2 case studies - rgu

LINK Project – Final Report

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2 Case StudiesIt is apparent from the available technologies and the literature that this project should be driven by the emerging issues, rather than by a need to include every available technology and/or material in the study. By concentrating on studies and projects where the potential benefits of innovative technologies can be realised by the client, routes to overcoming resistance will be uncovered.

Those specific issues that can, and should, be addressed through the study of prefabrication/ standardisation are as follows.

scale of construction number of units labour need continuity of employment potential difficulties anticipated market quality control energy efficiency flexibility at design stage flexibility in use durabilitycost and time of construction planning constraints

The case studies presented in this initial part of the study fall under three categories:

Urban study Peri-urban study Rural location Yorkon Stewart Milne Group Deveci Architects Volumetric Amphion Consortium Webster Associates RB Farquhar Wilcon Homes Celcon

The case studies presented here are designed to highlight a variety of these issues and provided a test-bed for the early development of ideas in consultation with others. It is from a consideration of these case studies that the classifications used in later parts of the project evolved.


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2.1 Urban

2.1.1 Yorkon/Peabody Trust DescriptionA delegate from the project team met with representatives at Yorkon. That visit provided details of manufacturing process, anticipated market, marketing strategy and cost concerns. That information fed into the project and provided useful data for later stages.

The most prominent example associated with this case study concerns a development of flats at Murray Grove, Hackney, North London. The accommodation units were largely prefabricated, and transported to site ready for craning into position. The external cladding panels (timber and terracotta), also prefabricated, were fixed in-situ.

Technology The Yorkon product was used to great effect within the Murray Grove Development.

It is notable that a great deal of political and financial support was required to enable the project’s viability. Yorkon are currently involved with the Peabody Trust on a further project concerning social housing and the application of modular products. A major reason for this continued association was the ability to control operations on site, thus ensuring that potential time benefits were realised.

Costs for the Murray Grove project appeared reasonable (Bagenholm et al., 2001iii), it is expected that economies of scale would appear, should the methods be widely adopted.


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Rationale for incorporation in study The following would be key areas for study, should this be selected for analysis in later project phases.

scale of construction labour need potential difficulties in site management anticipated market - both public and private sector quality control flexibility at design stage flexibility in use - to be addressed cost and time of construction planning constraints - relationship between Client, manufacturer and planning Authority proved vital to project success.

Yorkon and the Peabody Trust are continuing to work together in current and future projects, and the Steering Group may wish to consider the alternative or additional incorporation of other similar projects.


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2.1.2 Volumetric A2. Volumetric DescriptionThe typical Volumetric product is a room “module”, of approximate size 8 by 4 by 2.5 metres high. The product has been used to great effect within the Peabody Trust “CASPAR” project in Leeds.

The modules are typically transported to site ready for lifting into position. The implications of this when dealing with larger distances are recognised, though, and the option for transporting “flat” products is available. The arguable disadvantage of transporting entire units, and thus failing to maximise the haulage potential in terms of weight and eventual living space can be balanced against benefits in construction time, risk aversion and quality control.

Technology: This case study really encompasses 2 previous projects from Volumetric. Both are included so as to illustrate how an essentially static and “standard” modular product can be used in such a way that concerns over aesthetic and living space can be overcome.

ImagesTypical modular flatted development Module being positioned Estate under construction

Typical final appearance

[Note brickwork in-situ outer leaf]


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CASPAR images Image shows volumetric modules being lifted into position.

Design drawings

Typical modular section is shown in bold. Note that the left (inner) part of each flat has been constructed using (prefabricated) wall panels. A comparison with “Posthouse” contruction is shown on the right.


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Preliminary cost appraisal

It is proposed that the modular approach would be of great relevance and value to a study concerning urban-flatted developments. Incorporation of the volumetric technologies in this project would provide scope for the assessment of how the following might influence final costs.

development time initial construction costs finance costs life cycle - durability, maintenance, etc.

To date, two CASPAR projects have been completed, with the costs exceeding normally expected public sector targets by between 10 and 20%. Returns on investment through renting, balanced against running costs, have met project- specific targets for yield. It can be argued nevertheless that long term potential could have been better realised through greater attention to detail at the construction stage.

Clearly, the time taken to move from the design stages to practical completion and occupation will influence both construction and finance costs. Therefore, although certain costs will be effectively fixed (e.g. cost per module), other significant costs will vary according to progress on site.


standardisationmodular construction speed of construction sustainable materials flexible use of materials and technology prefabricated wall panels response to planning constraints design quality post-occupancy evaluation

The value of these projects to the LINK activity is centred on the ready availability of information concerning difficulties of using modular construction within a non-standard plan form. Difficulties concerning management of this project have been reasonably well documented to date, and could be further explored via both the manufacturer and client. If the LINK project is arguing that difficulties of technology, social design, cost and planning need to be overcome to facilitate the success of new technologies, then this may be a good starting point.


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2.1.3 RB Farquhar DescriptionRB Farquhar has developed a strong reputation for the production of accommodation “modules”. These have been widely applied within the design and construction of hotels, and the production of offshore accommodation modules for the oil industry.

The company has two divisions, namely housing and modular production. To date, there has been little practical work completed using the modular products within housing, and this project may provide an opportunity to explore a number of technical, financial and logistical issues.Technology At present, the RBF products have been divided fairly clearly between a housing division, and a modular construction division.

