
Whether it’s a wall, slab, or some type of concrete pavement, it typically will need an edge. Catching an edge requires training and skill. The first step is understanding that not all edges are the same. An edge for a floor is a different process than compared to an edge for a driveway, sidewalk or curb. The difference lies in the technique – the quality of the edge is dependent on how many times you go over the edge.
Like anything with concrete work, it starts with timing. Find that “goldilocks” point of time between it setting up enough to work and too hard. You want some stiffness with a little bit of integrity. But too set will slow progress.
“The first step is to clean the top of the form before you start catching the edge” advises Nick Demonte, ITF cement mason coordinator from the Operative Plasterers' & Cement Masons' International Association (OPCMIA). This is typically done with a margin trowel: hold the trowel along the edge and open it up, then start using your edger. This training is one of the basic lessons the OPCMIA teaches apprentices. You mention cleaning top of edge but he talks about running the margin trowel on the inside of the form. This should be the second step.
The different radius of edges is determined by the radius of your edger. For the new talent on your team, Demonte suggests starting beginners with the wider 6-in. edger. “For beginners, we want them to use the wider edger to learn what the flatness of an edge is,” he says. Similar to training people on using a float, it all about how to control the tool along with the stiffness of the concrete.
Another factor to consider is the weight of the tool itself. It’s possible to edge if the concrete is super wet. Doing so, however, requires experience and greater technique to hold the tool up and stopping it from sinking in; some stiffness in the concrete will help keep the tool stay flat. Holding the angle of the tool too high will take cream (or paste?) away, think more around 5-10 degrees, enough so that the front of the tool doesn’t “dig” back into the concrete. Probably just refence either cream or paste.
Consider also your body position. It’s common to work on your knees but Demonte prefers to work from his feet. He recommends to stand. “You can cover more ground by standing up,” he says. “You hold your stance a little wider. The wider your stance will help preserve your back.” Always work in one pass - an arm’s length from one side to the other.
Practicing this technique will be key as your technique shouldn’t change. A good, solid, practiced technique will be how you gain speed and work the concrete faster.
“There’s different techniques for different types of edging,” says Demonte. A finished floor is a different story. For catching a regular edge, widening your stance should make it easier to bend over and work the trowel at an arm’s length along the inside of where the form and concrete meet.
A line should indent on the outside part of the edge of the concrete (away from you) as the edger coasts over the concrete. This indentation tells you whether you dug in or just touching the surface. Follow using your float to take away the line without closing the edge. This will also help you stay flat. Reposition and continue using the same technique until the slab has been completely edged.
Work with purpose. Work with caution. “One of the biggest misconceptions that people make is when there’s a big aggregate – a piece of rock on the edge – and go and take that rock away,” notes Demonte. “Now you have to fill that hole. The biggest mistake people make is they push down on the edger to fill that hole. Now, what they’ve done is haven’t made a flat edge, they’ve made an indentation (low area?) by the form.”
Again, concrete is all about timing. Having the knowledge on when to start the edging process comes with experience. Typically, the rule of thumb is that the indentation of the knee board should not exceed 1/8 to 1/4 of an inch.
Lastly, remember to clean your tools and properly store them away.