Old asphalt driveways are common across the Central Coast, particularly in Gosford, Wyong, and suburbs developed in the 1970s, 1990s when asphalt was the standard residential driveway surface. As asphalt ages and fails, homeowners face a decision: remove it and start again, or can something go over the top?
The short answer: new concrete directly over old asphalt is risky and generally not recommended. However, asphalt resurfacing (asphalt over asphalt) and some concrete overlay systems can work under the right conditions. Here’s what you need to know.
Why Asphalt Driveways Are Common on the Central Coast
During the suburban expansion of the 1970s and 1980s, asphalt was cheaper to install than concrete and could be applied faster in large-volume development. Many residential subdivisions around Gosford, Wyong, and Toukley from this era came with asphalt driveways as standard.
Asphalt has a shorter lifespan than concrete, typically 10-20 years before it requires significant maintenance, so much of the region’s 1970s, 1990s asphalt is now at or well past the end of its service life. Cracking, potholing, edge breakdown, and oxidisation (the surface turns dry and grey-brown rather than black) are all common signs of end-of-life asphalt.
Option 1: New Asphalt Over Old Asphalt
Short answer: Yes, this often works if the existing asphalt is structurally sound.
A new asphalt overlay (25-40 mm hot-mix) applied over cleaned, sound existing asphalt is technically straightforward and produces a good result. The requirement is that the existing asphalt:
- Has no significant soft spots or subbase failure (which would cause the new layer to sink and crack)
- Has no heaved areas that would create drainage or level problems
- Is reasonably flat and even (potholes should be patched and levelled first)
When it fails: If the existing asphalt has alligatored cracking (a network of interconnected cracks covering large areas), this indicates subbase failure, and an overlay will simply replicate the same failure pattern within a few years.
Cost: $25 to $55 per m² for asphalt overlay
Option 2: New Concrete Directly Over Existing Asphalt
Short answer: Not recommended and will likely fail within 5-10 years.
The standard advice from concrete engineers is against pouring new concrete directly onto asphalt as a permanent surface because:
1. Bonding is unreliable. Concrete relies on either a bonded or unbonded interface with what’s beneath it. Asphalt is a thermoplastic material, it is slightly flexible and moves with temperature changes. This thermal movement relative to the rigid concrete slab creates shear stresses at the interface that eventually cause the concrete slab to crack and delaminate.
2. Asphalt moisture sensitivity. In the Central Coast’s humid climate, moisture in the asphalt (and asphalt does absorb moisture) will migrate upward into the fresh concrete during curing, potentially affecting the concrete’s water-to-cement ratio and strength.
3. Thickness limitations. A proper concrete driveway slab needs 100-125 mm of concrete on a compacted subbase. If you’re adding 100-125 mm of concrete over existing asphalt, you may create level problems at garage thresholds, footpath transitions, and property boundaries.
4. Joint planning. The control joints (saw cuts) in the new concrete need to be placed correctly for the concrete span, but the existing asphalt below has no control joints that align with the new concrete’s design.
There are situations where contractors do pour concrete over asphalt, typically for commercial areas where a quick and cost-effective solution is needed and longevity expectations are adjusted accordingly. But for residential driveways where a 20-30 year lifespan is expected, concrete over asphalt is not a recommended approach.
Option 3: Concrete Overlay (Resurfacing) Over Existing Asphalt
Short answer: Possible under specific conditions; less common than over concrete substrate.
Polymer-modified cementitious overlays, the type used in standard concrete resurfacing, are sometimes applied over asphalt. The requirements for a successful outcome are more demanding than over concrete:
- The asphalt must be structurally sound (no soft areas, no significant cracking)
- The asphalt must be clean of oil, dust, and loose material
- The asphalt surface must be sufficiently rough and open-textured to provide mechanical key for the overlay
- A specialised primer compatible with asphalt surfaces must be used (not all primers bond to asphalt)
- The overlay thickness must be adequate to provide structural integrity (6-10 mm minimum, rather than the 3-5 mm used over concrete)
When this makes sense: If you have a small asphalt area in good structural condition and want a decorative concrete finish, an overlay is a viable option. The risk is higher than the same overlay over concrete, but skilled applicators with asphalt-compatible products can achieve a durable result.
When this doesn’t work: Large areas with deteriorated asphalt, soft spots, or significant cracking. The overlay will replicate the underlying failure pattern.
Option 4: Remove Asphalt and Pour New Concrete
Short answer: Best long-term outcome; higher upfront cost.
