Problems
Concrete settlement
Something has moved and you want to understand whether it will keep moving.
Settlement is the ground beneath concrete losing volume, and the concrete following it down. It is the underlying process behind most sunken and uneven flatwork. Ground that gains volume produces the opposite result, which is why ground that lifts a slab is worth separating from settlement before any lifting is priced.
The reason it deserves its own page is that the fix depends much less on what the concrete looks like than on whether the settlement has finished. A slab lifted over finished settlement stays lifted. A slab lifted over ongoing settlement comes back down. The surface it happens on changes what you notice first, which is why a settled driveway reads differently from a settled walk.
The usual mechanisms
Consolidation of fill: material placed during construction compresses under load over time. This is common where a slab sits over what was once a trench, a basement over-dig, or made-up ground, and it tends to be self-limiting — it finishes eventually.
Erosion: water moving through or under soil carries fine material away, leaving space behind. This does not finish on its own. It continues as long as the water keeps running the same way, which is why downspouts, grading and surface drainage matter so much.
Volume change in the soil itself: some soils shrink as they dry and swell as they wet, moving through cycles with the seasons and with nearby vegetation. This produces movement that comes and goes rather than progressing steadily.
Working out which one you have
Timing is the strongest clue available to a homeowner. Movement that appeared in the first few years after construction and then stopped points at consolidation. Movement that follows heavy rain, or that has continued steadily, points at water. Movement that seems worse in dry summers and eases afterwards points at soil volume change.
None of this is conclusive, and a contractor standing on the site with a probe will learn more in ten minutes than any amount of reasoning from a description. But arriving with a timeline makes the conversation better.
Why the cause changes the fix
Consolidation that has finished: lift it, and it should hold. Erosion: fix where the water goes first, then lift. Soil volume change: expect some ongoing seasonal movement and understand that any fix works within that.
A contractor who quotes a lift without asking about downspouts, grading or the history of the movement is quoting the concrete rather than the problem.
What to ask a contractor
- What do you think is causing this, and what did you look at to decide?
- Do you think this has finished, or is it ongoing?
- What needs to change about where water goes?
- If it settles again after you lift it, what does the warranty do?
Before you ask anybody for a price
Four things worth settling first. None of them needs a contractor, and none of them needs your contact details — they are simply what separates a useful conversation about ground that is still settling from an expensive guess.
Cosmetic, functional or structural
We cannot tell you which of these applies to your property — nobody can from a distance. What follows is how the three differ, so you can look at your own with a clearer question in mind.
- Cosmetic is rarely the right reading for settlement — by the time it is visible at the surface something below has already changed.
- Functional is settlement that has changed where water goes, opened a joint, or put a step where there was none, on flatwork that is otherwise sound.
- Structural is settlement affecting what the building itself rests on rather than what sits beside it. That distinction matters more than the size of the movement.
- The useful question is not how far it has moved but whether it is still moving. Settlement that has finished and settlement that is continuing look identical in a single photograph.
What to record before requesting proposals
Contractors price what they can see. Arriving with these already noted is the difference between quotes you can compare and quotes you cannot.
- Dated photographs of the same spot from the same position, taken at least a season apart. Nothing else distinguishes finished from continuing.
- Where the affected ground sits relative to where the site was worked during construction — near the house, over a trench line, on the filled side of a levelled lot.
- What is discharging water nearby and how often, including irrigation and anything that only runs in one season.
- Whether anything was added to the property before it started — a patio, a widened drive, a raised bed, a filled low spot.
Keep it in the Project Brief if you would rather not lose track of it — it prints to something you can hand to whoever comes out.
Signs that justify getting somebody out sooner
These are observations, not deadlines. Nothing here is a reason to rush a decision; they are the situations where waiting has a cost worth knowing about.
- Doors or windows in the adjacent building have changed how they close since the settlement appeared.
- The movement has continued at a similar rate across more than one full year rather than slowing.
- A crack has opened in something that is holding ground back rather than lying flat on it.
- There is a persistent wet area that does not dry when the surrounding ground does.
What not to assume
- That settlement is always a construction defect. Ground that was cut, filled and compacted keeps consolidating for years, and that is expected rather than negligent.
- That a repair now will hold. On ground that has not finished moving, one correction may not be the last, and an honest assessment says so before the work.
