Commercial Property Paving: Hot Mix Asphalt Specifications for Parking Lots

Commercial Property Services

Not all asphalt is the same — understanding the specifications that differentiate a long-lived commercial parking lot from a premature failure helps owners evaluate contractor proposals.

Surface course aggregate size determines finish texture and durability. A 12.5 mm (Superpave SP-12.5) mix is the standard specification for Ontario parking lot surface courses — fine enough to produce a smooth, safe surface but coarse enough for adequate durability under vehicle loads.

Key Considerations

Binder course specifications: most commercial parking lots use a two-layer construction: a granular base, a binder course asphalt layer (typically 50 mm of SP-19 mix), and a surface course (typically 40 mm of SP-12.5 mix). The binder course provides structural capacity; the surface course provides the wearing surface.

Compaction is the most important quality variable in asphalt placement. Under-compacted asphalt has lower density, higher air void content, and dramatically lower durability than properly compacted material. OPSS (Ontario Provincial Standard Specification) requires compaction to a minimum 92 to 97% of Marshall density depending on layer position.

Working With D&D Commercial

Tack coat between layers ensures bonding between the binder course and surface course. Tack coat is a diluted asphalt emulsion applied to the lower course surface before the upper course is placed. Without tack coat, the courses may de-bond under traffic loading, leading to delamination failure.

Mix temperature at placement matters: hot mix asphalt must be placed and compacted before it cools to approximately 85°C. Placement temperature requirements mean that long hauls from the plant, cold weather, or slow placement can result in undersized placement windows and inadequate compaction. Request QCQA (quality control / quality assurance) documentation for any paving project.