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Core reinstatement and bonding


Suitability of extracted core for re-use

  1. If the core is damaged, it cannot be re-used and the opening must be reinstated in accordance with S6.2, S6.3 and S6.4 or S6.5, as appropriate.
  2. A core is unacceptable for permanent reinstatement where any of the following conditions exist:
    1. It contains any vertical open cracks ≥3 mm wide when measured on the face of the core; or
    2. Horizontal delamination is present in any layer in the core; or
    3. The core is less than 100 mm deep.
  3. If there is any doubt over the integrity of the core, core re-use is not permitted and it must be reinstated in accordance with S6.2, S6.3 and S6.4 or S6.5, whichever are applicable.

Reinstatement of removed large diameter core

  1. Large diameter cores must be prepared in accordance with the Product Acceptance Scheme of the bonding agent, orientated to their original alignment, and bonded in-situ.
  2. The procedure for reinstatement must be included in the method statement for the works which must be available if requested by the authority.
  3. The core must be reinstated so that it is as flush as possible with the surrounding surfaces. The construction tolerance at the edges of the reinstatement is 5 mm maximum at any time within the guarantee period.
  4. Intervention is required if this tolerance is exceeded or there is any significant visual deterioration in the surface of the core compared with the surrounding surface.


  1. A record containing the location and details of all large diameter cores must be registered within the relevant street works notice or permit.
  2. Each core must be registered as an individual reinstatement within the works. For example, for a 600 mm diameter core, reinstatement measures (as registered on the street works notice or permit) should record a measure of 0.6 m x 0.6 m per core extracted. Where two 600 mm cores overlap by, say, 150 mm, the reinstatement should be registered as 0.6 m x 1.05 m (where 1.05 = 2 x 0.6 minus 0.15).
  3. There should also be a comment recorded in the works description area of the notice/permit, for example, “Large diameter core hole(s) outside No 1 High Street”.