Unlike most insured perils, subsidence doesn’t stop when you make a claim. It continues quietly, season after season, until the cause is removed or controlled. That’s what makes mitigation both essential and sensitive.
The duty to mitigate
Once evidence shows that a tree is causing movement, the claimant — and by extension their insurer — has a legal duty to take steps to limit ongoing loss. The first action is usually a formal letter to the tree owner setting out the evidence and asking for remedial work.
Historically, insurers favoured tree removal as the surest way to end movement. But the climate-conscious world of 2025 has changed the rules. Urban canopy targets, biodiversity duties and community activism mean that “just fell it” can no longer be the default response.
Why mitigation makes headlines
Requests to remove or heavily reduce protected or council-owned trees attract attention fast. Under the Environment Act 2021, local authorities now have a duty to consult the public before making decisions on subsidence-related tree works. A notice goes on the tree and online for at least three weeks, inviting comments from anyone — not just nearby residents.
Campaign groups monitor these notices closely. A poorly handled consultation can escalate into reputational damage for both the council and the insurer behind the claim.
The Joint Mitigation Protocol
To smooth this process, the insurance and local-authority sectors created the Joint Mitigation Protocol — a voluntary framework setting timelines, evidence standards and communication steps. The 2025 refresh, supported by Defra, the Forestry Commission and the ABI, aims to bring greater consistency and transparency to mitigation decisions. Insurers who adopt it can expect faster cooperation and fewer stalemates.
Choosing the right technical solution
Each site has its own practical limits, but the main options are:
- Tree reduction – Regular crown reductions (every two–three years) can cut a tree’s water demand and stabilise soil movement without felling.
- Root barrier – A subterranean membrane installed between tree and property to block root ingress. Effective but sometimes unfeasible with protected trees.
- Resin injection – Injecting polymer into the soil to fill voids and stiffen the ground. Quick and relatively low-carbon, though performance in clay varies.
- Underpinning – Extending foundations below the active soil zone. Reliable but high in cost, time and embodied carbon.
The carbon dimension
Tree Law’s Subsidence Carbon Calculator lets insurers compare the CO₂ footprint of each option — felling, underpinning, resin injection or root barrier — using real-world data. Early trials show that, in many cases, the carbon cost of removing a mature tree rivals or exceeds the footprint of technical stabilisation.
With regulators pressing insurers to account for Scope 3 emissions (supply-chain activity), being able to evidence a low-carbon decision is becoming as important as showing a cost-effective one.
The insurer’s takeaway
Mitigation is no longer a box-ticking stage; it’s the hinge point where cost, carbon and public perception meet. Insurers who build transparent, data-driven reasoning into this stage reduce both claim spend and reputational risk — while aligning with their own ESG commitments.
