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Cumulative settlement

The cumulative settlement of a reinstatement is the level difference, Q, between the adjacent surfaces and the original surface of the reinstatement – see Figure S2.6. This measurement will include the thickness of any materials added during any preceding remedial work.
Figure S2.6 Cumulative settlement
If the cumulative settlement of a reinstatement exceeds the limits shown in Table S2.4 at any time within the guarantee period, an agreed engineering investigation must be carried out jointly with the authority. The investigation should establish whether settlement is likely to continue and determine the extent of remedial action required.
Table S2.4 Structural integrity

Reinstatement width (mm)

Intervention limit Q

Normal ground conditions

Bad ground conditions

Up to 1000

1.5% U or 30 mm
whichever is greater

2.5% U or 30 mm
whichever is greater

Over 1000

1.5% U or 35 mm
whichever is greater

2.5% U or 35 mm
whichever is greater

Where it is necessary to re-excavate a reinstatement to carry out an engineering investigation, the subsequent permanent reinstatement is deemed to be new and the guarantee period begins again.
Where very deep excavation work is carried out in bad ground, consideration should be given to an agreed extension of the interim reinstatement period. An appropriate extension will allow the reinstatement and surrounding ground to achieve an acceptable degree of stability before permanent reinstatement is required. The performance requirements of S2 apply throughout the extended interim period.