Removing the existing asphalt and starting fresh with a properly prepared subbase and new concrete slab is the approach that delivers the most reliable, longest-lasting result.
Process:
- Machine-remove the existing asphalt (typically done with a skid-steer with cutting attachment or a small milling machine)
- Compact the exposed subbase or add additional road base if needed
- Install formwork and reinforcement
- Pour concrete (100-125 mm, 25-32 MPa)
- Finish and cure
Cost: $120 to $180 per m² including asphalt removal and disposal, subbase preparation, and concrete pour.
This is the most significant upfront investment but the one that delivers the expected 30-40 year service life of concrete.
Asphalt Removal Costs and Challenges
Asphalt removal on residential properties on the Central Coast typically costs $15 to $30 per m² for removal and disposal. The variables:
- Access for machinery: A skid-steer needs a 1.2 m wide access point minimum. For properties where machine access is impossible, asphalt is broken up and removed by hand, significantly more expensive.
- Disposal: Asphalt is a regulated material and must go to a licensed recycling facility. It cannot be disposed of at general waste depots.
- Underlying condition: Occasionally, asphalt removal reveals unexpected conditions beneath, old brick rubble, soft fill, even buried concrete. Remediation adds cost.
Colour and Appearance, Can You Make a Former Asphalt Driveway Look Like Concrete?
Yes. Once asphalt is removed and a new concrete slab poured (or if an overlay over asphalt is used), the surface can be finished and sealed to look like any decorative concrete system, spray-on, stencil, exposed aggregate, or polished.
The appearance of the former substrate has no bearing on the appearance of the final resurfaced product.
Central Coast Specific Considerations
Salt air and asphalt: Asphalt in coastal areas of the Central Coast, particularly within 500 m of the beach at Terrigal, Avoca, Umina, or The Entrance, deteriorates faster than asphalt in sheltered inland locations. Salt air oxidises the bitumen binder, causing the surface to dry out and crack faster. This is one reason many older Central Coast coastal properties are upgrading from asphalt to concrete.
Summer heat: The Central Coast’s summer temperatures (regularly 30°C+) soften asphalt surfaces in direct sun. This is why asphalt driveways on north-facing slopes sometimes develop wheel tracking depressions where vehicles park regularly, the softened asphalt flows slightly under static load. This problem does not occur with concrete or concrete overlays.
Decision Summary Table
| Existing Surface | Condition | Best Option |
|---|---|---|
| Old asphalt | Structurally sound, surface worn | Asphalt overlay or concrete overlay |
| Old asphalt | Soft spots, major cracking | Remove and replace with concrete |
| Old asphalt | Alligatored cracking | Remove and replace, subbase failed |
| Old asphalt | You want a concrete driveway | Remove asphalt, new concrete pour |
| Old asphalt | Budget constrained | Patch and reseal asphalt for now |
Frequently Asked Questions
Can I just seal old asphalt to get a few more years out of it? Yes. Asphalt sealcoating (applying a bitumen emulsion or coal tar product) can extend the life of an otherwise sound asphalt surface by 3-5 years by protecting the binder from UV and water oxidisation. This is a cost-effective holding measure if you plan to eventually replace the driveway but aren’t ready yet.
How do I know if my asphalt’s subbase has failed? Walk the driveway after heavy rain. If sections feel spongy or flex underfoot, the subbase has lost support, likely washed out or softened. Alligatored cracking (interconnected cracks forming a pattern like crocodile skin) is also a strong indicator of subbase failure.
Will new concrete over my old asphalt crack? Almost certainly yes, eventually. The thermal movement of the asphalt beneath the rigid concrete slab creates fatigue stresses. Depending on conditions, cracking may appear within 3-10 years.
Is asphalt or concrete better for the Central Coast climate? Concrete is better suited to the Central Coast’s coastal climate for several reasons: it doesn’t soften in summer heat, it isn’t degraded by salt air the way asphalt binder is, and it has a longer service life. Concrete costs more upfront but has a lower lifetime cost.
How much does it cost to replace an asphalt driveway with concrete on the Central Coast? For a standard residential driveway (40-60 m²): expect $6,000 to $11,000 for removal of asphalt, subbase preparation, concrete pour, and basic finish. See our complete cost guide for a full breakdown.
Not sure what to do with your old asphalt driveway? Get a free on-site assessment, an independent contractor assesses the existing surface, explains your options honestly, and gives you a quote for whichever approach makes the most sense.