Tree Roots and Ivy Damaging Your Wall: How to Tell, and How to Deal With It
A sapling has taken hold in the top of your wall, or ivy has swallowed a whole run of it, and you are wondering how much damage is going on underneath. Some of it is real and gets worse every year. Some of it is doing no harm at all, and the usual fix makes things worse. Below is how to tell the difference, how to remove growth without pulling the wall down with it, and the rules that apply before you start cutting.
Do tree roots and ivy damage walls?
Tree roots and woody growth inside a wall do cause damage, and it gets worse as they thicken. Ivy is different. Its climbing roots only cling to the surface, and research by Historic England found a covering of ivy can protect stone. Ivy becomes a problem when it roots into the wall itself or grows too heavy.
Ivy: less guilty than its reputation
This surprises most people. Historic England's guidance on ivy says the small aerial roots that hold ivy onto a wall attach to the surface only. They do not penetrate the stone or draw moisture or nutrients from it, and they do not grow bigger with time.
Their research goes further: a covering of ivy moderates temperature extremes and wetting and drying cycles, both of which break down stone and mortar, and it traps airborne pollutants. They are clear that ivy should never be removed just because it looks untidy.
When ivy does become a problem
The trouble starts when ivy produces what Historic England calls proper roots. These form when the base of the plant is cut, when a wall is very damp, or when leaf litter and soil build up in the wall. They push into cracks and gaps, thicken every year, and from then on behave like any other shrub growing in the stonework.
On a dry stone wall that risk is higher, because the whole structure is gaps. The other problem is weight. Once ivy reaches the top of a wall and starts flowering, it becomes large and heavy, especially when wet, and catches the wind like a sail. Historic England's own example of this is a ruined wall at Swarkestone Old Hall, here in Derbyshire.
Tree roots and saplings: always a problem
Unlike ivy, anything woody that is actually rooted in a wall will keep doing damage until it is removed. In our experience these are the patterns we see most:
Saplings in the top of the wall. Sycamore, ash and elder seed straight into the coping and hearting. Each year the stem thickens and levers the stones apart. By the time it is a small tree, the top of the wall is already moving.
Roots from a tree beside the wall. A mature tree close to a wall pushes roots under the foundation course. As they grow, they lift and tilt the base stones, which is one of the common causes of a section starting to lean.
Root heave from a tree that has gone. Remove a big tree and the roots left behind slowly rot, leaving voids under the wall. The settlement shows up years later.
Trees that fall or rock in high winds. A tree rooted hard against a wall takes the wall with it when it moves. We see a lot of this after storms.
If a section has already started to belly out or tip, our guide to why stone walls bulge or lean covers how to judge how urgent it is.
How to tell if your wall is actually being damaged
Six things to check, ideally in winter when growth has died back:
Thick stems coming out of joints, not just lying across the face. Anything thicker than a finger growing out of the wall is rooted in.
Stones lifted or tilted around a stem or near a tree.
Coping stones displaced along the top, especially where ivy has bunched up.
Gaps opening up in the face, or hearting spilling out.
Bulges or lean close to a tree or a heavy mass of ivy.
Soil and leaf litter built up inside the wall, which is what lets ivy root properly.
A wall with a smooth blanket of ivy and none of the above is very likely fine. Leave it, keep it off the coping, and look again next year.
Removing ivy without damaging the wall
The instinct is to cut the ivy at the base and wait for it to die. Historic England specifically advises against this. The attachment roots keep gripping even when the plant is dead, and cutting the base can trigger proper rooting higher up the wall, which is exactly the damage you were trying to prevent.
Their guidance on managing ivy growth sets out the safer approach:
Remove it in small sections, not by pulling whole curtains off, which takes stones and mortar with it.
Take each stem all the way to its growing tip. Any piece left between the cut and the tip will try to root.
Tease out roots that have gone into joints, and cut out larger ones rather than wrenching them.
Use wooden tools rather than metal where the stone is soft or crumbling.
Expect regrowth from dormant buds, and go back over it.
Where roots or stems thicker than about 10mm have been in the wall, Historic England notes the structure may need consolidating or repointing once the growth has rotted away. On a dry stone wall, that usually means taking the section down and rebuilding it.
If the wall is listed or a scheduled monument, Historic England recommends getting advice from their regional office before removing ivy at all.
Removing saplings and roots
Small seedlings in the top of a wall can be pulled out by hand, roots and all, while they are still small. Do it every year and they never become a problem.
Anything established is a different job. Cutting a sapling off at the stone leaves the root inside, and many species simply regrow from it. Pulling out a well-rooted stem levers out the stones around it. The reliable fix is to take down that part of the wall, remove the roots completely, and rebuild it with the hearting packed tight so there is nowhere for the next seed to settle.
For a large tree beside a wall, the decision is whether the tree or the wall gives way. Sometimes the answer is to rebuild the wall with a bridge or lintel over the main root, or to move the line slightly. That is worth talking through on site before anyone reaches for a chainsaw.
The rules before you start cutting
Nesting birds
Ivy and old walls are prime nesting spots. Under section 1 of the Wildlife and Countryside Act 1981, it is an offence to intentionally take, damage or destroy the nest of any wild bird while it is in use or being built. Check carefully before clearing ivy or scrub, particularly in spring and summer, and if there is an active nest, wait.
Protected trees
If the tree is covered by a tree preservation order, or you are in a conservation area, you may need your council's permission before cutting it or its roots. Plenty of Derbyshire villages sit inside conservation areas, so check before work starts.
Your neighbour's tree
GOV.UK's guidance confirms you can trim branches or roots that cross into your property from a neighbour's land, but only up to the boundary. Go further and your neighbour could take you to court for damaging their property. The protected tree rules above still apply.
Cutting roots close to a tree can also kill it or make it unstable, which then becomes your problem. Talk to the neighbour first, and if the wall sits on the boundary, our guide to who is responsible for a boundary wall covers who pays for the repair.
Keeping it from coming back
Most of this comes down to a few minutes a year:
Pull seedlings out of the coping every autumn.
Keep ivy below the coping, so it never gets heavy enough to catch the wind.
Clear leaf litter and soil from the top and the base of the wall.
Do not plant trees right against a wall. Give them space.
Deal with gaps quickly, because a hole in the hearting is a seedbed.
When the roots have already done the damage
Once a tree or rooted ivy has opened the wall up, removing the growth is only half the job. The stones it has pushed apart will not go back on their own, and the section needs taking down and rebuilding properly.
We clear root-damaged and overgrown walls and rebuild them across Derbyshire, from garden walls to long field boundaries. Send us a photo and a postcode and we will tell you whether it needs a rebuild, or whether the ivy is best left exactly where it is.
Comments