New Extension Subsiding in Cork City

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The Building Research Establishment states that ground is the greatest hazard to any building, despite the fact that it is not always paid the degree of respect it deserves. For any significant building, sufficient investigation is required to determine if a ‘standard’ approach to foundation construction can be adopted or if a more specialist approach is required.

Some clients are not willing to pay for appropriate ground investigation as they cannot see the value in it. This may be more common where clients opt out of the statutory certification for one off properties or larger extensions.

One of the major risks with poor ground investigation is foundation problems post-construction and this is the case at this property in Cork City. Ground investigation was completed by someone who clearly didn’t have a clue what they were at.

Substruck was subsequently employed to provide data in relation to the ground conditions. Two number dynamic probes were completed in the area of distress and two number close to the original property, known as controls, where no distress was evident.

The results were clear. The probes along the area of distress identified soils of negligible bearing capacity. The hammer dropped under ‘self-weight’ for a distance of 400mm at both locations at depths of between 1 and 2. 5metres – this indicates very soft soils with bearing capacity of less than 10Kn/m2!!! The remaining blow counts were 1 over 100mm and 200mm until refusal was encountered at 3-3.5m!!!! In fact, it was one of the worst set of results that we have seen in quite some time.

In this instance, a piling solution would have been recommended. Unfortunately though, for all stakeholders, this is too late.