Studio Anne Holtrop | Carlos Gonzlez Lobo | Kengo Kuma | BC Architects & Studies | EVR Architecten | Rebecca Horn | Mir Architectes | Ltjens Padmanabhan | Lukas FsterVirtually all architects have worked on a home extension at some point in their career. Increasing the size of a property is perceived as a sign of success of having room to store more things, and to buy even more and a materialisation of social aspiration.But in the climate emergency, extensions also help toincrease a buildings useful life. For a co-operative apartment block in Zrich, additional balcony space has made room for solar panels, while Jamie Gatty Irving suggests the maligned British conservatory could be part of a decarbonisation revolution. Yet extensions are only truly sustainable if they are built with biosourced, local materials and if they contribute to social justice. InBrussels, for example, materials are reused and recycled to transform police barracks into a new urban block, while in Paris, social housing units are inserted within and atop an old workshop, vertically extended with a timber frame and hempcrete.In large parts of the world, homes are built and gradually extended by residents themselves. Sometimes an architect might have a hand in the initial efforts as Carlos Gonzlez Lobo did in the aftermath of Mexico Citys 1985 earthquake. But whether planned or not, extensions persist, and crop up as residents lives change. As Nancy Kwak observes in the keynote essay, this kind of self-help activity isthe most important way in which cities have grown in thelast 80 years.1518: Extensionscover (above) photograph by Tako RobakidzeFollowing the collapse of the USSR in 1991, centralised planning and housing provision stalled in cities like Tbilisi, Georgia. In its absence, inhabitants have taken matters into their own hands, constructing self-built often precarious extensions, nicknamed kamikaze loggiasfolio (lead image)William Blakes 1793 engraving presaged the death throes of the capitalist growth paradigm, in which the desire always for more has prompted plans to colonise the MoonkeynoteCore demandsNancy KwakbuildingEl Agujero de Vysoka cultural centre in Asuncin, Paraguay by Lukas Fster, Nicols Berger, Sergio Ybarra, Guido Martnez, Javier Rodrguez, the Escuela Taller and studentsLaurence BlairbuildingSiyadi Pearl Museum in Muharraq, Bahrain, by Studio Anne HoltropSuha HasanrevisitExtendable post-earthquake housing in Mexico City, Mexico by Carlos Gonzlez LoboMichael Snydercity portraitBarcelonaJulia Capomaggi and Llus OrtegaoutrageDonald Trumps Arctic expansionsKirsty VolzbuildingCentro de Arte Moderna extension in Lisbon, Portugal by Kengo Kuma and AssociatesEdwin HeathcotebuildingUsquare Feder university buildings in Brussels, Belgium by BC Architects & Studies, EVR Architecten and Callebaut ArchitectenChristophe Van GerrewayreputationsRebecca HornJana BaumannessayA short history of the conservatoryJamie Gatty IrvingbuildingSocial housing vertical extension in Paris, France by Mir ArchitectesJustinien TribillonbuildingBalcony extensions and communal garden room in Zrich, Switzerland by Ltjens PadmanabhanEleanor BeaumontessayOffshore gridGke Gnel