Economic and social feasibility in providing vertical extension for single storey terrace houses in Malaysia

Abstract

Terrace houses are operationally defined as a row of connected housing units that share common partition walls with neighbors at both sides. These walls are placed on the property line and stipulate structural support to itself and the adjoining property. At different stages of life, households need to expand their habitable spaces. Housing extension can be done in two ways, horizontally and vertically. In the current scenario in Malaysia, terrace houses have little option to expand horizontally. However, they still have the potential to expand vertically through retrofitting. So far, not much study has been done on vertical extension of terrace housing through retrofit. Even more, retrofit in residences by using modern technologies such as steel I section beam, H section column, precast slab and footings, are not investigated at all. This study aimed to find out a socially acceptable, economically sustainable, structurally sound, and architecturally efficient retrofit method through vertical extension of existing one storey terrace housing in the context of Malaysia. Social data were collected from households living in single storey terrace houses in Johor Bahru to find out their requirements for vertical extension. After that, architectural solutions were provided according to users’ requirement. Thereafter, structural solutions were done that fit within their expected budget. Finally, social validation was also performed to check the social acceptance of the solutions. The social data were obtained from random samples of 73 households living in single storey terrace houses in Johor Bahru, Malaysia. The legislation for vertical extension was studied through literature review, and conforming to that, and through the survey, householders’ required additional spaces were found to be two bedrooms and one bathroom in the expanded upper floor. Through comparative analysis, five typologies were selected for the next step. The structural retrofit design was using Euro Code was conducted on the selected typologies. Keeping the cost below the budget, the best structural solution was chosen. For social validation, the required duration of retrofit works, and the minimum spaces required by the users during construction were asked through the social survey. An effective project schedule was proposed that can allow users to stay in the house with minimum hazard during construction, allowing them not to be forced to be dislocated during retrofit. The study thus came up with an affordable and socially accepted structural retrofit solution that can be applied to all typologies o f single storey terrace houses in case of vertical extension. It can offer a better standard of living especially for the low income group without sacrificing financial loss.