The last of 593 temporary props will be removed from the British Museum's Great Court roof this week, allowing the steel and glass structure to settle into its final shape and become self supporting. At a slightly premature final de-propping ceremony last week, Buro Happold's Stephen Brown admitted props were still in place at the southern end of the roof as the removal sequence was reassessed to cope with delays in installing the glass roof panels. Recent rain hampered installation, primarily because of the need to apply silicone sealant in the dry. The Great Court roof spans the space between the facade of the museum's rectangular courtyard and the circular reading room, creating the largest covered courtyard in Europe. The fine lattice shell structure consists of about 6,000 individual steel members fabricated by Waagner Biro of Vienna. Removing the props has so far caused the roof to drop by up to 150mm in height and 90mm laterally.