Unsealed road maintenance

Establishing a ‘well bound’ surface

Council uses local gravel sources and a good binding material to lay unsealed roads.

When the binding material gets wet, the road may look ‘slushy.’ This is normal for a good binding material.

Grading works

Grading works is when a grader (a road maintenance machine) restores the road shape (its camber and cross-fall) by redistributing gravel. Sometimes a roller is used afterwards to compact the bound surface.

Preventing gravel loss

Council must balance the need to reshape the road with how often it is done, because graders damage the existing gravel by breaking down the stones.

Councill aims to:

• control the frequency of grading works to extend the life of the gravel
• recover gravel that has been pushed out of the wheel tracks by vehicles
• lay new gravel when needed

Recovering gravel from the side of the road means that clumps of grass can often be seen on the road after grading works. These grass clumps do not affect the safety or function of the road.

Fun fact: Studies of unsealed road gravel show an average of 16mm – 22mm per annum of gravel loss.

Common problems on unsealed roads

Potholes

Potholes usually form when the weather is wet and water has softened the road. As vehicles drive over the road, the impact and tyre action displaces the softened gravel. 

Preventing potholes

Council undertakes grading works to reduce the occurrence of potholes. Maintaining the shape and slope of the road surface (such as the camber and cross-fall), ensures better drainage during wet weather.

Potholes are regularly filled with gravel, with focus placed on restoring shape for prevention when the next grading work is carried out.

Fun fact: A pothole is a sign that the road has a good gravel base (not to be confused with a failure where no gravel exists and mud is blowing out).

Corrugations

Corrugations look like ripples on the road surface. They form when vehicles bounce on the road and push loose materials into small dips and crests. This occurs more on hills and around tight corners.

Preventing corrugations

Councill specifically uses local gravels that have better ability to bind together and not corrugate as quickly. Controlling the frequency of grading works also reduces corrugations on the road.

Fun fact: Even sealed roads can have corrugations, particularly in tight steep corners.

Dust nuisance

Unsealed roads are constantly exposed to the natural forces of rain, wind and sun. When the weather is dry, traffic on unsealed roads creates dust.  This can be a nuisance for nearby residents and create dust clouds that briefly affect visibility to passing vehicles.

Preventing dust nuisance

Councill specifically uses local gravels that have better ability to bind together and thereby generate less dust. Controlling the frequency of grading works (which loosens the road’s surface) also reduces dust.

Upgrading to a sealed road

Unsealed roads can cause problems for homeowners living along those roads, mainly due to the dust generated by vehicles that use the road. For this reason, Council is often approached by members of the community requesting that specific roads are sealed.

Funding road sealing

The New Zealand Transport Agency Waka Kotahi may subsidise seal extensions, but historically the seal extensions sought by our community have not met the set eligibility criteria.

When NZTA funding is not available, seal extensions are paid for by councils and their rate payers.

Waikato District Council’s Long Term Plan currently has no specific funding towards the sealing of unsealed roads. Communities and private developers can engage with Council through the Long Term Plan to seek funding.

NZTA subsidy

To see the eligibility criteria for NZTA funding, read the general circular about the investment assessment process for Road Maintenance Activity Classes.