Short answer
Sometimes, but usually not in the way people expect. Roots are generally not strong enough to push through sound, intact concrete. The more common problems are indirect: large trees can draw moisture out of certain soils, and roots can exploit cracks that already exist. Light structures such as paths, steps and patios are more likely to be lifted than a well-built foundation.
Risk depends on the tree species, the size of the tree, the distance to the house, the soil type and the condition of the foundation. If you are seeing cracks, get the cause assessed rather than assuming the tree is to blame, or assuming it is not.
How roots can cause foundation problems
Soil moisture and shrinkage
This is generally considered the main route to damage. Large trees take up a lot of water. In clay soils that shrink as they dry and swell as they get wet, a thirsty tree close to the house can contribute to uneven soil movement beneath a footing. When part of the foundation loses support, it can settle unevenly, and cracks may follow. Sandy or well-draining soils are usually less prone to this kind of movement.
Roots using existing cracks and gaps
Roots grow where they can find water, oxygen and loose soil. They tend to follow the path of least resistance, so a small crack, a failed joint or a gap around a pipe can become an entry point. Once inside, a root can thicken over time and widen the opening. In this case the crack usually came first.
Lifting and pressure on lighter structures
Surface roots that thicken beneath sidewalks, driveways, patios and steps can lift and crack them. These are visible, but they are not the same as structural foundation failure. Fixing them is mostly about the tree and the paving, not the house.
Which trees and soils carry more risk
Fast-growing trees with large canopies and high water demand are often cited as higher risk close to buildings, especially in expansive clay. Willows, poplars, and some large maples and elms are commonly named, though any big tree planted too close can cause trouble. For a closer look at one frequently mentioned example, see our article on hybrid poplar roots. Maples are covered in are maple trees messy.
Roots do not only grow straight down. Most of the roots that take up water and nutrients sit in the upper layers of soil and can spread well beyond the edge of the canopy. That is why a tree that looks a safe distance away can still affect soil near a house.
How close is too close?
There is no single safe distance that fits every tree. A rough rule often repeated is to keep large trees at least as far from the house as they will be tall at maturity, with more distance for water-hungry species on clay soils. Small, slower-growing trees can usually go closer. When in doubt, check the mature size on the plant label, and consider our list of small trees with shallow, non-invasive roots for tight spaces.
Signs roots may be involved
- Diagonal or stair-step cracks in brickwork or walls, especially near a large tree
- Doors and windows that start to stick or no longer close properly
- Gaps opening between walls and ceilings or floors
- Sloping floors
- Cracks that open more in dry summers and partly close after rain
- Visible roots lifting paving beside the house
Many of these signs also have other causes, such as poor drainage, leaking pipes, original construction issues or normal settling. Roots are one possibility, not the only one.
What to do if you suspect root damage
- Document it. Photograph cracks and note the date. Some people mark crack ends with a pencil to see if they grow.
- Get a professional opinion. A structural engineer or qualified foundation specialist can assess whether movement is happening and why. An arborist can advise on the tree.
- Check pipes. Roots can also affect drains. See tree roots in your sewer line for the warning signs.
- Do not remove the tree in a hurry. In some clay soils, removing a large mature tree can cause the soil to re-absorb water and swell, which may cause movement of its own. Get advice first.
Cutting or removing roots near the house
Cutting large roots can harm the tree and may make it less stable, which is a safety issue near a building. Cutting should generally be done or guided by a qualified arborist, who can judge which roots are safe to remove and how far from the trunk to cut. Thicker roots deserve particular caution.
If you plan to remove a tree, the stump and roots will break down over years. Some people ask about pouring concrete over dead roots. Decaying roots can leave voids and the soil above them can settle, so it is usually better to get advice from a contractor before building over them.
For roots growing above ground near the house, options include covering shallow roots with mulch or soil, adjusting paving, or having an arborist assess whether selective pruning is appropriate.
Preventing problems
- Choose trees whose mature size suits the space. See best shade trees for backyards for options by yard size.
- Plant away from foundations, drains and sewer lines.
- Water young trees deeply and less often so roots are encouraged to grow down and out rather than hugging the surface.
- Repair cracks and leaking pipes promptly, since moisture draws roots.
- Consider a root barrier in some situations, ideally installed by a professional, as barriers can fail if poorly designed or placed.
FAQ
Which tree roots damage foundations?
Large, thirsty, fast-growing species such as willow and poplar are the usual suspects, but the soil and distance matter as much as the species.
Can tree roots cause cracks in walls?
They can contribute, mainly by affecting soil moisture beneath a foundation. Other causes are common, so have cracks inspected.
Can I pour concrete over dead tree roots?
It is generally not recommended without advice, because decaying roots can leave voids and cause settling.