Exposed aggregate driveways look fantastic when they're fresh — all those stones gleaming in the sun — but UV exposure, rain, and traffic gradually dull the surface and wash out the sealer. The good news is that with a weekend's work, the right products, and a bit of elbow grease, you can bring most faded exposed aggregate driveways back to life without calling in a contractor.
Understanding Why Exposed Aggregate Fades
The colour and sheen of an exposed aggregate driveway comes largely from the clear or tinted sealer applied over the surface, not the concrete itself. Over time — typically every 3–5 years in New Zealand conditions — UV radiation breaks down the sealer, causing it to turn white (a process called blushing or milking), peel, or simply wear away. Once the sealer is gone, the aggregate stones lose their wet, rich look and the surface becomes more porous and prone to staining.
NZ's variable climate plays a role too. In wetter regions like Auckland or the West Coast, moss and algae growth can add a green tinge to the surface, while in sunnier areas like Hawke's Bay or Nelson, UV degradation tends to be the bigger culprit.
What You'll Need
- Pressure washer (minimum 2,000 PSI / 140 bar recommended for concrete)
- Stiff-bristle broom or deck brush
- Concrete cleaner/degreaser (available at Bunnings or Mitre 10)
- Concrete sealer — solvent-based or water-based, clear or tinted (more on this below)
- Paint roller with an extension pole, or a pump-up garden sprayer
- Safety glasses, gloves, and old clothing
- Crack filler or concrete patching compound for any repairs
Step 1 — Clear and Degrease the Surface
Remove all vehicles, pots, and furniture. Sweep away loose debris. Apply a concrete degreaser to any oil or grease stains and scrub with a stiff brush before rinsing. Oil contamination will prevent sealer from bonding properly, so don't skip this step.
Step 2 — Pressure Wash Thoroughly
This is the most important step. Use a fan-tip nozzle (25–40°) and work methodically in overlapping passes. Hold the wand about 200–300 mm from the surface — too close and you risk dislodging aggregate or etching the concrete. For moss, lichen, or algae, a diluted sodium hypochlorite (bleach) solution or a dedicated concrete moss killer applied before pressure washing will help. Always rinse thoroughly after using any chemical treatment.
Allow the driveway to dry completely — typically 24–48 hours in fine weather. Applying sealer to damp concrete is one of the most common causes of sealer failure.
Step 3 — Repair Cracks and Damaged Areas
Inspect the surface for cracks, spalling, or loose aggregate. Small cracks (under 3 mm wide) can be filled with a flexible concrete crack filler. Larger structural cracks may indicate a deeper problem with the sub-base and are worth having assessed by a professional driveway layer. Products from Sika or Ardex are well regarded for concrete repairs in NZ.
Step 4 — Choose the Right Sealer
Sealer selection matters. The two main types are:
| Type | Pros | Cons |
|---|---|---|
| Solvent-based (xylene/aromatic) | Deep penetration, rich wet look, durable | Strong fumes, flammable, harder to apply |
| Water-based (acrylic) | Low odour, easier cleanup, eco-friendlier | May not penetrate as deeply, less sheen |
For a classic wet look that makes aggregate colours pop, solvent-based sealers are traditionally preferred by professionals. However, water-based technology has improved significantly and is a practical choice for DIYers. Check with your local PlaceMakers or concrete supply store for products suited to your region's conditions.
Important: If you're using a solvent-based sealer, ensure excellent ventilation, keep ignition sources well away, and wear a respirator rated for organic vapours. Check WorkSafe NZ guidance on safe handling of solvents.
Step 5 — Apply the Sealer
Apply sealer in thin, even coats — two thin coats are far better than one thick coat. A thick application traps air and causes the sealer to blister or turn white. Use a roller or low-pressure sprayer and work in sections, maintaining a wet edge to avoid lap marks. Apply the second coat once the first is touch-dry (check the manufacturer's datasheet for timing — typically 1–4 hours).
Keep foot traffic off for at least 24 hours and vehicles off for 48–72 hours, or as directed by the product instructions.
Ongoing Maintenance Tips
- Reseal every 3–5 years, or sooner if water stops beading on the surface.
- Clean up oil spills promptly — they degrade sealer and stain aggregate.
- Avoid using metal shovels or harsh de-icing salts, which can damage the surface.
- A light wash with a garden hose and broom a few times a year keeps moss and grime at bay.
For more guidance on durable building surfaces in NZ conditions, BRANZ publishes useful research and technical notes.
When to Call a Professional
Some situations are best left to an experienced driveway layer:
- Widespread cracking or heaving — this usually signals sub-base failure and may require sections to be broken out and re-laid.
- Delaminating or peeling sealer over a large area — old sealer may need to be chemically stripped or mechanically ground back before resealing, which requires specialist equipment.
- Significant aggregate loss — once the surface profile is compromised, a professional can assess whether resurfacing or full replacement is needed.
- New driveway construction — building consent requirements vary by council. Some driveways near boundaries or with significant earthworks may require consent under the NZ Building Code. Always check with your local council.
You can find qualified, local driveway layers and concreters on tradedirectory.co.nz.
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