Acronym for 'Inverted Box Rib'. The profile was first manufactured in the USA in 1914 and in Britain under American patent in 1918 for use as a walling and vertical cladding material. It was originally imported into South Africa in the 1950s. A local engineer, Thom Warren realised the water-carrying potential of the material and patented the IBR profile as a roofing material. It was first used in this fashion on the wardens quarters of Leeukop Prison. The architect GRAFF came up with the innovation of covering the troughs with a lay-on ceramic tile, called 'Britti Tiles,' this both for aesthetic reasons as well as to circumvent bey-laws where the use of galvanised sheetmetal as roofing material was prohibited this in itself a 'snob-value' restriction to meet the sensibilities of 'up-market' neighbourhoods!