Optera specialise in both rehydration channels and root barrier schemes for properties built on clay soils. These methods of intervention offer fast, non-disruptive ways of arresting movement earlier in the claim lifecycle, mitigating damage and reducing claim cost to the insurer as well as disruption to the homeowner.
Clay is unique in that it holds water as part of its molecular structure and water-demanding trees extract the water, reducing the volume of the soil. It is when foundations are supported by this shrinkable clay that the stability of properties can be affected. Removing the trees has for a long time been seen as the most secure approach; however, the insurance industry has historically struggled to provide a solution which satisfies all parties, for example when the tree is either owned by a third party who refuses to cooperate or is owned by a local authority. Recent legislation and case law have made the position even more onerous to resolve. Recognising this, Optera have worked with insurance suppliers to implement solutions that allow the tree to remain whilst ensuring the long-term stability of the property without the need for disruptive and intrusive underpinning.
Rehydration channels and root barriers are both significantly cheaper to install than large-scale substructure intervention schemes. They can be implemented at an early stage of a claim at minimal expense and can therefore significantly reduce the claim lifecycle. Without these two options, claims have historically experienced delays and uncertainty whilst third-party negotiations are undertaken or whilst sufficient monitoring and site investigation data is collated, all the while potentially exacerbating the damage above ground. By offering solutions which enable the vegetation to remain, Optera are not only speeding up the repair cycle, but also bringing to the industry schemes which reduce the carbon footprint and environmental impact of a project.
Utilising the principles of sustainable urban drainage schemes, we implement a process whereby rainwater is diverted and harvested in underground channels between the tree and the affected property. Boreholes are extended through the base of the channel and filled with a granular material which acts as a sponge, irrigating the soil on demand and preventing the moisture content within the clay from reducing sufficiently to shrink.
This sustainable process is designed with our consultant arborist and is suitable where trees have statutory protection. Both rehydration channels and root barriers are used in cases of clay shrinkage and provide a useful alternative to removal which may be refused in the case of statutory protection or where a third-party owner refuses cooperation. Care should be taken to avoid heave and advice should always be sought before undertaking tree works.
A root barrier is an impenetrable membrane which is placed between a tree and the affected structure. It severs existing roots and prevents new roots from going beneath the building. Historically, root barriers were not considered an effective long-term solution, primarily because the roots could go around or under the membrane, or the membrane itself would perish and fail, allowing new roots through. Traditionally, barriers were generally damp-proof membranes which, although impenetrable, were also impermeable and so potentially hindered the passage of ground water and also degraded over time.
Optera, working closely with our consultant arborist, design specially formulated barriers which are commonly positioned between the tree and the affected structure for maximum effect.
The specially formulated geotextile provides not only a physical barrier to roots but also incorporates a repellent. The roots are diverted from the barrier due to the repulsion, preventing roots from massing against it. A trench is dug, the barrier is installed and the hole is back-filled with either the dug material or, where we are particularly close to house foundations, the trench is back-filled with a lean-mix concrete to ensure there is no settlement. The severed roots will naturally die and no longer demand moisture allowing the clay to naturally rehydrate.
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