Trees, Clay and Two Cracking Houses: Subsidence Proved, Then Repaired

The loss

Cracking to two neighbouring houses in south west London, on London Clay, with mature trees close by: the classic ingredients of a subsidence claim. Subsidence is the peril where the diagnosis is the claim, because until the cause is proven, nobody can say what the repair is, what it costs, or whether it will hold.

The brief

Acting in the claim across both properties, Avalon’s job was to establish the cause with evidence that would satisfy the insurer, specify the right repair rather than the biggest one, and administer the works through to account.

Investigation before opinion

The investigation was run as a programme, not a site visit. Trial pits were excavated at agreed locations to expose the foundations and the ground beneath them. Laboratory soil testing confirmed high plasticity clay with significant desiccation to a depth of two metres, ground that shrinks as it dries. Roots recovered from the trial pits were sent for identification, narrowing the vegetation implicated, with a high water demand poplar standing within influencing distance of the rear of the property. An arboricultural subsidence report assessed the trees, and precise level monitoring was run over time at fixed stations on both houses, with the readings graphed, because clay-shrinkage subsidence is proved by movement over seasons, not by a photograph of a crack.

From cause to repair

With causation evidenced, geology, desiccation, roots, vegetation and monitored movement all pointing the same way, the findings were drawn together in summary and update reporting so the claim could move, and the repair works were then specified, valued and carried through to a final account within the claim.

The outcome

Two houses investigated to laboratory standard, a cause the insurer could accept, a proportionate repair delivered and accounted for, and a claim that moved on evidence at every step. In subsidence, the cheapest part of the project is proving the cause properly; everything built on a wrong diagnosis is money spent twice.

Services demonstrated

Insurance Claims (subsidence and tree-related damage, the practice’s most frequent claim type); investigation programme management (geotechnical, arboricultural, root identification, level monitoring); Costing; Contract Administration of repair works to final account.