooling
requirements may be reduced in areas where solar
shading and more efficient, modern office
equipment and lighting
are provided. These reduced heat gains may
eliminate the need for air conditioning, thus
reducing capital costs.
4
Refurbishment of concrete buildings - The decision to refurbish
Refurbishment of services will provide the
opportunity for a more energy efficient building with
consequent running cost savings and reduction in
whole life costs. Consideration of whole life costs
is of increasing importance to building owners who
are beginning to be concerned by the operating
costs of their buildings. Building energy usage and
associated cost may be an area that is
significantly affected by future legislation.
Other reasons for building services refurbishment
relate to the upgrading of electrical services and
office communications to meet changing business
needs and the upgrading of other systems such as
lifts or escalators, fire detection, security and
building management to provide greater
functionality.
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Change of use
Many refurbishments are brought about by changes
in organisational requirements. Space needs are
constantly changing as whole companies,
departments, and teams of workers expand and
contract. This leads to internal moves taking
place, at which point the decision is made to
refurbish while the space is clear. Other changes
of use relate to conversion of parts of a building to
other uses, such as storage areas to office space,
or offices to dining areas.
Common changes of
building use
Office to:
Warehouse to: gallery
office
residential
Hotel to:
Complete changes of building use are growing in
number. Over-supply of office space during the
first half of the 1990s left many offices unlettable.
However, many of these buildings can now meet
a market need for residential, hotel and leisure
buildings with the increased rental income or
asset value paying for the conversion. This has
been aided by the regeneration of many urban
areas, making previously undesirable areas
attractive. The survey by RICS [3] states that up to
30% of all redundant office property in UK cities
could be converted to other uses, with over 50%
being suited to residential use, approximately
18% for hotel use and 8% for retail. The survey
also showed that property owners estimated that
approximately 4% of their office space would be
converted to other uses over the next two years.
Change in Regulations
There are many national Regulations and local
Acts that apply to building refurbishment. From the
structural point of view, there may be a requirement
for increased design floor loading. Services-related
regulations include those imposed by the
Workplace (Health, Safety and Welfare)
Regulations, 1992 which applied retrospectively to
all existing buildings from 1996 and required, for
example, lighting, heating and ventilation to meet
minimum prescribed standards.
To increase net lettable area
One way of greatly enhancing the value of a
building is to be able to collect more rent from it.
This can be achieved by increasing the net lettable
floor area. Methods of doing this include building
an extension or adding extra floors, moving service
cores to the outside of the building or extending
floor plates.
♦ improve appearance
♦ improve efficiency
♦ utilise space
© BSRIA GN 7/99
hotel
retail
residential
office
To attract new tenants/retain existing tenants
One of the primary reasons for refurbishment is
to attract new tenants or to retain existing
tenants, particularly when a current lease is
about to expire. In some cases this may be at
intervals of 5 years or less.
Leases arranged after 1992 are on better terms
for tenants, typically with a break clause every 5
years to allow for changing tenant requirements.
In addition, there is currently an excess of office
space in many areas and it may be difficult, or
even impossible, to lease out un-refurbished
property.
In general terms, the owner of a poor standard
building, either from the point of view of its
appearance or its services, can only expect a
low rental. Factors affecting rental income are
given on page 1.
Reasons for refurbishment
♦
♦
♦
♦
♦
♦
to attract a new occupier (97%)
to retain existing tenants/occupiers (90%)
to increase yields (86%)
to accommodate new services (73%)
statutory requirements (44%)
to improve energy efficiency (33%).
Taken from a survey by RICS Refurbishment in
the office sector 1997/8[3]. The figures in
brackets give percent of respondents indicating
factor is 'important' or 'very important' from a
choice of four categories.
♦ meet new regulations
♦ refurbish to attract new tenants
♦ extend to increase lettable area
Refurbishment of concrete buildings - The decision to refurbish
5
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CASE STUDIES
The following case studies illustrate a number of points concerning refurbishment and show the practicality of
reviving 1960s and 1970s buildings. Full accounts are given in Refurbishment of concrete buildings: Structural
and services options [1].
City Point, London, EC2: 36 storey building extends floor area by 20%
♦ 36-storey concrete frame building with ribbed
slabs built in 1964
♦ building stripped to frame
♦ existing screed removed, reducing floor load
by 1 kN/m2, allowing addition of 100 mm
raised floor
♦ extension of floor plates by 1 m allowed
addition of extra floor area
♦ new ducts for services provided by removing
ribs to create the required hole size.
Courtesy of Sheppard Robson International.
