How Tall Should a Curb Be Above the Grass?

Roadside Curbing

• Specifications for roadside curbing may vary among jurisdictions across the United States. Regardless of the code-directed guidelines for height of curb or materials used alongside a road, the soil needs to meet the top of the curb on the adjacent field or lawn. Grass should not be lower than the curb alongside a roadway. This creates a safety hazard for walking, as tripping occurs when the lawn or soil is below the top of the curb. The soil should be flush or no lower than 1/2 to 1 inch from the curb's top.

Edging

• Concrete paver blocks or bricks may also be used as a curb edging to define and contain garden beds. Safety is a primary concern even for garden edging. You want the edging to be at a height flush with the lawn, or obviously much higher so the edging is very visible and not a tripping hazard. Ideally, a flush-level edging curb adjacent to the lawn allows the lawnmower wheels to roll atop the curb. Too low of a curb causes the lawnmower's cutting blade to taper downward and scalp the grass. Too high of a curb doesn't allow the blade to evenly cut the lawn, resulting in grass that is taller next to the curb. Garden bed edging is most visible if it rises at least 2 inches above the height of the lawn after mowing. If that's impractical or unattractive, make the edging flush with the lawn.

Rising Grade

• On a roadside curb, the grass often naturally becomes above-grade over time. This is from the accumulation of thatch. While initially the soil was flush or 1 inch below the top of the curb, grass clippings and dead leaf blades can build up, causing the turf to elevate slightly over several years. Although not ideal, a lawn that is slightly above the road curb is safer and preferable to a curb that sticks up.

Regional Advice

• Contact your local government body, including your homeowners' association, to learn if any codes exist regulating soil grade abutting road curbs or garden bed edging, especially if it is exposed to a neighbor's or public-access property. Safety is the foremost concern, whether regarding pedestrians or lawn mower and maintenance equipment blades' clearances near curbs.