Asphalt Curb and Berm: How Extruded Curbing Works and How Many Tons

An asphalt curb is a continuous ridge of hot mix formed on top of finished pavement by a curb machine. It channels water, keeps cars off lawns and planting beds, and gives a clean edge to parking lots and driveways. A low, rounded or sloped version is often called an asphalt berm. Both are cheaper and faster to install than concrete or stone curbing, but they're also more easily damaged.

How many tons calculator → Driveway edging ideas →

How Asphalt Curb Is Made

A curb machine, sometimes called an extruder or curber, is a compact self-propelled machine with a hopper, an auger, and a shaped mold. Crews feed it hot mix, often a finer surface mix, and the auger pushes the material out through the mold while the machine creeps forward. The pressure compacts the mix into the curb shape as it goes. Many crews apply a tack coat or asphalt adhesive to the pavement first so the curb bonds to the surface instead of sliding off.

Some small jobs are formed by hand with a rake, tamper, and a shaping tool, but machine-formed curb is denser and more consistent.

Common Shapes

Shape	Look	Typical use
Sloped or mountable berm	Low, angled face; cars can roll over it	Road shoulders, driveway edges, water control
Rounded berm	Soft, rolled top	Residential edges, lawns
Vertical-face curb	Steeper face, more barrier-like	Parking lot islands and perimeters
Wedge or speed hump-style profiles	Specialized molds	Directing flow or traffic

Exact dimensions depend on the mold. Ask your contractor for the profile's height and base width, since that controls material and cost.

Where Asphalt Curb Works Well

• Directing runoff along a driveway or lot edge toward a drain or swale
• Protecting edges of pavement next to soft shoulders
• Keeping vehicles off landscaping in parking lots
• Budget projects where concrete curb isn't affordable

For driveway water problems, see asphalt driveway drainage.

Asphalt Curb vs. Concrete and Stone

Factor	Asphalt curb	Concrete or granite curb
Upfront cost	Lower	Higher
Install speed	Fast; goes on after paving	Slower; forms or setting required
Durability	Can chip or break from plows and tires	Much more resistant
Repair	Easy to patch or re-extrude	Harder; sections replaced
Looks	Matches the pavement	Distinct edge

Snowplows are asphalt curb's biggest enemy. Marking curb lines with stakes before winter helps drivers avoid them.

Tonnage Math by Length

Curb tonnage comes from the cross-section area times length. Here's an illustration with a trapezoid profile 6 inches tall, 8 inches wide at the base, and 4 inches wide at the top:

1. Cross-section: ((8 + 4) ÷ 2) × 6 = 36 square inches
2. In square feet: 36 ÷ 144 = 0.25 square feet
3. Per 100 feet: 0.25 × 100 = 25 cubic feet
4. Weight: 25 × 145 = 3,625 pounds, or about 1.8 tons per 100 feet

A smaller berm, say 4 inches tall, 10 inches wide at the base, and 2 inches at the top, is ((10 + 2) ÷ 2) × 4 = 24 square inches, or about 1.2 tons per 100 feet. Add a little for waste and startup. Extruded curb is compacted by the machine, so actual density depends on the mix and the machine; the 145 pounds per cubic foot figure is a planning value. The tonnage calculator handles the paving itself.

Installation Tips

• Install on clean, dry pavement, ideally soon after paving while the surface is fresh.
• Use tack coat or adhesive so the curb bonds. See tack coat.
• Lay out the line with paint or string before the machine arrives.
• Leave gaps or flumes where water needs to exit.
• Keep traffic off until the curb cools and hardens.

Repairing Damaged Curb

Small chips can be patched with hot mix or a quality cold patch, compacted and shaped by hand. Long broken runs are usually cut out and re-extruded. If the pavement edge itself is crumbling, see driveway edge repair.

Asphalt Curb Cost Factors

Contractors usually price extruded curb by the linear foot, and the rate depends on the profile size, total footage, how much hand work the corners and islands need, and whether it's installed during a paving job or as a separate trip. A separate mobilization for a short run can cost nearly as much as a longer one, so it often pays to add curb while the paving crew and hot mix are already on site. Ask for the profile dimensions in writing so bids compare the same product, and get local quotes.

Bottom Line on Asphalt Curb

Asphalt curb and berm are hot mix extruded into a shape on top of pavement to guide water and mark edges. They're affordable and quick but less tough than concrete, especially against plows. Estimate tons from the profile's cross-section and length, and bond the curb with tack coat.