Abstract: An expansion joint for building panels, such as concrete floor slabs, comprises a U-shaped drape of a flexible, fire-resistant, impermeable material such as stainless steel foil. The opposite legs of the U-shaped drape are fastened between respective adjacent slabs and a mat of expandable fire-resistant material inserted within the U-shaped drape between the slabs. The impermeability and flexibility of the drape, coupled with the insulating property of the mat provide an inexpensive, effective fire seal between building panels that can also accommodate seismic displacement.