Substructure

The Building Cost Information Service (BCIS), Elemental Standard Form of Cost Analysis Principles, Instructions, Elements and Definitions 4th (NRM) Edition published by the Royal Institution of Chartered Surveyors (RICS) in 2012, describes the rules for preparing an elemental cost analysis in standard BCIS format.

It defines the term substructure as:

‘All work below underside of screed or, where no screed exists, to underside of lowest floor finishes including damp-proof membrane, together with relevant excavations and foundations (includes walls to basements designed as retaining walls).’

It suggests that the function of the substructure is to, ‘… transfer the load of the building to the ground and to isolate it horizontally from the ground.’

According to BCIS, the substructure includes:

• Foundations up to and including the damp proof course.
• Lowest floor assembly below the underside of the screed or the lowest floor finish.
• Basement excavation.
• Basement retaining walls up to and including the damp proof course.

This a fairly narrower definition which excludes items such as; finishes, basement walls not in contact with earthwork, retaining walls not providing external walls, and so on.

Some much broader definitions consider the substructure to include all works below ground level, although clearly, this is a fairly ambiguous description.

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