RCKa have embraced Offsite and other MMC on a number of projects, taking time to understand a range of systems which allows them to select the most appropriate for the job in hand. This research-led approach has provided them with the opportunity to employ these systems within projects which are often considered to be unlikely candidates for innovative approaches to building construction. They have also often encountered resistance to the use of new technologies; this is frequently down to a misunderstanding of what pre-fabrication really involves, coupled with concerns about appearance and longevity.
RCKa believes however, that the use of Offsite & MMC offers advantages over traditional construction methods which far outweigh any limitations. Fast construction time and accuracy of assembly are obvious benefits, but in addition, with a good understanding of the system it allows interesting architectural details to be achieved in a much more cost-effective manner compared to traditional methods.
The two examples shown on this page are winning entries for UK housing competitions both planned with Offsite in mind. The first is a design for the City Waterside development in the heart of Stoke-on-Trent. This scheme, involving the construction of some 400 new-build homes in the heart of the city, was designed to achieve Code for Sustainable Homes Level 6. Part of the environmental strategy involved the use of highly-insulated SIP panels providing both structure and envelope. The houses have large openings which look south over the landscape beyond; a clever sectional arrangement affords houses on both sides of the street the same dramatic aspect.
The second scheme is the RCKa winning entry for the Gateway goes for Guild housing competition. Set within a sensitive historic area of Preston, the use of carefully-chosen brick was an integral part of the entry for fourteen homes which responded to the surrounding context. The use of a pre-fabricated, super-insulated timber-framed panel was to help achieve Code of Sustainable Homes Level 4, through the integration of a mini district heating system, utilising an array of standard domestic boilers and solar thermal panels. A future upgrade to Level 5 will therefore be possible with only limited capital investment.
A common mistake in the use of MMC is to try to fit a particular system to a particular building style, resulting in a great deal of wastage and cost. RCKa believe that the use of a particular Offsite system should not lead the design approach; rather it must compliment it.

Run by the RIBA Competitions Office for Community Gateway Association, the competition attracted 74 entries, and the shortlist of four was announced in November last year.

Our winning scheme, comprising 14 new houses on a tight urban site to the north-east of Preston’s city centre, contains a mix of different unit sizes, with an innovative parking solution allowing an unbroken elevation to the southern boundary, and mews houses along a homezone to the north.

Dave Warlow, Community Gateway Association, said:

Throughout the Gateway Goes for Guild competition we have been overwhelmed by the responses and the quality of the submissions sent to us [74 entries].

RCKa have, with their proposal shown a thorough understanding of what we were looking for in this project.

Judges’ comment on RCKa’s proposals

This was a good team presentation from a practice that has relevant experience of housing in the region and a good balance of skills and past track record of working with Registered Social Landlords. The two lead architects both fit the ethos of Community Gateway and the local community and gave a clear indication that they would listen to the local residents and be comfortable working with them. The presentation was very sincere and the team gave the impression that this would be a special project for them.

The panel especially liked the focus on using local consultants and constructors, and the opportunities that the latter would afford for young people in the area to gain apprenticeships and employment. The house plans were well designed and suitable for the BME community, and the team had obviously got a good grasp of the site which was reflected in a well presented analysis. The issue of parking was handled ingeniously by bringing the cars into the garden spaces.

Links:

• Architects’ Journal, 21 January 2010 (subscription required)
• RCKa project page
• Community Gateway Association
• RIBA Competitions Office

This new family home, with two floors of accommodation above a basement plinth, will replace an existing 1930’s timber framed cottage which currently sits on the site.

The basement plinth will be finished in bi-chromatic brickwork which is a feature of local buildings, and the ground and first floors will be clad in a weatherboarding, also reminiscent of other properties in the region.

The house will be manufactured off site, using modern methods of construction to minimise construction waste, reduce construction time and improve thermal efficiency.

The house is design to accommodate three generation of the family. The grandmother, who was born in the existing cottage which the new house replaces, has been provided with a separate wing of the house which is connected back to the main house by a shared entrance lobby.

The pros and cons of different offsite systems – and the applicability of the systems in the bespoke residential sector.

Although prefabrication has been a feature of the UK building industry for many years, there is still a perception that the use of off-site manufacture results in a generic approach to design.

This view is gradually changing as architects are starting to explore the opportunities that Modern Methods of Construction can provide, particularly within the bespoke residential sector. Increased exposure of MMC through the mainstream media is helping to reposition new building technologies within the market, with television programmes such as Channel 4’s Grand Designs recently covering a number of homes built using off-site systems. As a result, consumers are beginning to understand the advantages that this approach can offer.

