The requirements regarding robustness given in BS8110 are ‘deemed to satisfy’ the 1985 Building Regulations. An important addition to the BS8110 requirements regarding robustness from its predecessor is the stipulation that, in structures of more than four storeys, ‘key elements’, whose failure would cause the collapse of more than a limited area close to the member concerned, should be identified. The inclusion of specific requirements regarding structural stability marked yet another change of attitude between the appearance of the original version of CP114 in 1965 and that of CP110 in 1972. All structures of any height must be provided with effective horizontal ties, both peripherally and internally. Since the internal ties must be effectively uninterrupted throughout their length, the laps employed between the successive lengths of bar provided to meet stability requirements must be sufficient to cater for the full characteristic strength of the bar.