Mature boundary trees are common on the older streets we work across, and they change the job in two ways: you cannot always dig where you want, and cutting the wrong root can be both harmful and, where a tree is protected, unlawful.
Diagnostic timeline
Work through these steps in order before booking a repair.
- 1
Check whether the tree has a Tree Preservation Order or sits in a conservation area — your council's map will show it.
- 2
Probe the line at each intended post position before committing to a spec.
- 3
Look at how the existing fence has moved: lifting usually means roots, leaning usually means bases.
Likely causes
Root plate under the fence line
Major structural roots often run exactly where posts want to go.
Root growth over time
Roots thicken and lift posts, gravel boards and paving slowly but irresistibly.
Soil heave and shrinkage near trees
Clay shrinks as a tree draws moisture in summer and swells again in winter, moving shallow bases.
Fix options, full-width
Offset the post positions
Roots occupy only part of the lineBays are re-spaced so posts land in clear ground rather than through roots.
Hand-dig and set off the roots
Roots are present but avoidableNo augering; posts hand-dug and set clear so nothing structural is severed.
Bolt-down or spiked post supports
Digging near a protected tree is not permittedPosts mounted to existing hard standing or driven supports avoid excavation altogether.
Post-and-rail with wire
Green-belt or wooded boundariesA lighter structure that tolerates ground movement without cracking or leaning.
Get this fixed properly
Free site visit across London and Hertfordshire, a written specification and a fixed price before anything starts.
Prevention
- Get an arboricultural opinion before working inside the root protection area of a protected tree
- Design the bay spacing around the tree instead of forcing a regular grid
- Leave a movement gap where roots are actively growing towards the line
Frequently asked
Can I cut roots to fit a fence post?
Small roots often, structural roots no — and for protected trees you may need consent. We advise at the survey.
What is a TPO?
A Tree Preservation Order restricts works to a tree; councils publish which trees are covered.
Will a fence damage my tree?
Properly planned, no. Severing major roots or compacting the root zone can.
Do you work with tree surgeons?
Yes, we coordinate where an arb report or pruning is needed first.