Four post-tensioned flat slab development projects are briefly described. To develop simplified methods for predicting long-term deflections, overall deflections and changes in strain within a slab are being monitored for one and a half bays of a typical 9 x 9 m bay structure from construction to one year after occupation. Changes of use over a building's lifetime may require the cutting of holes in slabs. A full-scale test using a specimen of 13 x 21 m containing two 9 x 9 m bays is in progress. Deflections are being monitored under various applied loads, and on completion of this exercise, holes of increasingly larger size will be cut in the slab until two holes large enough for staircases have been created. Over 300 strain gauges are being used to monitor stress. Specifications are being created for grouting procedures for the ducts containing the tendons on completion of stressing. The Concrete Society's Technical Report 43 Post-Tensioned Concrete Floors - Design Handbook is being updated with guidance based on EN 1992-1-1 Eurocode 2. 5 refs.