Bituminous materials are binders made from bitumen, the heavy residue of petroleum refining, or from coal tar, and they are the basis of asphalt pavement, sealcoats, and many waterproofing products.
In parking, bituminous materials are most visible as the asphalt surface of a surface lot: aggregate held together by an asphalt binder, laid hot, and compacted. They also appear in crack fillers, sealcoats, and modified bitumen membranes used under plaza decks and on roofs.
In surface lots
- Asphalt offers the lowest first cost of any durable parking surface, but it ages steadily. Sun and oxygen harden the binder, water enters through cracks, and freeze and thaw cycles widen them.
- The usual maintenance ladder is crack sealing, then sealcoat, then mill and overlay, and finally full reconstruction once the base has failed.
- Coal tar sealcoats, once common, are now restricted in several states and cities because of their environmental profile, so asphalt-based sealers are the default.
In structured parking
- Asphalt is rarely used as the wearing surface on an elevated concrete deck. It adds dead load, can hold water against the slab, and hides cracking and corrosion from the condition surveys that a garage depends on.
- Structured decks are more often protected with sealers and traffic-bearing membranes.
The Parkonomics view
A surface lot’s pavement is a capital liability that rarely appears in the operating budget until it fails. Owners who schedule crack sealing and sealcoating spend far less than those who wait for reconstruction, and for lots held for future development, the right strategy is often the opposite: keep the surface safe and serviceable, and spend nothing that the next building will tear up.
Related terms: Albedo, Foundation Systems, Heat Island Effect, Life Cycle Cost
Further reading: The Evolution of U.S. Parking Structures in 2026