Subsidence Investigation

Subsidence Investigation

In very simple cases, all that is required is a visual inspection that can determine what action is needed to remove the cause of the problem.

Sometimes, the investigation requires more information to be gathered, drainage surveys, ground investigation, geological survey map reviews, checking historic maps and building control/planning records, monitoring cracks and levels. Whatever is appropriate, we have the skill and experience to undertake the necessary investigation and then make recommendations.

We take a measured approach; first we consider the symptoms and their background. If the answer is simple, it is probable repairs can be implemented without delay, but sometimes we will want to consider ground conditions, rate of movement, extent of distortion and cracking and then we will decide what is the appropriate repair.

Many believe site investigations are always required, this is not necessarily the case. Nor is it correct to say that investigations are not necessary to deal with subsidence.

It is however, true to say that investigations are likely to be required if the damage is of such magnitude that foundation work is almost certain to be needed, or if initial repairs or mitigating actions have not resulted in building stability. Investigations would also be undertaken if there is an identified probability that a third party may be responsible for the damage (usually a nearby tree).

Assuming investigations are necessary we would normally seek at a minimum a trial hole to establish the depth and configuration of the foundation and the type of soil the foundation rests in to. The trial hole is typically extended with a window sampler to a minimum depth of 3.0m. We use a specialist investigation company for the ground work and laboratory testing.

Soil tests should at a minimum establish soil type, moisture content, approximate shear strength and atterberg limits (for clays). A common error we see is for a ground investigation to be undertaken without the correct soil tests being carried out. As a result, the wrong conclusions can be drawn and in the case of litigation, the opportunity for a recovery is lost. Without the appropriate information, underpinning cannot be properly designed and indeed, the problem causing the damage may be incorrectly diagnosed.

We will tailor investigations to the requirements of the client and our instructions. We can provide a simple explanation of the factual results of investigations or we can provide suitable technical reports right up to Expert Opinions for use in litigation.