What Is RMS Specification?

Roads and Maritime Services (now part of Transport for NSW) publishes a suite of technical specifications governing the construction and maintenance of roads in NSW. When a contractor says they work to "RMS spec," they mean their materials, construction methods, and quality control processes comply with these standards.

The most relevant specifications for asphalt and civil work include:

  • QA Specification R116 - Asphalt Wearing Course
  • QA Specification R118 - Dense Graded Asphalt
  • QA Specification R142 - Sprayed Bituminous Surfacing
  • QA Specification R67 - Roadbase and Subbase

These specifications govern everything from the source and grading of aggregates, to binder content, mixing temperatures, compaction requirements, and defect tolerances.

Why Does It Matter for Private Projects?

RMS specification is mandatory for state and local government road work, but it matters for private projects for a different reason: it's a quality benchmark that has been extensively tested and refined over decades.

A contractor who routinely works to RMS spec on council contracts has supply chains, equipment, and quality control processes calibrated to meet a demanding standard. That same standard applies when they build your driveway or commercial carpark, even when it's not contractually required.

A contractor who doesn't work to RMS spec on government contracts - because they're not approved or can't meet the requirements - is likely operating to a lower standard across all their work.

Asphalt Mix Design Under RMS Specification

RMS specifications define specific requirements for asphalt mix design, including:

Aggregate Size and Grading

The specification number (AC10, AC14, AC20) refers to the maximum aggregate size in millimetres. AC10 is typically used for residential driveways and light commercial work. AC14 and AC20 are used for heavier traffic environments. Each has a defined grading envelope that the combined aggregates must fall within.

Binder Content and Grade

The bitumen binder percentage is specified within a range (typically 5.0% to 6.5% by mass of mix, depending on aggregate type). The binder grade is selected to suit the climate - a softer grade for cooler climates, a stiffer grade for hot environments like western NSW. Central Coast work typically uses a C320 or C450 grade.

Mixing and Laying Temperature

Mix temperature at the plant and at the point of laying are specified. Asphalt laid below minimum temperature doesn't compact properly and fails early. This is a common cause of quality issues when contractors stretch material over longer haul distances than appropriate.

Compaction Requirements

RMS specifications require compaction to be tested using a nuclear density gauge. Minimum relative density is specified (typically 97% of theoretical maximum density for wearing course). This is not a visual check - it's a measured result.

Contractors working to RMS spec carry density gauges and test compaction as a matter of standard practice. Contractors who don't carry testing equipment are guessing at their compaction level, which means they're guessing at whether the job will last.

What to Ask a Contractor About Their RMS Accreditation

If RMS specification matters to your project (council work, heritage roads, any project with a formal specification requirement), ask the contractor:

  • Are you an approved contractor with Transport for NSW? For what work categories?
  • Do you carry and use a nuclear density gauge on site?
  • Do you use approved asphalt plants with current mix design approvals?
  • Can you provide compaction test records from previous projects?

Brisbane Water Bitumen has been a council panel contractor building to RMS specification on the Central Coast for over 20 years. We apply the same material and compaction standards to private projects that we meet on government contracts.