CURBS: VARYING CONSTRUCTION MATERIALS & WORKFLOWS TO MAKE THE PERFECT CURB

3D ModelTechnology

Aug 8

Curbing varies in both method and materials depending on the geographical location. The climate that it needs to withstand and the functionality that it needs to serve have to be considered. Curbs are necessary for providing barriers, structural support, protecting landscapes, and directing water flow towards drains. Installing a curb is a laborious process, often including skilled laborers working on their hands and knees using guides or boards to ensure the lines are straight and that the reveal is correct. Machines have become available over the years to make the manual process more manageable, and depending on your budget, there are some different options available on the market. Regardless of which technique is being used to build curbs, it's essential to pay attention to the curb's line, grade, and overall quality.

Curb Materials

Common curb types are made of asphalt (aka bituminous concrete), cement, or granite. Asphalt curbs do not have a base foundation to support them, are less durable than concrete or granite, and are less expensive. Bituminous concrete is made up of asphalt cement and well-graded aggregate. It is then compacted when hot and formed into a dense mass. This type of material is considered to be more flexible than concrete. Concrete curbs are the primary form of curb in the west. They can be constructed in many different shapes depending on the region that it's for. Granite is the most durable type of curb and is often used in parking lots and roadways.

Curb Machines

From small curb rollers that fit in the back of a truck to slipform pavers that don't, there are machines available to alleviate some of the pain associated with this labor-intensive process. For example, a slipform paver is a large machine that acts as an extruder to create the curb shape while also finishing the project. It comes with a built-in hopper and belt system. The less expensive slipform pavers are still guided by the string system, where you must set up a string line used to guide the curb machine. However, some more advanced ones come equipped with 3D guidance and smart sensors that remove the machine's need to be string-guided; depending on how much curb work you do and what your budget looks like, it may be worth the investment to purchase one of these.

Workflow Differences

When creating curbs, it is crucial to consider which region you're in because the process can vary from one state to another. For example, here in Massachusetts, curbs are constructed after the asphalt binder, whereas in our neighboring state, Connecticut, the curb is put in before the asphalt binder. The reason is that Connecticut uses catch basins with a concrete top that has a curb line in it already, so they must build the curb before the binder. It is common for what is known as cape cod curbs to be put on top of the asphalt in roads, locking it into place.

When it comes time to grade your curblines, there are three significant factors to consider. First, how far behind the curb do you have to grade? If you are using a curb machine, you will need additional space behind the curb. To accomplish this, you may need to disable overcut protection on your machine to allow it to grade past the curb. Second, is your curb bottom sloped at the same slope as the road, or is it steeper? This applies to concrete curbs where your road cross slope may be at 2%, but the bottom of the curb may be at 3-4%; if you don't account for this, you may grade your basecourse far too high at the back of the curb. To grade for this, you may have to change where your guidance is based on the blade. Lastly, if you have a parking lot with many islands or peninsulas, you may struggle to navigate your blade or dozer around these obstacles while grading. To make your life easier, you might request a finish grade model without the islands or peninsulas so that you can grade clear through the curblines allowing for a much easier and faster grading job.

ECI's engineers have hands-on experience with paving and curbing and, of course, with modeling. If you need assistance with your next curbing project, give us a call.