Sep 24 , 2019
A darby flattens the wet concrete.
Close up: Edging tool
An edging tool gives the concrete a round edge.
A groover makes joints in the concrete to control cracking.
Close-up: Magnesium concrete hand float
A float compacts the concrete surface, giving it a smooth look. Putting a smooth, durable finish on concrete is a skill you can only master with the proper set of tools and practice. We’ll show you the tools and how to use them for each step of the concrete finishing process. And equally important, we’ll help you determine when the concrete is ready for the next finishing step.
But you really can’t practice these techniques except on real concrete. So it’s smart to start with a small project like this garbage can pad. When you get the hang of it, you can move up to a larger slab. But keep in mind that finishing larger slabs (more than about 100 sq. ft.) is trickier because the concrete may set up too fast.
In this article, we’ll show you how to level the concrete in the forms, round over the edges and make a progressively smoother finish. But we won’t show how to build forms or fill them with concrete.
Each step in the process requires a different tool. You can make the screed (Photo 1) and darby (Photo 2) from scraps of wood. The rest you’ll have to rent or buy. You’ll need a magnesium float ($15 to $25), an edger ($5 to $20), a grooving tool ($10 to $30) and a steel trowel ($8 to $40). Pros buy expensive top-quality tools that will stand up to the rigors of daily use, but less expensive versions are available at home centers and hardware stores and will work fine for occasional home use.
Concrete is a blend of Portland cement, sand, aggregate (gravel) and water that harden when mixed. While there are additives that can slow down or speed up the process, and special bagged mixes that set fast, in general, the speed of the process largely depends on the temperature and humidity.
Hot, dry weather accelerates the hardening process, sometimes so much that it’s nearly impossible to complete all the finishing steps in time. Work while your project is in shade if possible. On cool days, you may spend a lot of time waiting for the concrete to reach the next stage. That’s why we can’t give you exact waiting times. But we’ll show you how to tell when the concrete is ready for each finishing step.
Video: How to Pour a Concrete Slab
Screed and darby the concrete right away
Screed the concrete
Push or pull the screed board across the forms with a back-and-forth sawing motion. Shove concrete into low spots in front of the screed board. Repeat to remove excess concrete.