Southwark Council with so many tens of thousands of trees receives a number of lciams for subsidence caused by those trees routes every year.

The latest stats I have after submitting a Freedom of Information request:
2010   69 claims
2011   70
2012   47
2013   41
2014   34 claims – but residents have up to 6 years to make a tree subsidence claim

Average time to resolve – 12-18 months to resolve a subsidence claim which is apparently is pretty average for councils. The council logs when a claim is raised and when the claim file is ultimately closed. However this does not measure how long a claim takes to resolve. For instance, a building insurer may raise a claim, ask for initial pruning to be introduced and then the claims handlers hear nothing further from the claimant. However they are required to keep the claim open for a significant period of time in case further communication from the claimant is received.

Tree root liability claims take longer to resolve than most other types of public liability claims as various sets of technical data are generally required along with a period of movement monitoring through a growing cycle, normally 12 months.

Top 3 Reasons cases take longer than the industry average/ best practice:
1. Technical data is not complete or provided – the council must ensure that the technical data is sufficient to show the cause of the subsidence before it moves to take remedial action, especially if it relates to a tree removal. People get very upset when well loved trees have to be removed. Occasionally a further period of monitoring may be required if the monitoring results did not show significant movement or the nature of movement was inconclusive requiring additional period of monitoring. There may be another cause to subsidence movement such as leaking drains, or unusually wet or dry periods.
2. Receipt of arboriculture reports – speeding up this process would in particular improve the average time to resolve the smaller less complex claims such as boundary walls and driveways.
3. Challenge to proposed tree removal – once the process begins to fell trees, delays can arise when challenges are received to the proposed felling. In addition this can also impact the speed at which arboriculture reports can be finalised.