Examines the current planning issues relating to the construction of mezzanine floors. Mezzanine floor construction is, according to the Town and Country Planning Act 1990 s55(2)(A), deemed to be internal works to a building, not development as defined by s55 of the Act and therefore not in need of planning consent. Local planning authorities, seeking to impose planning conditions on mezzanine construction to prevent occupiers from drastically increasing their floorspace at low cost, have succeeded in a number of cases and have also lobbied for legislative change. Powers under the Planning and Compulsory Purchase Act 2004 s49 when they are enacted may introduce a blanket ban on the introduction of mezzanines without planning permission but more likely a threshold will be introduced above which planning permission for mezzanines would be required. The anticipated proliferation of mezzanine construction before the new conditions are enforced has not materialised. Concludes that the future threshold might not however be the panacea for local authorities' problems created from unregulated mezzanines.