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Subsidence / Structural Movement / Settlement:Introduction:Welcome to Jim Canning & Partners Ltd. We are a firm of Consulting Engineers offering advice on construction related issues ranging from new builds to existing structures. With offices in Dublin and Cork we offer a nationwide service. Our main area of expertise is focused on the issues of Subsidence, Settlement and Structural Movement in existing structures, and the specification of the necessary remedial works required to arrest this movement. Structural Movement Due Erosion:The slides below show what is one of the most common causes of foundation movement. The first slide shows a leaking drain allowing water to escape into the sub-soil along the side wall of the house. This often has the effect of weakening the sub-soil. The following slides show some of the ways that are often employed to correct the damage caused to the structure.
Subsidence:The term Subsidence has unfortunately become a byword for any structural movement that has it's genesis in a failure at foundation level or below. Technically this is not an accurate description or definition of subsidence. However in the interest of simplicity, and as this page is not intended for Engineers or construction professionals but instead is aimed at people who are concerned that their property has begun to move and are attempting to become more informed about the issues they are facing, we will allow the above inaccuracy to go unchecked here."Subsidence" generally occurs in a structure when the ground bearing the structure yields, under the load of the structure, and compresses to such an extent that the structure settles at the point of failure or compression of the sub-soil. The most common cause of this is demonstrated above whereby leaking drains allow water to enter the subsoil, causing the subsoil to soften. The problem of Subsidence, and in particular house subsidence, is very common in Cork. Cracking:This settlement at the foundation line generally gives rise to tensile stresses in the masonry of the structure, which generally cause diagonal cracking in the walls of the building. These diagonal cracks generally occur at weak points such as window and door opes, and at high level where the rotation in the structure has given rise to the greatest distortion. Horizontal cracks may also occur where the tensile stress caused by the downward movement of the foundations cause the blockwork to separate along the horizontal joint.Most Common Cause:As we have mentioned already, very often the cause of the sub-soil compressing is erosion of the soil due to movement of water, often due to defective sewers or water mains leaking water. This erosion decreases the bearing capacity of the soil by washing away fines in the soil that would have contributed to the cohesion of the soil leaving the sub-soil less dense and in a weakened state, with the result that the house sinks slightly into the weakened subsoil. This type of erosion is particularly common in the greater Cork area due mainly to the make up of the overburden and the Limestone bedrock in the area. The water which has escaped from the drains will not only erode the soil by washing away fines, but may also lead to the solution of sections of the underlying Limestone bedrock.Underpinning:To arrest this subsidence it is generally necessary to underpin the house. The type of underpinning required will depend on the type of soil present and the existing foundations, and should only be specified by a suitably qualified engineer.Insurance:Most building insurance policies will cover subsidence, and again most will cover damage due to an escape of water, which is very often the cause of structural movement. A simple hydrostatic test carried out on the sewers will determine if they are leaking. Digging a trial hole exposing the soil at the foundation line will facilitate an assesment of the soil to determine whether it has softened or not. If it is established that there is an escape of water and that the subsoil has weakened as a result of the erosion caused by the escaping water, then it is likely that the cost to repair the damage caused by the escape of water will be covered under the relevant house insurance policy.Get Some Quick Advice:If you are concerned that your house or other structure has been affected by what you believe to be subsidence or structural movement and wish to discuss the matter with a suitably experienced engineer, feel free to request a call back by clicking here and filling out the form. Alternatively our contact details can be found by following this link: Contact Us |
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