Subsidence, settlement and heave
How should a buyer separate a willow, a heave crack and the drain run under the canopy when all three are mentioned together?
Separate the tree, the crack and the drain. A willow under whose canopy a drain runs can dry clay and, after felling or heavy pruning, the ground can swell, but this survey has not shown that the crack is heave. It also has not tested the drain. The visit recorded a willow, a crack described in heave terms, and a drain line under the canopy. Those are three observations. None of them has been proved to be the cause of the others.
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?
Willow roots take moisture from shrinkable soil. When that demand drops, clay can heave and lift masonry, often with cracks that are wider at the top or that taper in a way associated with upward movement. A leaking drain under the same canopy can soften the ground or wash fines out, which is a different mechanism and can look similar at a glance. This inspection did not excavate the drain, did not monitor the crack and did not test the soil. The three notes must stay unjoined.
Tell the solicitor the willow, the crack and the drain are recorded together but not proved as one claim. An insurer or a structural specialist may want monitoring and a drain test before anyone names heave. That work is outside this report. A lender should be told the cause is undecided, not that the house is subsiding or heaving. Ask who owns the willow if it stands off the plot, because pruning rights are a separate paper question.
What should you ask your surveyor?
- Was the crack only described, with no monitoring readings taken?
- Was the drain under the willow canopy left untested?
- Has the report kept heave as a possible reading rather than a finding?
What are the typical next steps?
- Keep the willow, the crack and the drain as three separate notes.
- Tell the solicitor the cause of movement is not proved.
- Ask a specialist about monitoring and a drain test if you need a cause.
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 clay soil always heave when a willow is cut?
No. Heave is a possible response of shrinkable clay when moisture demand falls, not an automatic result of cutting a willow. This survey did not test the soil and did not record a felling date. The crack stays a visual note until monitoring or a specialist separates heave from drain movement or ordinary shrinkage.
Who should look at the drain if the joints are suspect?
A drainage contractor with the right access, not the home survey. The visit did not test the run under the canopy and did not open the joints. Ask the solicitor whether any drain guarantee or CCTV report already exists. Until that work is done, do not tell a lender the willow cracked the pipe or that the pipe lifted the wall.