How to Install Extruded Curb: Step-by-Step 2026 Guide
Direct Answer (60 words): Extruded curb is installed in a single continuous pour using a self-propelled curb machine that extrudes a low-slump (1 to 2 inch) concrete profile directly onto a compacted base. A two-person crew can place 30 to 50 linear feet per hour. The mix runs 3,500 to 4,000 PSI, the auger feeds the form box, and a hand trowel finishes the cap.
Extruded curb is the production workhorse of commercial parking-lot construction. Unlike a hand-formed pour that needs lumber, stakes, and a screed crew, an extruded curb leaves the machine in its final shape. The trade-off: mix design, base preparation, and operator skill all have to land at the same time. Get one wrong and you get sagging, cracking, or a rough cap that fails the finish inspection.
This guide walks the full install sequence we use on commercial parking-lot work, including a 9,200 linear-foot extruded curb job we placed at a Hood River industrial park in April 2026.
What is extruded curb?
Extruded curb is a continuous concrete profile produced by a self-propelled extrusion machine. The machine carries a hopper, an auger, and an interchangeable form box that shapes the curb cross-section. As the machine moves forward at 30 to 50 linear feet per hour, the auger packs concrete into the form box and the curb emerges fully shaped behind the machine.
Common cross-sections include the 4-inch mountable, the 6-inch barrier, the 6x12-inch full-face, and ribbon curbs at 4x12 inches. The U.S. Department of Transportation's Federal Highway Administration documents extruded curb as an accepted method for low-volume parking facilities and shoulder applications (FHWA Pavement Design Manual).
Why choose extruded curb over hand-formed curb?
Three reasons drive the decision toward extrusion on commercial work:
- Production rate. A two-person crew runs 30 to 50 lf/hr versus 8 to 15 lf/hr hand-formed.
- Material savings. No lumber, no stakes, no form-removal labor.
- Finish consistency. A factory-cut form box delivers the same profile foot after foot.
What tools and materials do you need?
| Item | Spec |
|---|---|
| Curb extrusion machine | Power Curbers 5700-D, Miller M-1500, or Curb Roller Mfg model |
| Concrete mix | 3,500 to 4,000 PSI, 3/8-inch maximum aggregate, 1 to 2 inch slump |
| Form box | Profile-specific (4-inch mountable, 6-inch barrier, etc.) |
| Trowel and edger | 6-inch finishing trowel + 1/2-inch edger |
| String line | Nylon mason's line + steel pins every 25 feet |
| Compaction tester | Nuclear gauge or sand-cone for 95 percent Proctor verification |
How do you prepare the subgrade?
Subgrade prep is where extruded curbs fail or hold for 25 years. The base under the curb must be:
- Compacted to 95 percent of maximum dry density per ASTM D1557. The U.S. Department of Transportation references this benchmark as the floor for parking-lot subgrades (FHWA TS-78-218).
- Trimmed to grade within plus or minus 1/2 inch. A ridged or wavy base produces a curb with the same waviness, since the machine references the existing surface.
- Free of frozen, organic, or saturated material. Oregon's freeze line runs 12 to 18 inches in most service areas, and the Oregon DOT spec (ODOT Standard Specifications, Section 00759) requires removal of unsuitable subgrade before placement.
On the Hood River industrial-park job, we ran a 6-inch crushed-aggregate base over native sandy loam, compacted in two 3-inch lifts. We tested every 100 feet with a nuclear gauge.
How do you set the line and grade?
The string line drives the entire pour. Set steel pins every 25 feet along the planned face of the curb. Pull a nylon mason's line tight at the design top-of-curb elevation. The machine's sensor wand rides this string and steers the form box laterally and vertically.
Tolerances per ODOT 00759:
- Surface tolerance: 1/4 inch in 10 feet
- Alignment tolerance: 1/2 inch from the design line
- Vertical tolerance: 1/4 inch from the design grade
What mix design produces a clean extruded curb?
