Tree-root damage to concrete

You can, and it will very likely happen again, because the root is still growing. This is the condition in the library where the concrete repair is the easier half of the problem and the decision about the tree is the harder one.

It is also a decision that a concrete contractor is not usually the right person to make, and that homeowners frequently make by default — by accepting a scope that cuts whatever is in the way.

What it is

Roots grow where conditions favour them, and the ground under a slab is often favourable: moisture is retained, temperatures are moderated, and there is no competition. A root that grows under concrete and then thickens has nowhere to expand except against the slab above it.

The result is usually localised. A single panel lifted, a crack running along the line of a root, an edge tilted upward — concentrated over the root rather than spread across the area, which is what distinguishes it from settlement or general heave.

Root-related displacement is progressive and does not reverse. That is a genuinely useful diagnostic: seasonal movement suggests frost or moisture, while movement that only ever increases suggests something growing.

What seeing this cannot establish

• The presence of a nearby tree does not establish that a root is under your slab, and the absence of visible roots does not establish that there is not one.
• Which tree a root belongs to is frequently not obvious, particularly where several are within range.
• Nothing visible from the surface tells you how large the root is or how much of the slab it runs under, which is what determines the repair scope.
• This page cannot tell you whether cutting a given root will harm or destabilise the tree. That is genuinely an arborist's assessment and the consequences of getting it wrong include losing the tree or, worse, having it fail.

What this can be associated with

Candidate explanations, not findings. Nobody can establish which applies to your concrete without seeing it.

• A tree within a distance comparable to its mature height, whose roots extend well beyond its canopy
• Moisture retained beneath the slab, which can make the ground under concrete attractive to root growth
• Species with vigorous shallow root systems, which some are and some are not
• A slab poured directly on grade with no root barrier and no base depth to speak of
• Irrigation or a leaking line near the slab drawing roots towards it

What you can safely check yourself

• Photograph the displacement and the nearest trees in the same frame if you can, so the relationship is visible.
• Note whether the displacement is localised over a line, which is consistent with a root, or spread across an area, which is more consistent with settlement or general heave.
• Look for surface roots elsewhere in the lawn running towards the slab. Where they surface, they indicate direction.
• Check whether the movement has ever reversed. Root displacement does not; frost movement often does.
• Photograph any cracking that follows a line rather than a joint or a corner.
• Measure the lift and date it, so progression can be established.

When this is frequently cosmetic

• Slight tilt with no trip lip, no drainage change and no cracking
• A raised edge in an area nobody walks on, where appearance is the only consequence

When professional evaluation matters more

• A trip lip has formed on a walkway or step
• Displacement is increasing between dated observations
• The concrete has cracked rather than simply tilted
• The root is approaching a foundation, a wall, or a service line rather than only flatwork
• The tree matters to you, in which case an arborist's view is worth having before anyone cuts anything

When replacement enters the conversation

• The root needs removing or rerouting, which generally means removing the concrete above it
• The panel has broken up rather than lifted intact
• Repeated grinding has already been done and the lip keeps returning
• The base needs rebuilding with a root barrier, which cannot be done through the slab

Evidence worth having before you ask for estimates

Every item here is something you can produce without tools or risk, and every one of them makes an estimate more accurate.

• Photographs showing the displacement and nearby trees together
• A measurement of the lift, dated, and a repeat measurement later
• Notes on whether movement has ever reversed
• Photographs of surface roots and their direction
• The species of the tree if you know it, and its approximate height and trunk diameter
• Whether the tree is protected by any local ordinance, which is worth checking before assuming it can be cut

Questions to ask whoever comes out

• Do you think a root is under this, and how confident are you without opening it up?
• Does your scope include cutting a root, and if so, have you or the owner had an arborist advise on it?
• If the root is not addressed, how long would you expect the repair to last?
• Would a root barrier be worth installing while the concrete is up?
• What happens if you find a much larger root than expected once you start?

Where estimates for this commonly differ in scope

These are the places two prices for apparently the same work stop being comparable.

• Root cutting is often included in a concrete scope without any arboricultural assessment. That is the single biggest gap in estimates for this condition.
• Grinding a lip and addressing a root are entirely different scopes, and grinding is often quoted without saying that the cause remains.
• Root barriers may or may not be included, and they are considerably cheaper to install while the concrete is already up.
• Tree removal, if it comes to that, is a separate trade, a separate price, and sometimes subject to local rules.

Who tends to do this work

• A residential flatwork concrete contractor
• A concrete repair specialist

ConcreteOwner does not inspect, certify or approve contractors. This describes which trade usually holds this work, not a recommendation of anybody in particular.