The company has voiced an interest in exploiting the obvious potential benefits of realising potential benefits of collaboration between the divisions, though, and this project may offer an ideal opportunity for us to explore issues of practicality, technology and market influence.

It has been noted that the modules, as constructed at present, allow for great speed of construction once on site, but allow very low tolerances for errors in positioning. This in itself could lead to longer term issues concerning flexibility in use, as difficulties may be encountered where an occupant wished to alter the positioning of fittings.

This issue, although not regarded as critical within the company’s main markets, may be of greater importance within housing. It is intended that the cost, perceptual and technical issues relating to this will be tested later in the project.


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standardisationmodular construction speed of construction sustainable materials flexible use of materials and technology prefabricated wall panels response to planning constraints design quality logistics of transferring technologies between various types of design brief project development and management

RB Farquhar has intimated that the 2 divisions have grown and developed as separate entities. As both have now reached a stage of relative maturity, and clear markets have developed as a result, the time may be ripe to exploit the strengths of each as a collective activity.


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2.2 Peri-Urban

2.2.1 Stewart Milne DescriptionWith a very well established range of mass-market timber frame housing. The company plan to expand the extent to which their houses are prefabricated, and have recently embarked on a project to move a greater proportion of their work into a factory environment.

Images


standardisationsustainable material energy use prefabricated timber frame design flexibility established market recognised need to further optimise the product manufacturers interest in further prefabrication

The Group currently has a development plan for construction of the major elements, and is interested in issues including plan flexibility, use of the roof space, energy efficiency and market placement. The potential benefits in terms of reduced construction time are explicitly recognised by the company. This case study offers the project an opportunity to consider benchmarking strategies and to better understand the balance between technical excellence and market perception.


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2.2.2 Amphion Consortium DescriptionThe Amphion Consortium has worked with a range of groups, and in particular has produced a number of important projects with Beazer Homes (now partnerships first). Beazer have stated a commitment towards greater levels of prefabrication in the future, and have moved significantly towards this through the adoption of large scale prefabricated wall panels.

Images

Rationale for incorporation in study As stated, it is intended that the approaches taken to both variations in the cladding, and the use of wall panels, be incorporated in later stages.


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2.2.3 Wilcon Homes2

DescriptionA delegation from the project team visited Wilcon Homes following the inaugural Technical Forum. Wilcon have recently begun to move major aspects of their construction process off-site, and as such provide an excellent opportunity for us to test the logistical and financial requirements. In addition, Wilcon build using timber frame systems, in a marketplace where timber is not the dominant material. This in itself also offers interesting possibilities for the consideration of marketing, perception and cost.

Sectional elevation

Typical floor plans


standardisationsustainable material energy use prefabricated wall panels design flexibility

2 The information contained here is based on data collected in June 2000


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2.2.4 Celcon DescriptionThe system illustrated, “Jamera”, has to date only been applied within mainland Europe, although the longer-term plan is to offer it within the UK. The system works around the use of large scale aerated concrete blocks, which allow for increases in the speed of construction, over “traditional” concrete systems. There would appear, however, to be a certain reluctance to move towards ever greater levels of prefabrication. For example, the roof construction is very rapid due to the use of longer blocks. Were it possible to mirror this approach in the walls, even greater time savings might be possible. The project would also interested in considering how the large amount of in-situ finishing work (e.g. plaster and rendering) could be reduced.

ImagesConstruction process

Sectional perspective drawing


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standardisationsustainable materials energy use prefabricated wall panels design flexibility


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2.3 Rural

2.3.1 G. Deveci Architects – Proposed dwelling at Balnaguard, Perth Description

Detached 3-bedroomed house on 1.5 stories. Structural post and beam construction, concrete pad foundations (14Nr).Slated roof, with Scottish larch cladding. Exposed rafter ends, with roof draining to cast iron rainwater goods. Inhabited roofspace. Energy system supplemented by 4Nr solar panels.Double-glazed redwood windows, including 14Nr Velux rooflights.

ImagesElevations

Plans


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Sections

Rationale for incorporation in study The following would be key areas for study, should this be selected for analysis in later project phases. This particular design embodies a number of important issues for cost, and potentially important for value.

standardisationsustainable material energy use prefabricated wall panels design flexibility The post and beam construction method.Prefabricated external wall panels Final cladding attached off-site.Panels fixed onto, rather than between, timber posts. Speed of construction Use of Velux windows Energy costs in use Use of local materials and skills Arguably reduced embodied energy (less foundations due to lower weight)


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2.3.2 Webster Architects DescriptionOriginally proposed as office accommodation, the designs are based around the use of large-scale pre-formed steel beams. These interlock in the horizontal plane to form both the roof structure and the cladding.

ImagesElevations

Rationale for incorporation in study This design option addresses a similar issue to that raised by the project in relation to the Celcon designs. That is, could the large-scale prefabrication/ standardisation of the roof construction be used somehow to reduce over construction time. The design could conceivably be used in connection with early outputs from the previous RGU “Affordable Rural Housing” study, where it was proposed that modular rooms be enclosed within a larger frame. That study eventually abandoned that approach due to the high cost of suggested glazing. The approach suggested here, however, may go some way towards addressing this point.

The obvious issues this design raises in relation to aesthetics, social representation and market acceptability present interesting points for investigation.

2 case studies - rgu

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