Yes, you can resurface a cracked concrete driveway in many situations, but whether you should depends entirely on what kind of crack you have. Hairline surface cracks can be resurfaced over directly. Moderate cracks need repair before the overlay goes down. Structural or moving cracks may mean the slab is past resurfacing and replacement is the more cost-effective answer. Cement Concrete & Aggregates Australia, concrete basics provides technical context on concrete behaviour. Our guide to what to do about a cracking driveway covers the broader picture. This guide focuses specifically on the resurfacing decision.
The short answer, and the honest caveats
Resurfacing works over cracks when:
- The crack is hairline (under 1 mm), stable and not moving
- The slab is otherwise sound: no significant spalling, no rebar showing, no sub-base failure
- Crack repair or injection is completed before the overlay goes down
Resurfacing does not work when:
- The crack is structural, actively moving or caused by sub-base failure
- The slab has lifted sections, significant differential settlement or major spalling
- The crack will continue to move after resurfacing, meaning it will telegraph back through the overlay
A crack that looks cosmetic from above can still be a sign of movement below. This is why an on-site inspection by a qualified contractor matters before any resurfacing decision is made.
Hairline vs structural cracks: how to tell them apart
The distinction between hairline and structural is not always visible from the surface, but there are signs that help.
Hairline cracks (under 1 mm wide): These are typically surface-shrinkage cracks that develop as concrete dries and cures. They are usually shallow, do not extend through the full depth of the slab and are not moving. They appear in irregular patterns across the surface rather than following a consistent line. Resurfacing over hairline cracks, with the crack filled with a flexible caulk before overlay, is standard practice.
Moderate cracks (1-5 mm wide): These cracks may or may not be stable. Edges slightly different in height on each side of the crack suggest movement has occurred. These need proper crack injection, typically with a flexible polyurethane or two-part epoxy grout, before resurfacing. The choice of injection material depends on whether the crack is still moving.
Structural cracks (over 5 mm, or any width with visible heave or settlement): These indicate that something is wrong with the sub-base or that significant loading has exceeded what the slab was designed for. Resurfacing over a structural crack is a short-term solution at best. Our guide on resurfacing vs replacing concrete helps frame that decision.
Movement cracks that will reappear through any overlay
The most common resurfacing failure is an overlay applied over a crack that continues to move after the job. Concrete expands and contracts with temperature. A crack that developed because of differential settlement or root pressure is still subject to those forces after the overlay is applied. Within one to two summers, the crack re-appears in the overlay surface exactly where it was before.
A simple field test: using a piece of chalk, mark the ends of the crack clearly and note the date. Return in a month and check whether the marks have moved relative to the crack. If the crack has extended or widened, it is active. Active cracks need stabilisation before any overlay work, not just filling.
If the source of movement is tree root pressure, the root issue must be addressed before resurfacing. Resurfacing over a root-heaved section without removing or managing the root simply delays the return of the heave by a season or two.
Standard crack-repair steps before resurfacing
For hairline to moderate cracks that are stable, the repair process before resurfacing typically involves:
- Chase the crack out slightly with an angle grinder or crack chaser to create a clean V-shaped or square profile. Filling into a clean profile holds better than filling into a feathered crack edge.
- Clean out dust and debris with compressed air or a vacuum.
- Apply crack filler: flexible polyurethane caulk for hairline, two-part injection resin for moderate cracks, epoxy mortar for wider gaps.
- Allow full cure per product specification before grinding and overlay.
This process is part of good prep practice on our driveway resurfacing service. A contractor who skips this step and simply covers cracks with overlay is cutting a corner that will show up within a year.
Spalling alongside cracks should be addressed at the same time. If the surface layer is delaminating around a crack, the spalled area needs to be ground back to sound material before the overlay goes down. Our guide on spalling concrete repair covers that in more detail.
When the slab is beyond resurfacing (and replacement is cheaper long term)
There are situations where a quoted resurfacing job is not the honest recommendation. Signs that a slab is past a practical resurfacing solution:
- Multiple wide cracks with noticeable height differences between slabs
- Severe spalling across more than 30-40% of the surface area
- Visible rebar showing through the surface, especially with rust staining
- Sections that sound hollow when tapped (delaminated sub-base)
- Ground settlement visible as a dip or bow in the slab
If these signs are present, the overlay will follow the movement of the slab beneath it. You are paying for a new surface on a failing structure. The result looks good for twelve to twenty-four months and then deteriorates rapidly. Our guide on concrete cancer vs spalling covers the difference between surface damage and structural damage, which is worth reading if you see rebar staining.
In these cases, replacing the slab or at minimum the affected panels is usually a better use of money over a five to ten year horizon.
Central Coast context: reactive soils and tree-root cracks
The Central Coast has pockets of reactive soil, particularly in areas with clay-based sub-bases. Reactive soils expand when wet and contract when dry, creating a low-level seasonal movement that can cause shrinkage cracking in slabs over time even without tree roots. This type of cracking tends to be shallow and diffuse rather than localised, and is often manageable with standard crack repair before resurfacing.
Tree roots are a more significant challenge in established suburban streets. Figs, camphor laurels and large gums are particularly common around older Central Coast driveways and can produce root pressure that lifts entire slab panels. A lifted panel that has been pushed off its sub-base may look cracked at the surface but is actually a structural problem: the sub-base is missing or displaced beneath it. Simply grinding the lifted edge flat and resurfacing over it does not address the root or the sub-base gap.
For root-related cracking, the repair sequence is: address the root (removal, barrier or cutting back), compact or re-fill the sub-base void, and then assess whether the panel is worth resurfacing or needs replacement.
For a no-obligation assessment of whether your cracked driveway suits resurfacing, contact us for a free on-site look.
FAQs
How wide a crack can be filled before resurfacing?
Hairline to about 5 mm wide cracks can typically be filled and resurfaced over, provided the crack is stable. Cracks over 5 mm wide, or any crack with differential height across the edges, should be assessed individually. Wider cracks may indicate sub-base issues that filling alone will not resolve.
Will I see the crack after resurfacing?
If the crack was properly filled and the overlay is applied at sufficient thickness, the filled crack should not be visible through the finished surface. If the crack re-opens due to ongoing movement, it will telegraph back through the overlay. This is why stabilising the crack before resurfacing, not just filling it, matters.
Can hairline cracks in my driveway be left without filling?
Technically yes, but they are better filled before resurfacing. Hairline cracks left unfilled can allow the overlay to bridge the gap thinly. If the concrete moves at all, that thin bridge point is where the overlay will crack first. Filling with flexible caulk takes minutes and reduces that risk.
How long does crack repair add to a resurfacing job?
For hairline and moderate crack repairs on a typical driveway, allow an extra half to full day for filling, cure time and final prep check before the overlay goes down. Structural crack repairs involving injection resin may require a full cure day before the overlay can proceed.
Is there a risk-free way to assess my driveway remotely?
No. Crack assessment genuinely requires an in-person look. A photo can show width and pattern, but cannot show height differential, sub-base condition, hollow spots or the full extent of a crack. Any quote for a cracked driveway should include an on-site inspection.