Trees and subsidence: evidence before consenting removal

Tree subsidence evidence for removal has to do one thing: show, with measurements rather than opinion, that this tree is causing this damage and that nothing short of felling will stop it. A crack in a wall and a large tree in the garden is not evidence. Councils refuse applications on that basis every month, and a refusal that could have been avoided costs a season, because the monitoring has to run through a full summer before anyone can draw a conclusion.

If the tree is covered by a Tree Preservation Order, or stands in a conservation area, you need the authority's consent or notice before any work. Subsidence is not an exemption. The exemptions in the 2012 Regulations cover dead trees and work urgently necessary to remove an immediate risk of serious harm, and a crack in a wall is neither.

What the authority needs to see

Tree officers work to a recognisable evidence set, and many authorities apply the Joint Mitigation Protocol produced by the London Tree Officers Association, which sets out what should be submitted before a tree is removed on subsidence grounds. Submit less than this and you will get a request for more.

The arboricultural report should sit alongside the engineering evidence rather than inside it. Where a formal survey exists for the site, the Tree Survey gives the officer the baseline they need on condition and amenity value.

Soil, level and crack monitoring

Clay shrinkage subsidence is seasonal. Shrinkable clay loses moisture through the growing season, the ground drops, and the building moves with it, then partially recovers over winter. That cyclical pattern is the signature the officer is looking for, and you cannot show it without a year of readings.

Precise level monitoring means fixed studs on the building read by a surveyor to a consistent datum, monthly or at least quarterly, for twelve months and ideally longer. Crack monitoring uses demec studs or tell-tales across the cracks, read at the same frequency. Photographs with a scale alongside are useful corroboration and are not a substitute.

The soil work decides whether the mechanism is even possible. A trial pit at the affected corner establishes the foundation depth and type, and samples from below foundation level are tested for plasticity to grade the clay's volume change potential. A desiccation profile then shows whether the soil beneath the foundation is drier than it should be at that depth, which is the direct evidence of moisture extraction. On sand or gravel, clay shrinkage is not the mechanism and the investigation should say so and look elsewhere, often at drainage. The relationship between roots and drains is a separate problem, covered in tree roots and proximity to a public sewer or drain.

Linking the tree to the damage

Three links have to close, and most refusals turn on the second or third.

1. The tree is close enough and has sufficient water demand. Distance is judged against mature height and species water demand, with oak, poplar, willow, elm and some species of cherry at the high end and many ornamentals much lower.
2. Roots of that species are present beneath the affected foundation. This is why root identification from the trial pit matters. Finding roots is not enough; finding roots that a laboratory identifies as the species of the tree you want to remove is.
3. The movement pattern is consistent with that tree. Damage that is worst on the elevation furthest from the tree, or movement with no seasonal cycle, points to another cause such as leaking drains, made ground, heave from a previously removed tree, or thermal movement.

Where more than one tree could be responsible, including trees on neighbouring land, say so. An application to remove a protected tree in your garden while an unprotected willow next door goes unmentioned will be refused, and reasonably so.

Alternatives to felling that have to be tested

The authority will ask what else was considered. Answer it in the application rather than waiting to be asked.

Root pruning with a barrier can work where the roots arrive from one direction and the building can be approached, though barriers need to be deep enough to reach below the influencing root zone and the excavation itself risks destabilising the tree. Crown reduction is widely offered and widely doubted: reducing the canopy reduces water demand for a period, and the regrowth returns it, so a cyclical pruning programme has to be funded and committed in writing to count as a solution. For a mature tree of high amenity value, a committed management programme with a named arboriculturist is sometimes accepted where felling would not be.

Partial removal of a group, taking the nearest tree and retaining the others, is often the outcome a tree officer will agree. Offer it.

Engineering solutions and deeper foundations

Underpinning transfers the foundation load below the zone of seasonal moisture change and removes the problem without touching the tree. It is disruptive and costly, and insurers resist it where felling costs less, which is exactly why a tree officer will raise it.

Be straight about the comparison. Where the tree has high amenity value, stands in a conservation area, or contributes to the character of a street, the planning balance can favour deepening the foundations or repairing the superstructure even though it costs more. Mass concrete and piled beam solutions, and root barriers combined with repair, are all legitimate answers, and a scheme that has priced them and explained why one was chosen reads very differently from one that asserts felling is the only option. Where ground investigation is needed to design any of this, the scope belongs in a Geotechnical Assessment.

Insurance involvement and timing

Most subsidence claims run through an insurer, who appoints a loss adjuster and usually an engineer. That process produces much of the evidence the council wants, which is helpful, and it produces it on the insurer's timetable, which is often not.

Two points to hold onto. The council is not bound by the insurer's conclusion, and an engineer's letter recommending removal, without the soil, root and monitoring evidence behind it, carries little weight with a tree officer. And the twelve month monitoring period does not start when the claim is made; it starts when the monitoring is installed, so press for installation early.

The Regulations provide for compensation for loss or damage caused by a refusal of consent under a Tree Preservation Order, subject to conditions and a minimum threshold, and a claim has to be made within a set period of the decision. That is a real route where a refusal leads to continuing damage, and it is one reason authorities take these applications seriously. Take advice before relying on it.

Replacement planting and what happens next

Consent to remove a protected tree normally comes with a condition requiring a replacement, in a position and of a species the authority agrees. That is the moment to choose something with low water demand and a modest mature size rather than accepting a like-for-like replacement near the same foundation.

Expect the replacement condition to carry a maintenance obligation of several years, with failures to be replaced in the next planting season. The mechanics are the same as for new planting generally, set out in the five year maintenance condition on new planting.

If consent is refused, there is a right of appeal to the Planning Inspectorate within 28 days of the decision, and the appeal is decided on the same evidence, so a weak application produces a weak appeal. Fix the evidence first. What the officer will look at on a site visit, and how they weigh condition against amenity, is set out in tree officer site visits and what they inspect.

This is general guidance, not legal advice. Check the position with your local planning authority's tree officer and take advice from a qualified arboriculturist and structural engineer before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval.