3-flats are common in certain older neighborhoods. Four Plus One: an apartment building consisting of four stories above a parking lot. The four floors containing the apartment units are of wood-frame and masonry construction. It was particularly popular in Chicago during the 1960s and 1970s, especially on the city's north side. Garage-apartment: an apartment over a garage; if the garage is attached, the apartment will have a separate entrance from the main house. Garlow: a portmanteau word "garage" + "bungalow"; similar to a garage-apartment, but with the apartment and garage at the same level. Garden apartment: a building style usually characterized by two-story, semi-detached buildings, each floor being a separate apartment. Garden flat: a flat which is at garden (ground) level in a multilevel house or apartment building, especially in the case of Georgian and Victorian terraced housing which has been sub-divided into separate dwellings. Housing cooperative (or Co-op): a form of ownership in which a non-profit corporation owns the entire apartment building or development and residents own shares in the corporation that correspond to their apartment and a percentage of common areas. In Australia this corresponds with a "company title" apartment. Loft or warehouse conversion can be an apartment building wherein part of the unit, usually consisting of the bedroom(s) and/or a second bedroom level bath is sub-divided vertically within the structurally tall bay between the structural floors of a former factory or warehouse building. The lofts created in such are locally supported by columns and bearing walls and not part of the overall original load bearing structure. Maisonette: an apartment / flat on two levels with internal stairs, or which has its own entrance at street level. Mess: a building or flat with single bedroom per tenant and shared facilities like toilets and kitchens. These are popular with students, bachelors or low wage earners in the Indian subcontinent. It is similar to the bedsit in the UK. Some variants include multiple tenants per bedroom and inclusion of a centralized maid service or cooked meals with tenancy. Mother-in-law apartment: small apartment either at the back, in the basement, or on an upper level subdivision of the main house, usually with a separate entrance (also known as a "Granny flat" in the UK, Australia New Zealand and South Africa). If it is a separate structure from the main house, it is called a 'granny cottage' or a 'doddy house'. Such