1 Neathouse Place, London: Maximisation of lettable space and improvement of the quality of the
office environment
♦ 12-storey concrete framed structure built in
1959
♦ drab facade, no air conditioning and too many
structural walls for a desirable, modern office
building
♦ floor loading minimised by removing 60 mm
screed
♦ floor space maximised by replacing the spine
shear wall with a steel support system
♦ inner staircases removed and new plant
rooms, staircase and toilets added externally
♦ structure re-clad in glass giving dramatic views
from inside the building, good light penetration
and air extraction routes along the perimeter of
the building at every level
♦ air conditioning provided by air treatment
modules located away from the offices to
maximise net lettable area
Photo, courtesy of Palladin Publications
♦ the approximate capital cost for all the work
was £18 million (£135/ft 2 or £1500/m2).
Courtesy of Chesterfield Properties, Avery
Associates, Buro Happold, YRM(E).
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Refurbishment of concrete buildings - The decision to refurbish
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Howard House, Bristol: Conventional office building undergoes services refurbishment to
improve lettable value
♦ 7-storey office building constructed in 1975
with a floor area of 31,000ft 2
♦ in situ concrete frame structure with precast
concrete cladding panels and double glazed
windows
♦ services within the building had reached the
end of their life
♦ capital and running costs of replacing low level
perimeter induction system not justifiable by
rent obtainable
♦ internal environment now controlled using a
combination of natural ventilation via existing
openable windows and a quasi displacement
ventilation system using the existing ductwork
♦ induction units removed, increasing net
lettable floor area by 2,000ft 2 (6.5%)
♦ refurbishment work, including new power and
communications wiring, new heating plant and
distribution system and new fire alarm system,
cost approximately £25/ft 2 (£270/m2).
Courtesy of Dorset County Council Pension Fund,
King Sturge, RSW plc, Sure Foundation Building
Services Ltd and Latter Ramsay Partnership.
Normanby College, Kings College Hospital, London: Extra floor added
♦ Normanby College was constructed during the
early 1970s
♦ steel plate bonding rejected due to technical and
handling difficulties
♦ extra floor added on top of the reinforced concrete
ribbed roof slab
♦ strengthening work took 4 weeks at a cost of
approximately £60,000 (£7/ft 2 or £80/m2).
♦ strengthening with carbon fibre composite strips
doubled the live load capacity of the slab
Courtesy of Kings Healthcare NHS Trust, John Mowlem
Construction plc, Concrete Repairs Ltd, Sika Ltd .
Boots D10 building, Nottingham: 1930s concrete factory partially converted to office
accommodation
♦ fully glazed southern facade led to summer
overheating and winter overcooling
♦ English Heritage required the facade
appearance to be maintained
♦ original single glazing replaced with double
glazing and internal blinds were added in the
office area
♦ floor screed removed to allow addition of raised
floor in office area
♦ services pipework left exposed on ceiling slab
Photo, courtesy of Architects Journal
♦ the approximate cost of the work was
£1500/m2.
Courtesy of AMEC Design and Management and
Boots Ltd.
© BSRIA GN 7/99
Refurbishment of concrete buildings - The decision to refurbish
7
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ACKNOWLEDGEMENTS
This project was carried out jointly by the British Cement Association (BCA) and the Building Services
Research and Information Association (BSRIA) with additional contributions from the Reinforced Concrete
Council (RCC), Dr Tony Jones (formerly BCA), and independent consultant Dr John Clarke. The work was
carried out under the Department of the Environment, Transport and the Regions 'Partners in Technology'
programme DETR Ref 38/13/22 (cc. 1399). The project was managed on behalf of the DETR by FBE
Management Ltd. The steering group comprised representatives from Buro Happold, Monodraught Ltd, Nick
McMahon Ltd, Ridd Wood Partnership and Sure Foundation Building Services Ltd.
Department of the Environment, Transport and the Regions.
DISCLAIMER
All advice or information from the Building Services Research and Information Association and the British
Cement Association is intended for those who will evaluate the significance of its contents and take
responsibility for its use and application. No liability (including that for negligence) for any loss resulting
from such advice or information is accepted.
REFERENCES
1 GOLD C A, MARTIN A J. Refurbishment of concrete buildings: Structural and services options.
Guidance Note GN 8/99. BSRIA 1999. ISBN 0 86022 526 7.
2 GOLD C A, MARTIN A J. Refurbishment of concrete Buildings: Designing now for future re-use.
Guidance Note GN 9/99. BSRIA 1999. ISBN 0 86022 527 5.
3
Refurbishment in the office sector 1997/8. The Connaught Report. The Royal Institution of
Chartered Surveyors. 1997.
4
KENDRICK C, MARTIN A, BOOTH W. Refurbishment of air-conditioned buildings for natural
ventilation. Technical Note TN 8/98. BSRIA 1998. ISBN 0 86022 498 8.
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