... of accuracy required in setting out buildings is covered by BS5606: 1990 Accuracy in Building. Levelling is the establishment of a level height plane for the site from which measurements can be taken. This will be referenced from a datum known as a benchmark (BM), ideally linked to an OBM or a TBM. Steel framed and pre-cast buildings have particular requirements for high accuracy in setting out as the limited tolerances available during the construction stages with much of the dimensional constraint applied off-site. In masonry built buildings a degree more tolerance is available due to the smaller components being assembled. Setting out usually follows a set procedure albeit that most projects provide for a degree of uniqueness that requires skill and forethought to be applied before setting out proceeds. A typical approach would include: 1.) An appraisal of the setting out documents to obtain the fundamental setting out data and this would include ...

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