What Is Chip Sealing?
Chip sealing (also called chip seal or tar-and-chip paving) is a pavement surface treatment that bonds a layer of crushed stone aggregate into a sprayed asphalt emulsion. The result is a textured, durable surface that protects the underlying pavement from UV damage, water infiltration, and wear. It's widely used on rural roads, low-traffic driveways, and as an economical alternative to full asphalt overlays when the existing base structure is sound.
Is Chip Seal the Same as Asphalt?
No — chip seal and asphalt are different products. Asphalt pavement is a full-depth layer of hot-mix material laid and compacted to form a load-bearing surface. Chip seal is a surface treatment applied over existing pavement — it protects what's already there but doesn't add structural strength. Think of asphalt as the foundation and chip seal as a high-durability protective coating with embedded aggregate.
The Technical Breakdown: How Chip Seal Pavement Works
Chip sealing has been used on road surfaces for over a century — it's proven, well-understood technology. Understanding the mechanics helps you know when it's the right tool and when it isn't.
The Materials
Asphalt emulsion binder: The liquid base is asphalt emulsion — asphalt cement mixed with water and an emulsifying agent to make it sprayable at lower temperatures. When the emulsion breaks (water evaporates), it bonds aggressively to the existing pavement and grabs the aggregate. Different emulsion grades are used depending on climate, traffic, and surface condition.
Aggregate chips: The chips are crushed stone — typically granite, limestone, or basalt — sized to a specific gradation. Common chip sizes range from 3/8 inch to 3/4 inch. The aggregate needs to be clean, angular, and within a tight size range for even embedment. In the Central Valley, granite is a common choice due to local availability and hardness.
The Application Process Step by Step
Step one: surface preparation. Cracks wider than 1/4 inch get filled. Oil-contaminated areas get treated. Skipping prep is the most common reason chip seal fails prematurely.
Step two: the emulsion distributor truck sprays a uniform coat of hot liquid binder at a controlled rate — typically 0.25 to 0.35 gallons per square yard. Too much binder and the chips float; too little and adhesion is poor.
Step three: aggregate spreader follows immediately, spreading chips at a controlled rate in one even layer.
Step four: a pneumatic tire roller makes multiple passes to embed the aggregate into the binder. Pneumatic tires seat the chips without crushing them.
Step five: the emulsion breaks as water evaporates, locking the aggregate in place. Loose chips are swept off after curing. Our full paving services team handles the complete process from prep through final sweep.
Single vs. Double Chip Seal
A single chip seal applies one binder layer and one aggregate layer. A double chip seal repeats the process — creating a thicker, more durable surface. Double chip seal is used on higher-traffic roads and surfaces needing more protection depth. Most residential driveways use single; rural road work often specifies double.
When Chip Seal Is — and Isn't — the Right Answer
Chip seal works when the existing base is structurally sound, you need surface protection without a full overlay cost, and the surface is low-to-moderate traffic. It doesn't work when the base has failed, there's significant structural cracking, or heavy trucks will use the surface immediately after application.
Our asphalt services in Fresno include both chip seal and full overlay options. We'll tell you which one your pavement actually needs. Check our Central Valley service area and request a free evaluation.
Frequently Asked Questions About Chip Sealing
What's the difference between chip seal and tar-and-chip?
Chip seal and tar-and-chip are the same process — different regional terms for identical technology. "Tar-and-chip" is older terminology and technically a misnomer since modern applications use asphalt emulsion rather than coal tar. "Chip seal" is the current industry-standard term. You may also hear aggregate seal, surface dressing, or seal coat with aggregate — all the same basic process of bonding crushed aggregate into a sprayed binder.
Can chip seal be applied over old, cracked asphalt?
It depends on the cracking. Surface checking, minor oxidation cracking, and hairline cracks can be treated before chip sealing without issue. Structural cracking — alligator cracking, edge failures, base failure — means the pavement can't support a surface treatment. Applying chip seal over structural failures delays the inevitable and wastes your money. A site visit before any quote is non-negotiable for a reason — this distinction has to be made in person.
How is chip seal used on public roads versus private driveways?
Chip seal is one of the most widely used surface treatments on rural and low-volume public roads across California — county roads, farm roads, and secondary highways. The application is identical to residential use but at larger scale with formal specification compliance. Private driveway chip seal follows the same technical principles but allows more flexibility in material choices and doesn't require the formal testing documentation that public work demands.
Does chip seal need maintenance after application?
Chip seal is relatively low-maintenance. The aggregate layer handles the UV protection that seal coating does on standard asphalt. A retreatment — new emulsion and aggregate over the existing surface — is typically done every 7–10 years. Crack filling is still important if cracks develop through the chip seal into the underlying pavement. The maintenance cycle is less frequent than standard asphalt sealing, which is part of the appeal for rural property owners.
Is chip seal slippery when wet?
The opposite — chip seal provides better wet-weather traction than smooth asphalt because the aggregate texture creates more contact between tires and pavement. This is one reason it's preferred on rural roads with curves and grades. Immediately after application, during the initial loose-chip period, there can be variability in traction. Once cured and excess chips cleared, the embedded aggregate provides excellent skid resistance.