Maintenance and operating costs in off-site timber framed housing

Increased cost and declining quality have resulted in a growing interest in modern methods of construction (MMC) and, in particular, off-site production. Among Swedish contractors there is currently a specialisation trend towards an increased use of prefabrication and industrialisation in housing construction. The Swedish building regulations was altered in 1995 allowing timber as frame material in multi-storey buildings. Since then approximately 25 000 dwellings have been built using off-site timber framed housing techniques. Still, potential clients and residential property owner organisations are hesitant towards off-site multi-storey timber framed housing and express particular concerns about maintenance and operating costs (together called running costs). Therefore, the manufacturers of timber framed houses in Sweden have engaged in a number of projects which aim at identifying and exploring this uncertainty further. In this paper, maintenance and operating costs in off-site timber framed housing are examined and compared with running costs in traditionally built multi-dwelling buildings with concrete structure as well as average costs of comparable multi-dwellings in Sweden. The factors affecting maintenance and operating costs of residential properties are examined theoretically and empirically. To investigate whether timber frame is an influencing factor on the running costs, data has been collected from Swedish residential property owner organisations comprising economic data, interviews, documents and as well as questionnaires. Cost data on 19 properties, of which 11 are off-site timber framed properties, has been gathered and 16 personal interviews conducted to verify the results. Neither the results from comparative cost data nor interviews nor other documentation display cost differences between timber and other frame materials in housing. The findings should contribute to reduce the uncertainties about long-term costs of off-site timber framed housing.