- That the largest visible drop marks the cause. It usually marks the weakest support, which can be some distance from what is actually happening.
- That waiting is always wrong. Where the movement is decelerating, waiting is sometimes the cheapest correct decision.
How we know what this page says
Each of these is something this page says. What follows is why we say it, what we had to assume, and what would change our mind — so you can weigh it rather than take it on trust. How we grade what we publish.
A tree near displaced concrete is not by itself evidence that roots caused it.
Mixed evidence Competent, honest people reach different conclusions here, and the disagreement is real rather than a matter of one side being out of date. Both positions have support and both have failure cases.
Evidence considered
- Roots can and do lift concrete where they grow beneath it.
- Trees and slabs on the same property also respond to the same soil and moisture conditions, producing correlation without causation.
- Removing a mature tree can itself cause ground movement as soil moisture changes.
Still to establish
- Trees and roots — partly, on your own
- Soil movement — partly, on your own
- Subgrade and compaction
Why we say this, and when it may not apply
Root damage is real and common enough to be the first thing people reach for, which means it is also the most frequently misattributed cause. Removing the wrong tree is not reversible.
What we had to assume
- That whether roots are actually under the slab can be established, which often requires excavation.
- That the species and its rooting habit are identifiable.
When this may not apply
- Where roots are visibly under and against the slab, the causal path is direct.
- Where displacement follows the line of a visible root, attribution is much stronger.
What would change it
- Excavation at the edge showing whether roots are beneath the slab.
- The species and mature rooting habit of the tree in question.
- Whether displacement follows the root line or the slab geometry.
Mixed evidence does not mean this: It does not mean the choice does not matter, and it does not mean you should pick whichever is cheaper. It means the deciding factor is usually something specific to your property rather than a general rule.
Movement in concrete that adjoins the house should be treated as a building question until somebody establishes otherwise.
Inspection required This cannot be settled without somebody qualified being present. Not because the question is difficult in principle, but because it depends on something that has to be measured, opened up, or seen in person.
Evidence considered
- Slabs adjoining a building may be independent of it or tied into it, and the two look similar from above.
- Where they are tied, movement in the slab is movement in the structure.
- The distinction generally requires inspection at the junction and sometimes excavation.
Still to establish
- What the concrete adjoins — partly, on your own
- Subgrade and compaction
- Soil movement — partly, on your own
Why we say this, and when it may not apply
It is the one fork in this whole subject where getting it wrong is expensive in a way that cannot be undone later, and whether a slab is independent of the foundation is frequently not visible from the surface.
What we had to assume
- That the junction is accessible enough to be examined.
- That the caution is worth the cost of establishing it, which for anything touching the house it generally is.
When this may not apply
- Where the slab is visibly separated from the building by an open or sealed joint, the question is usually settled.
- Where original construction is documented, it may be answerable from records.
What would change it
- Examination at the junction establishing whether there is a separation.
- Original construction documentation.
- Whether movement is also visible inside the building.
Inspection required does not mean this: It does not mean the situation is serious, and it does not mean you are being pushed toward paying for an inspection. Plenty of things in this category turn out to be minor once somebody looks.
Common questions
How long does settlement take to finish?
It varies enormously with the cause and the material, so any specific figure would be invented. Consolidation of construction fill is often described as taking years rather than decades. Erosion-driven settlement does not finish until the water is redirected. The practical answer is to measure your own: mark it, photograph it, and watch.
Does settlement mean my house is settling too?
Not usually. Exterior flatwork sits on shallow prepared ground; house foundations are built differently and to different depths. A settled driveway is common and rarely says anything about the structure. If you are seeing changes in the house itself — doors binding, cracks in walls, floors sloping — that is a separate question for a different professional.
Work it out, or judge the quote
Related guides
Sunken concrete
A slab that now sits lower than it should — almost always a ground problem, not a concrete problem.
Read more →Voids under concrete
Space beneath a slab — often before anything has visibly dropped.
Read more →Poor drainage around concrete
Where water goes decides how long concrete lasts — and it is the most commonly skipped part of a quote.
Read more →Concrete leveling
Raising settled slabs back toward their original height instead of tearing them out.
Read more →Leveling vs replacement
When lifting is the smart economy and when it is a deposit on a job you will still do.
Read more →