Subsidence, settlement and heave
A willow was stump-ground and the roots were not dug out. Why can a dry summer not rule heave out?
A dry summer cannot rule heave out, because the willow roots were left after the stump was ground. Heave is upward movement when a clay soil takes water back after roots stop drawing moisture. A dry season shows the ground is still dry, not that it will never wet up again. Stump grinding takes the stump down. It does not dig out the root system that may still be in the clay. The survey saw that situation. It has not monitored levels and has not proved or ruled out heave.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Willows are thirsty. While roots are drawing water, a shrinkable clay can fall in a dry spell, which is shrinkage rather than heave. When that demand drops, later rain can swell the same clay and lift the ground. A dry summer keeps the soil on the dry side of that cycle, so the lifting half has not been seen. Roots left in the ground can keep changing how moisture moves. One parched visit cannot close the question.
Tell the solicitor the willow was stump-ground and the roots were not removed, and pass on any tree paperwork the seller has. A ground-movement specialist can consider monitoring if the building shows distortion you need explained. The survey has not ordered that monitoring and has not predicted a season. Do not tell a lender that a dry summer cleared the risk. The roots are still there, and the wet half of the year was not measured.
What should you ask your surveyor?
- Does a dry summer show that clay will not swell later?
- Did stump grinding remove the willow roots, or leave them?
- Has the survey taken levels across more than one season?
What are the typical next steps?
- Treat the dry summer as an unfinished moisture cycle, not a clearance.
- Tell the solicitor the stump was ground and the roots remain.
- Ask a specialist about monitoring if movement must be tracked.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Does stump grinding take away the roots that can affect clay?
No. Grinding reduces the stump at the surface. The roots that were not dug out stay in the ground and can still influence moisture in a shrinkable clay. The survey recorded that the roots were left. It did not excavate them and did not say their effect had ended. Heave stays possible when the soil wets.
Has ground level been watched through a wet season?
No. This visit is one inspection, not a seasonal monitor. A dry summer does not include the re-wetting that would show heave. No series of levels is in the report. Without that record, neither heave nor its absence is proved. A later wet period would be new evidence, not something this survey already holds.