Established University campuses located in Australia’s population centres are finding that land available for expansion and growth is becoming increasingly difficult to acquire as population centres have grown around campuses initially set up on the fringes of these centres.
With adjacent land usually available at a premium, the capital costs for new developments often have to include the costs associated with land purchase, site decontamination and modification or conversion of existing building stock.
An alternative approach is to maximise the potential of existing land owned by the university by carrying out vertical expansion of existing building stock.
There are key issues that need to be considered when assessing conversion or vertical expansion of an existing building. For both options, a staged feasibility study approach, incorporating risk mitigation strategies for both time and cost control is recommended.
Conversion of an existing building
Issues to consider:
- Planning considerations – if the external appearance of the building is unaffected, planning constraints are unlikely to be an issue, although any change of use has to be consistent with the local zoning laws.
- Age of the Structure – the older a building is, the closer it potentially is to the end of its design life.
- Form of Construction – older buildings incorporate load bearing masonry walls, whilst newer buildings use frames of concrete and/or steel. This form of construction will impact of the viability of internal re-planning of new spaces.
- History of Past Renovations – buildings which have undergone numerous stages of renovations can be inflexible to further modification, particularly in the original building form has been significantly altered.
- Original Intended Design Use – some buildings may have been originally intended for residential use and consequently not be designed for the higher loads mandated for commercial or institutional uses.
- Compliance with the current Building Code of Australia – design actions on structures resulting from earthquake and wind loads have progressively been increased over the last 50 years. Altering too much of a building may invoke the statutory requirement to bring the existing building to full compliance with all existing Australian standards.
In terms of structural possibilities for converting existing buildings, there is a variety of solutions, each with its own advantages and disadvantages.
Increasing the load capacity of the existing building can be achieved by:
- Carbon fibre wrapping existing columns
- Adding steel joists and bearers to floors
- Adding compression ties to vertical elements to increase resistance to lateral loads
- Post-installed masonry reinforcement
- Ground improvement using pressure injection
- If existing documentation is available, refined analysis of the structure and founding material may unlock potential existing capacity.
Minimising structural demolition and construction works can help to avoid triggering a regulatory code compliance update.
Strategic use of existing loading capacity is also helpful – for example having heavy rooms (lecture theatres) located over columns and beams, and light rooms (toilets) located mid-span between columns.
Key recommendations for a stage feasibility study approach are:
- Prior to purchase, undertake a due diligence condition assessment of the existing building infrastructure to identify the form of the existing structure and the cost for any rectifications that may be required as a minimum.
- Try and obtain any or all existing documentation. This information is worth its weight in gold! Document searches at local council offices can uncover valuable data.
- Research the building’s past. If it has already had many different uses, it may have been modified one too many times.
- Look for office buildings and warehouses first, as they have a design load capacity similar or close to educational facility requirements.
The Melbourne Oral Health Training and Education Centre, for the University of Melbourne, for example, saw the major upgrade and refurbishment of an existing building into a technologically advanced facility. The existing building was actually three separate buildings varying in age, which had been previously modified and combined, including the incorporation of what was originally a separate external standalone substation into an undercroft car park.
Whilst limited documentation was available, extensive site survey of the existing structure was carried out to enable detailed new services reticulation to be coordinated with the existing structure, with three different existing beam grid layouts.
This coordination exercise included the upgrade of building power supply, natural gas supply, telecommunications and IT infrastructure. It has also required the integration of new and very specific systems including wet and dry vacuum, a dental compressed air system, a dental gas sedation system, X-ray units, electronic simulator units, a high purity filtered water system, body protection electrical systems and special colour rendition lighting systems.
Vertical expansion of an existing building
Issues to consider:
- It will be unlikely that existing columns have been designed for a significant vertical extension. A preliminary assessment of the extent and therefore the possible ways that the columns could be economically strengthened needs to be carried out first.
- Similarly, it is unlikely that the existing footings have been designed to accommodate a significant vertical extension. However, an assessment of the original geotechnical report and possible additional advice from a geotechnical engineer may provide an increased allowable bearing pressure to be used for design today, and can result in a minimisation of strengthening works required for the footings, thus keeping costs down.
- An increase in the height of the building will require an assessment of the lateral load resistance system for the building. These lateral loads are either wind loads or earthquake loads. An assessment of the existing lateral stability elements (stair and lift shafts, as well as concrete moment resisting frames) needs to be carried out to assess what additional lateral stability elements may be required (for example, additional shear walls.)
- Design for earthquake loadings is more severe now than when the building was originally designed and built. Checks need to be made to establish whether earthquake loads are more or less significant than the increased wind loads.
When it comes to the building’s services, there are three main areas to consider:
- Existing substations currently servicing the chosen building may inhibit the potential to develop the site. Discussions with the relevant building authorities must determine the possible options, and indicative costs to upgrade or relocate the substation.
- A vertical transportation strategy will need to be carried out to determine the required lift configuration for any vertical expansion. This study will also feed into the structural analysis for lateral stability.
- A study of the existing services infrastructure needs to be carried out to identify opportunities and constraints associated with the existing conditions.
A successful vertical expansion approach has recently completed for Swinburne University, which incorporates an additional 850 square metres of floor area above an existing single-storey high portal frame structure.
The existing building was previously used as a soil testing facility and occupied most of the available land area with the exception of a small courtyard to the north. The university wanted to reassign the use of the building as a Film and Television facility.
Due to the limited land area and the boundary restrictions, this could only be achievable by extending the structure up. A tight budget meant complete demolition and a total new build was not viable. As a result, the structural challenge for this project was to cater for the additional floors by re-utilising the existing structure as much as possible.
The age and type of construction of the existing structure meant that the ability of the existing building components to carry additional loads was very limited.
The structural solution selected revolves around the provision of an independent support system for the additional two levels of floor inside the existing building. This strategy enabled the existing building to be used as a shell whereby the existing steel portal frames are ‘stretched’ up to the required height to house the new floors. New vertical steel trusses are used to provide the lateral stability of the overall building.
The result is a structure within an existing structure where most of the original building components are utilised and integrated into a new structural system.