Urban sprawl may be defined as urban expansion without procedures for efficient land use. It is typically expressed in allocating ample space to roads and parking areas, to buffer zones and leftover spaces between built-up areas, and in residential developments with low densities. Such planning procedures lead to encroachment of valuable agricultural land, to long travel distances, to high infrastructural costs because of long lines of roads, pipes, drainage ditches etc per house, and to a lack of urban qualities. This paper focuses on the role of house types that may accommodate higher densities, especially in large cities of low-income countries. Densities are expressed in floor area ratios, i.e. the ratio between the habitable area on each floor, multiplied with the number of floors, and divided by the land area considered to ‘belong to’ the respective urban type. In many low-income cities both planned and unplanned areas are dominated by detached one-story, one-household units in the middle of large plots, i.e. house types that generate urban sprawl. Among planners and politicians consciousness about the effects of urban sprawl seems to be low, and little is done to promote house and neighbourhood types that allow higher physical densities. Multi-storey buildings require more expensive building materials, construction techniques and the use of skilled labour, which impedes savings through self-help construction, but such obstacles may be partly overcome by applying appropriate technology solutions. Another obstacle is anti-urban attitudes, which may fade away with time. The paper is based on a literature review and on ongoing research on house and neighbourhood types in Dar es Salaam, Kampala, Johannesburg and Cape Town. The paper includes examples of house types that allow higher floor area ratios at the same time as spatial qualities such as cross ventilation, daylight in rooms and proper drainage are safeguarded. It is argued that vertical extensions from one to two-storey buildings may be combined with self-help construction techniques and/or the upgrading of local artisan skills. With new planning procedures floor area ratios in low-income cities may increase from today’s 0.1-0.2 to at least 0.6-0.8, which in turn means either that existing cities may treble or quadruple its population without appropriating virgin land; that overcrowding may be reduced considerably by adding new rooms to each housing unit, or that urban agriculture may be introduced in densifying housing areas without any further expansion of the city.