The key to unlocking the benefits of MMC is understanding the strengths and limitations of the various systems available, and the applicability of each to particular design requirements. It is only through an intimate understanding of each product that it becomes possible to select the most appropriate type for the application. This is particularly important when it comes to designing bespoke homes.

Assessments of the different systems for particular construction projects are usually made on the typical basis of Cost, Quality and Time and most manufacturers have marketed their products by quoting fast construction times, excellent build quality, good thermal performance, value for money and so on. and whilst valid, these attributes should in fact be secondary to the important considerations for a new home.

The general assumption is often that most systems are similar in their application, and as a result design limitations are often overlooked. On a number of occasions we have been approached by clients wishing to build using a particular system which isn’t always appropriate for their specific requirements. It is important to stress that when designing a bespoke home there are more fundamental things to consider, such as ensuring the proposals suit the client and their way of living. It should also be location-specific in order to unlock the full potential of the site, to achieve planning permission and take advantage of the local environmental conditions. Once these parameters have been defined it is only then that we would investigate which system is the most appropriate.

There are generally three categories of off-site system suitable for the bespoke residential sector.

The first is the heavily-branded ‘whole house’ systems which tend to deliver only limited flexibility in their design, whilst achieving very high build quality. In these cases, almost all of the components are manufactured remotely and brought to site for assembly. Design options are usually limited, and bespoke details are usually impossible to achieve. Opportunities for responding to the site are limited as a result. There is a second category of ‘whole house’ systems which offer more flexibility by using a kit of standard details to achieve a bespoke home, either in conjunction with an architect, or using an ‘off-the-shelf’ design. Minor alterations to the standard set of details can usually be achieved, but significant departures can be harder to accommodate.

The systems offering the most design flexibility are those which provide prefabricated structural components, but which are finished on site. This third category includes timber frame houses, SIP systems and others. Here, the primary structure is brought to site to be assembled within a short space of time, and then completed on site with the required internal and external finishes. Whilst this type of off-site construction offers the greatest levels of flexibility and adaptability, quality control and achieving a tight programme are generally more difficult to achieve.

Generally speaking, those systems which offer a high degree of off-site prefabrication tend to deliver less flexibility than systems which combine a level prefabrication with on-site finishing. Much of this has to do with the control that manufacturers require over the various building components. For instance, some offer a choice of window systems whilst others are limited to a standard range – and not always the ones that the architect would ordinarily select.

Another determining factor is often the proximity of the site to the originating factory. Systems which involve a high level of off-site assembly tend to reduce in their capability to adopt bespoke detailing the further they are from the point of manufacture. We have investigated a number of systems originating in mainland Europe which offer a great deal of choice for sites on the continent, but because of logistical issues are able to accommodate less flexibility in the UK where bespoke components cannot easily be flat-packed for transport. With all this in mind, it is impossible to determine which system is the best, but only which is the most appropriate on a case-by-case basis. All offer high levels of environmental performance, enhanced build quality, accelerated construction time and better sustainability credentials over traditional construction methods. The choice will largely depend upon the needs of the brief, and it is this factor which should always lead the choice of system.

Unfortunately there are many bad examples of where MMC have been used to create bespoke houses. Such examples do not take advantage of the potential of MMC and have been built in such a generic style and with so little consideration for design that they would not be out of place on a volume housing estate. The other extreme is that the product chosen is so prescribed that the resulting house does not respond to the needs of the inhabitants or the site, but suits the system perfectly.

We cannot blame the manufacturers for these results and we should be thankful that there are so many different systems to choose from. It is more a question of the product being considered in the right way: people are often not aware of the choice available to them or how far a particular system could be pushed to suit their needs. The ’system’ is not ‘the house’ but one of many potential tools that can be employed to deliver a beautiful, contextual and personal home.

Delivered to site in flat-pack form, the panels are erected within a few days on to a concrete slab – in this case, a beam and block floor. The grey sheeting to the outside of the panels is the breather membrane which forms a waterproof layer on the outside of the OSB boards.

The next stage is to install eco-joists across the structure back to the existing house so that the first floor and roof panels can be installed. Once this has been done, work can begin on the external finishes.

You can view more information about this project here.

The house uses a traditional rural form, but introduces crisp, contemporary detailing, and is clad from locally-produced cedar shingles.

There’s more about this project on our website here.