12 How House Building is Changing and Why More Homes Through Manufacture A Housing Forum Working Group Report scheme in Barking and Dagenham. Laing O’Rourke has ploughed millions into developing its prefabrication factory near Worksop, which is currently developing DfMA prototypes that utilise more lightweight modular steel frames and a range of alternative cladding options3 . Elsewhere, procurement organisation http://www.constructionmanager.co.uk/news/laingorourke-ramp-offsitesolution-housing-crisis/ ( http://www.insidehousing. co.uk/sectors-first-housebuilding-factory-movesstep-closer/7008182. article?adfesuccess=1 http://www.insidehousing. 3 July 2014) 4 Procure Plus is planning to create the first offsite factory dedicated to social housing, which could see up to 1,000 homes produced in the North West of England each year from 2016. According to a report in Inside Housing magazine4 , Procure Plus has engaged (February 2015) 5 co.uk/development/sociallandlords-increase-use-ofoffsite-methods/7008558. article ( March 2015) consultants to assess the viability of developing the pre-fabrication assembly plant, which would cost £2-3 million to construct, to produce homes for the 40 local The different types of offsite manufacture — Offsite manufacture is a catch-all term to describe technology where a component or a significant proportion of a house is built away from the site – usually in a factory. From the outside, homes built using these techniques may not look any different to traditional homes, as they may still be clad in a brick ‘slips’. Volumetric: These units are 3D modules assembled in a factory. The term ‘modular’ or ‘pods’ is used to describe load-bearing units. The main market for volumetric is for closed modules. One of the main advantages is that these can be whole rooms that come fully plumbed and wired which are transported to site and stacked on top of each other on ready laid foundations, to form the building. This method is popular for highly standardised accommodation such as hotels, student residential halls and care homes and flats in urban medium and high rise situations. Mar City is a developer which uses steel framed volumetric units which are fully kitted out with kitchens and bathrooms and transported to site. The modular units or pods may just be bathrooms. With pods the big advantage is that services installation is transferred into factory engineered conditions. For example, more than 30 trade activities are transferred off-site when bathroom pods are used. This leads to fewer people on site, easier commissioning and less rework. Panellised: Increasingly popular in the construction of housing is the use of panellised systems. These systems involve the on-site assembly of flat panel walls to form the internal load bearing element, and cassette floors (again a floor panel) and roofs. Systems range in complexity from simple timber or light steel panels (open), or concrete panels and cassettes, to more complex factory-finished units incorporating insulation, lining, doors, windows and services distribution (closed panels). Closed panel construction is the logical step up from standard open timber frame manufacturing, as the insulation, plaster board and electrical systems are installed offsite within the panels before delivery to site allowing the unit to be wind and watertight in one day. A major innovation in recent years, which is increasingly being used, is structural insulated panel systems (SIPS), where the rigid insulation core is bonded to sheet linings to form the panel. Cross-laminated timber (CLT) is also starting to make its mark. CLT panels normally form the structural floor and wall element of buildings, and have been used successfully to build up to nine storeys in the UK. It is typically used in offsite manufactured panels delivered to site for erection via crane. Cross-laminated is formed in a similar fashion to the more familiar gluelaminated timber beams (‘glulam’), using small sections of timber bonded together with permanent adhesives with the grain perpendicular, resulting in structural strength across two dimensions, and improving structural integrity and dimensional stability. As well as aiding speed of construction panellised systems offer flexibility in terms of layout and room size. The integration of Building Information Modelling in the production of systems, including those supplied by Fusion Building Systems, has enabled a degree of mass customisation to be achieved at relatively low volumes – giving housebuilders greater flexibility. Fusion Building Systems Business Development Manager, Stewart Hackney, told The Housing Forum that lightweight gauge steel has been gaining in popularity because it does not settle or shrink and provides a better thermal and acoustic performance. Housing can be constructed from hybrids of modular and panellised systems. The Housing Forum’s view is that it is essential to ensure that appropriate technology is chosen for appropriate sites. housing associations that form its client base in the North West. The magazine reported that the project is being monitored by the Homes and Communities Agency, which wants to increase offsite construction as part of its 2015-2018 affordable homes programme. Inside Housing also published a survey in March 2015 which found that 15 out of 17 major housing associations intended to increase their use of offsite construction, including timber frame and modular builds5 . The 17 associations together have a development pipeline of 22,544 homes over the next three years, for which 57 percent will utilise “offsite techniques”. Most of the associations cited advantages in terms of cost, build quality, speed of delivery, fewer weather delays, improved energy-in-use and smaller carbon footprints.
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