I know ri-uso is used, and ristrutturazione, too for re-use, but in English here have been attempts to standardize this kind of terminology.
Adeguamento funzionale: "complesso degli interventi condotti per portare/riportare un edificio o sue parti ad un livello di prestazioni funzionali conforme a nuovi o mutati requisiti." ifma.it/index.php?cat_id=13&catname='Glossario' Adaptive Re-use:
"Adaptive Re-use" is used in the architectural world to denote taking an existing structure that was once used for a particular purpose (e.g., a train station), and adapting the architecture to be used for another purpose (e.g., a shopping mall)". http://www.aquinas-multimedia.com/catherine/basilica1.html

See also http://adaptivereuse.net/about-adaptive-reuse/

adaptive re-use + architecture on google gives you over 29,000 hits

The architectural design and adaptive re-use scheme is concentrated etc...

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Note added at 58 mins (2008-06-16 11:38:42 GMT)
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http://en.wikipedia.org/wiki/Adaptive_reuse

If a primary function has changed, (like converting a servants block into a toilet block, or a storeroom into an exhibition hall, a stable yard into car parking, etc ) adaptive re-use is your term. If the building is subject to minor functional adaptation (adding a lift, new fire safety installations, a new bar in an existing cinema, new lighting for an exhibition hall, etc.) to improve existing functionality, what the others say is fine