Mountable Curb vs Barrier Curb: Which Is Right for Your Lot?

Mountable curb (4 inches face, sloped top) is the right choice for fire lanes, drive-thru islands, and emergency-access routes where vehicles must occasionally cross the curb at low speed. Barrier curb (6 to 8 inches face, vertical or near-vertical top) is the right choice for pedestrian protection, perimeter definition, and any location where vehicles must be physically stopped. The American Association of State Highway and Transportation Officials (AASHTO Green Book A Policy on Geometric Design of Highways and Streets) Figure 4-2 illustrates the geometric distinction; the Oregon Standard Specification 00759 carries both profiles as standard pay items.

This article gives you the side-by-side specs, the four use-case decision points, and the ADA implications that often determine the answer.

Quick Verdict: Mountable vs Barrier

Current Market Reality

Pricing for both profiles tracks closely because they use the same 4,000 PSI mix and the same crew. The 4-inch mountable section uses slightly less concrete per linear foot, but the wider 12-inch top requires more formwork or a larger slipform shoe, which roughly cancels the material savings.

What Is Mountable Curb?

Mountable curb (sometimes called "rollover curb") has a 4-inch face and a 12-inch top sloped at roughly 1:3 (rise:run). The slope lets a passenger vehicle's tire roll up and over the curb at speeds under 10 mph without sidewall damage or chassis contact. A fire apparatus at idle pace can mount the curb and continue without the operator needing to slow further.

The Federal Highway Administration (FHWA Roadside Design Guide) classifies mountable curb as a "non-redirective" element — it does not contain or redirect a vehicle. That is the entire design intent.

Common applications:

• Fire lanes — Oregon State Fire Marshal allows mountable curb to define a fire lane without obstructing apparatus access
• Drive-thru islands — passenger vehicles can mount during high-volume queue overflow
• Emergency-access routes — designated EVA routes through landscape areas
• Drive aisles in heavy-truck environments — backing trucks can clip the curb without tearing landscaping
• HOA shared driveways — residential turnouts where occasional vehicle override is expected

What Is Barrier Curb?

Barrier curb has a 6 to 8 inch face and a 6-inch flat top with a near-vertical front face (1:6 maximum batter per AASHTO). The geometry is the design: at 6 inches, a passenger-car tire cannot mount the curb at parking-aisle speeds. The vehicle stops at the line.

The 8-inch heavy-duty version is specified for truck courts, dock aprons, and warehouse perimeters under AASHTO H-20 truck loading. Above 8 inches, the curb starts to be reclassified as a low retaining wall and triggers different structural review under ACI 318 Building Code Requirements for Structural Concrete.

Common applications:

• Storefront perimeters — pedestrian protection along retail frontage
• Parking-stall protection — at the head of angled stalls to prevent overshoot
• Landscape island borders — protects irrigation, lighting, and plantings
• Property-line definition — adjacent to public right-of-way
• Loading-dock aprons — 8-inch heavy-duty version

ADA Implications

The Americans with Disabilities Act treats the two profiles differently. Per ADA Standards Section 405:

• Barrier curb must have a curb ramp at every accessible-route crossing. The ramp is 1:12 maximum running slope, 36 inches minimum width, with a detectable warning surface at the base.
• Mountable curb at 4 inches still triggers the ramp requirement on accessible routes because ADA defines a "level change" as anything over 1/4 inch. The ramp can be a less aggressive geometry (the curb is already partially sloped), but a flush-grade transition is still required at the accessible route.

This is the most common spec mistake on commercial sites: assuming mountable curb removes the ADA ramp requirement. It does not.

When Mountable Curb Earns Its Spot

Spec mountable curb when one of these applies:

• A fire lane is the primary function. Oregon SFM accepts mountable curb to delineate fire-access lanes without blocking apparatus access.
• Drive-thru queue overflow needs to spill onto the median. Mountable curb prevents tire damage when vehicles cut the inside corner.
• Heavy trucks regularly back across the curb. Distribution centers, loading docks, and dock aprons benefit from the forgiveness of the mountable profile.
• Snow plowing is on a shared maintenance contract. Mountable curb survives plow-blade impact better than vertical barrier curb.

On a 12,000 square foot Beaverton drive-thru restaurant we curbed in January 2026, we specified 4-inch mountable curb on the inside of the drive-thru lane (180 LF) plus 6-inch barrier curb at the parking-stall heads (110 LF) and storefront frontage (140 LF). The mountable section let delivery box trucks back into the dumpster pad without tearing landscaping; the barrier section protected pedestrians at the storefront. See related guidance in our best curb for drive-thru lane breakdown.

When Barrier Curb Is the Right Call

Reach for barrier curb in these conditions:

• Pedestrians walk adjacent to the curb. 6 inches is the minimum face for vehicle deterrence at parking-aisle speeds.
• You need a visible property line or perimeter. Barrier curb is the legal boundary on most commercial sites.
• Truck or trailer impact is expected. 8-inch heavy-duty barrier curb handles AASHTO H-20 loading.
• Landscape protection is a priority. Vehicles can't mount and crush plantings or irrigation.

For more on profile selection across the full curb family see our concrete curb buyer's guide, and for residential rollover-curb context see rolled curb vs barrier curb. When the curb is part of a paving rebuild, our asphalt paving services crew sequences both pours.

Get the Right Profile for Your Lot

Most commercial parking lots use both profiles — barrier curb for the pedestrian-facing perimeter, mountable curb for fire lanes and drive-thru islands. The right blend depends on the site plan, the fire-marshal review, and the ADA accessible route layout.

Get a custom quote and we'll walk your site to map the curb-by-section spec before pour day.