Tre Portar was built by the municipal housing company Stockholmshem in the suburb of Skarpnäck 25 minutes by subway from the City of Stockholm. The project consists of a multi-family housing block of 5 floors comprising 3 staircases and 50 apartments from 2 to 4 rooms. Common spaces are: a restaurant kitchen, dining room, playroom for children, ceramics workshop, exercise room, wood workshop, sauna, guest room and a garden. The residents consist of 1/3 families with children, 1/4 families with teenagers, 1/4 without kids (incl. 5 pensioners). Most are low & middle income people.

The complex is owned and managed by the housing company Stockholmshem, which is owned by the City of Stockholm (run by a board of politicians reflecting the election results). The company has an agreement with the resident association about a certain extent of self-administration. This includes recruitment of new residents, use of common rooms, cleaning of staircases and common spaces. All residents are members of the cohousing association, which annually elects a Board.

The construction of Tre Portar was financed entirely by the housing company. It received no state or municipal support.

The residents are members of a cohousing association which takes care of common spaces and facilities. The residents are divided into cooking teams in charge of cooking according to a revolving scheme. Communal dinners are enjoyed four days a week. Cooking, cleaning and repair is compulsory for members. Residents are also members of working groups and carry out cultural activities together.

The housing project is sustainable in the sense that residents share meals, spaces and equipment. Environment-friendly lifestyles are promoted by collective decisions. The sense of community promoted by common activities can be regarded as an aspect of social sustainability (provided that serious conflicts do not occur).

An apartment of 2 rooms costs Eur 500 a month to rent; while a 4 roomed unit costs Eur 720 a month. This cost includes a share of the common spaces. All apartments have normal kitchens, bathrooms, central heating, refrigerators, freezers, double-glazed windows and high-standard surfacing. The poor households get housing allowances from the City of Stockholm. Tenants have the advantage of not having to pay any installment, but are victims of the Swedish housing policy that denies subsidies to renters while it allows house owners to deduce the interest of their bank loans from their taxes (i.e. the rich are subsidised by the poor).