Extruded curb mix is unforgiving. Slump that is too wet sags the cap. Slump that is too dry chokes the auger and produces tearing on the face.
| Mix Property | Spec |
|---|---|
| Compressive strength | 3,500 to 4,000 PSI at 28 days |
| Slump | 1 to 2 inches (low-slump) |
| Maximum aggregate | 3/8 inch |
| Air entrainment | 5 to 7 percent (Oregon freeze-thaw) |
| Cement content | 564 to 658 lb/cy (6 to 7 sacks) |
How do you operate the machine through the pour?
- Position the machine at the start station, form box at design grade.
- Charge the hopper. The truck operator backs in and discharges 1/2 to 1 cy at a time.
- Engage the drive. The machine creeps forward at 30 to 50 lf/hr.
- Monitor the cap behind the machine. A trailing finisher walks behind, broom-finishing the top and edging the front face.
- Stop at expansion joints. Tool a 1/2-inch joint every 10 to 15 feet per the American Concrete Pavement Association (ACPA Section 5).
How do you finish and cure the curb?
Finishing happens in real time as the curb emerges:
- Strike the top. A 6-inch trowel skims the cap to remove machine ridges.
- Edge the face. A 1/2-inch edger rounds the top corner.
- Broom-finish. A medium broom passes laterally for traction.
- Tool joints. Cut control joints every 10 feet, expansion joints every 30 feet with a 1/2-inch preformed filler.
Cure with a sprayed-on curing compound (ASTM C309 Type 2) or wet burlap for 7 days. The U.S. EPA's Stormwater Best Management Practice publications note that curing affects long-term durability and stormwater performance of curb-and-gutter systems (EPA NPDES).
How much does extruded curb installation cost?
Industry Baseline Range
| Component | Range |
|---|---|
| Extruded curb installed (commercial) | $8 to $14 per linear foot |
| Subgrade prep (if separate) | $2 to $5 per linear foot |
| Mobilization | $400 to $1,200 per project |
| Sawcut existing pavement | $4 to $7 per linear foot |
Current Market Reality
Oregon 2026 market rates run higher than baseline because diesel costs, ready-mix freight surcharges, and CCB-licensed crew wages have all climbed. Add 10 to 25 percent on small parking-lot pours under 500 linear feet, where mobilization costs dilute production efficiency.
What does a real install look like?
In April 2026 we extruded 9,200 linear feet of 6-inch barrier curb at a Hood River industrial park. A two-person crew with a Power Curbers 5700-D finished placement in 22 production hours over four days. The 6-inch crushed base was compacted to 96 percent Proctor, and we tooled control joints every 12 feet and expansion joints every 36 feet. The owner accepted the work with zero rework on a 1/4-inch tolerance check.
Frequently Asked Questions
How many linear feet of extruded curb can one machine pour per day? A trained two-person crew on a Power Curbers 5700-D pours 200 to 400 linear feet in a typical 8-hour day on commercial parking-lot work, depending on truck-cycle time and complexity of curves and ramps.
Does extruded curb need rebar? Plain extruded curb under a 6-inch face does not need rebar in most parking-lot applications. The American Concrete Institute (ACI 318) treats it as plain concrete reinforced by aggregate interlock. Heavy-duty industrial barrier curbs at 8 inches or higher should include #4 continuous rebar.
Can extruded curb be placed in cold weather? Yes, but air temperature must be above 40 degrees F at placement and rising. Heated water or accelerator admixtures are typical for placements between 40 and 50 degrees F. Below 40 degrees F, follow ACI 306 cold-weather concreting protocols.
How long until you can drive on extruded curb? Vehicles can pass the curb at 24 hours when the cap reaches finger-pressure resistance. Full design strength is reached at 28 days. Avoid lateral impact from snowplows or construction traffic during the first 7 days.
What tolerance does Oregon DOT allow for extruded curb? Oregon DOT Standard Specification 00759 allows a surface tolerance of 1/4 inch in 10 feet and an alignment tolerance of 1/2 inch from the design line for commercial extruded curb sections.
We extrude commercial parking-lot curb across the I-5 corridor and Central Oregon. To plan your project, start with our concrete curb guide, compare machine choices in our best extruded curb machines review, or get a quote on curbing in Portland Oregon.