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Crack sealing vs crack filling
Should the crack be sealed or filled? What is the difference?
One question decides it: does the crack still move? Sealing uses a flexible material that can stretch as the crack opens and closes. Filling uses a rigid material that restores a continuous, wearable surface but cannot accommodate movement.
Choosing on price rather than on crack behaviour is the most common way this goes wrong, in both directions.
What it is
Sealing places a flexible sealant into the crack, bonded to both faces, designed to move with them.
Filling places a rigid cementitious or resin material into a stable crack and finishes it flush so it can be walked and driven on.
Both are surface-level crack treatments. Neither restores structural continuity and neither addresses why the crack formed.
What it does not do
- Neither stops movement or addresses settlement, voids, or the cause.
- Neither makes the crack invisible.
- Neither is a structural repair.
- Neither is appropriate where there is vertical displacement across the crack.
Sealing (flexible) vs Filling (rigid)
| What differs | Sealing (flexible) | Filling (rigid) |
|---|---|---|
| Behaviour when the crack opens and closes seasonallyThis is the single deciding row. Two dated measurements of the crack, a season apart, answer it. | Designed for it — stretches and recovers | Not designed for it — tends to crack through or debond |
| Ability to carry traffic and wearOn a driveway wheel path, a rigid filler survives traffic better — provided the crack is stable enough for it. | Softer; can be worn or picked out in trafficked areas | Wears more like the surrounding concrete |
| Appearance when finishedWhere appearance is the main motivation, filling gives the better result — again, only on a stable crack. | A visible line, usually a different colour and texture | Closer to the surrounding surface, though rarely invisible |
| Tolerance of a damp crack at the time of work | Some sealants tolerate damp better | Generally needs a dry, clean crack to bond |
| What failure looks likeIf a previous repair reproduced the crack line exactly, that is evidence a rigid material was used on a moving crack. | Loses adhesion at an edge, or wears away in traffic | Cracks through the middle, reproducing the original line |
Where they genuinely overlap
- Both keep water and debris out of the crack while intact
- Both benefit substantially from routing the crack out first
- Both are surface treatments with no structural function
- Both leave the cause of the crack untouched
- Both look better on a routed, regular channel than on a ragged crack
What changes the answer
- Whether the crack has measurably moved between two dated observations
- Whether traffic runs across the crack
- Whether appearance or water exclusion is the primary goal
- Whether a previous repair failed, and how it failed
- Whether the crack is damp at the time of work
The cheaper first number is not the cheaper decision. The cheaper option here is not the cheaper decision if it is the wrong one. A rigid filler in a moving crack fails and reproduces the original line, so you pay for the repair and then still have the crack — and the second attempt starts from a surface that has been disturbed. Establishing stability first, with two dated measurements, costs nothing and is what makes either choice durable.
Questions to ask whoever comes out
- How have you established whether this crack is still moving?
- Which are you proposing, and what happens if the crack behaves differently than you expect?
- Is routing included, and what difference does it make here?
- How closely will the finish match?
- What does your warranty cover if it reopens?
Where estimates for this commonly differ in scope
These are the places two prices for apparently the same work stop being comparable.
- Routing is the biggest hidden price difference and applies to both.
- Per-crack versus per-linear-foot pricing changes totals substantially.
- Estimates rarely state whether they assumed a moving or a stable crack.
Usually worth planning a repair
Conditions in this band do not usually become emergencies, but they rarely improve on their own and repair costs tend to rise with the affected area.
Who tends to do this work
- 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.
Common questions
How do I know if my crack moves?
Mark across it with a pencil, write the date beside the mark, photograph it with a scale, and repeat after a season. Two dated observations answer the question that decides this comparison. It is the cheapest useful thing you can do before spending money on either option.
Which one looks better?
Filling, generally — it restores a continuous surface rather than leaving a soft line. But it only looks better if it survives, and on a moving crack it does not. On a moving crack a well-executed seal looks better than a failed fill.
Can I do both?
They occupy the same space, so not in the same crack. What is genuinely worth combining is routing plus whichever material suits the crack — preparation improves both options more than switching between them does.
Where to go next
Methods that may apply
Related problems
What drives the cost
Want a straight answer about sealing vs filling?
Both decision tools are free and need no contact details. If you would rather have somebody local look at it, you can ask us to review whether we can match you — and we will say plainly if we cannot.