The land use planning system plays a central role in promoting housing affordability in many cities of the United Kingdom, Ireland, North America and the Netherlands, by ensuring that the planned supply of new housing matches demand. The planning system also plays an important role in preserving existing dwellings and creating new housing that is affordable for low- and moderate-income earners. Planning approaches for affordability and new affordable housing creation can be grouped under five key strategic objectives: increasing housing supply; reducing barriers to affordable housing development; preserving and offsetting the loss of low-cost housing; encouraging new affordable housing; and seeking a dedicated affordable housing supply in new developments. Different planning mechanisms will be effective in delivering these outcomes in different market contexts. For example, in high growth areas, protective mechanisms may be required to retain existing levels of low-cost housing, whereas in areas of lower land value non-financial incentives could be introduced that encourage a proportion of the development to be set aside for purchase by social housing providers or low-income households.