Types of road seals

We use two materials to surface a road: chipseal and asphalt.

Asphaltic concrete (asphalt) and chipseal are the two surfacing options most commonly used on our roads.

Read more about why we resurface roads, and how we decide which option to use.

Differences between chipseal and asphalt  

Structural improvement: Asphalt provides structural benefits to the road which chipseals can’t. Asphalt is a paved layer where chipseal is a surface coating. 

Rideability of the road: Asphalt improves the levels of the road providing a smoother ride quality to the road users. Because chipseal is a surface coating it has very little influence on the levels of the road surface. 

Watertightness: Asphalt is quite sponge like when applied in the thicknesses required for our flexible pavements in the Wellington area. Chipseal is a great water proofer and is critical to the survival of our roads. 

Texture of final surface: Most asphalts used in Wellington have a smooth surface. Chipseal has a textured surface that can vary from only marginally rougher than asphalt to extremely coarse, depending on the need. 

Skid resistance and safety: Asphalt has lower skid resistance than Chipseal. Thus, chipseal is safer from a vehicle breaking perspective. Good to have a chipseal on the approach to a pedestrian crossing for example. 

Environmental impact: Asphalt uses a lot more aggregate and bitumen than chipseal. Depending on the thickness of the asphalt this can vary anywhere from four times to twenty times. Chipseal is thus significantly more environmentally friendly and has a much lower carbon footprint. 

Life expectancy: Asphalt between 10 and 20 years depending on the traffic loading. Chipseal between 8 and 15 years depending on traffic loading. 

Cost: Asphalt uses a significant amount more aggregates and bitumen than chipsealing. Thus, it is any considerably more expensive, generally around four times more than chipseal. 

Aftercare: Asphalts have very little to no aftercare. Chipseal takes a time to embed and cure. There will be loose stones on the road for the first few weeks. This is managed by increased sweeping intervals.

Caring for chipseal

Chipseal uses bitumen, a waterproof substance that keeps roads dry once it has had time to cure and become attached to the road surface. When chipseal is fresh, or on hotter days, this bitumen is softer, meaning that it can be exposed if the layer of stone chips is disturbed. 

To reduce sticky residue on new chipseal, or during a summer scorcher, follow these tips:

  • Avoid accelerating hard or braking heavily. Stopping or starting quickly creates more friction on the road, which can disrupt the stone layers over the bitumen, exposing it to the air.
  • Keep your vehicle in motion while turning the wheels. This is not always possible due to traffic and confined parking spaces, but if you can keep moving while you turn, it will cut down on disrupting the road surface. You can spot surface disruption by looking for circular shaped black spots on the area where the wheels are turned.
  • Apply some sand to the surface. If you're finding some trouble spots in front of your driveway or around on-street parking near your house, putting down some beach sand might help. You can also let us know if your street needs some attention by getting in contact with us.

The seal will settle down once the road has had a chance to cure, or when the weather cools down.