Concrete 101: How to finish concrete flatwork

You have your concrete form built, and you’ve placed the proper size of rebar in the bottom to strengthen the concrete. You’re ready to begin pouring concrete.

Before you get started with that step, however, you’ll want to make sure you have everything in place to properly finish your concrete. Concrete flatwork involves a few more steps than you might think, so it’s good to be prepared.

Here are the concrete finishing steps you’ll need to take after pouring your concrete:

Ensure the voids are filled. Gently tap the sides of the form with a hammer to vibrate the concrete mixture and help it settle into any remaining spaces. When you remove the form, you don’t want to see air pockets in the face of the concrete — especially if your project is something like building concrete stairs.

Screed the concrete. Grab a long (and straight) 2×4 and work with a partner to slide it across the surface of the concrete. Use a quick sawing motion to help ensure that the concrete settles into place. As you move the 2×4 across the surface, you can use a trowel to gather any excess concrete and use it to fill surface voids you’ve left behind. You’ll probably need to screed several times, until the entire surface is flat.

Float the concrete surface. The floating process uses a darby or bull float tool to smooth the surface of the concrete. This process brings water to the surface and helps to gently embed the aggregate.

Add your finish texture. If you are broom-finishing the concrete to provide extra traction, you’ll want to wait an hour or so, after the sheen has worn off. Pass a stiff-bristled broom in straight lines across the concrete to create a textured, anti-slip surface. If your project involves concrete stamping, now would be a good time to do that, too. Start with the area of your slab that was poured first.

Install joints. Unless you’re planning to sawcut the slab later on or have installed an expansion joint material, use a grooving tool to carve joints, or lines, into the surface of the concrete. This helps prevent cracks from appearing on the surface of the concrete in places you don’t want them. For depth, you’ll want these lines to be about a quarter of the way through the concrete — so about 1 inch deep for a 4-inch slab. For spacing, make these joints about 2–3 feet apart for every inch of slab thickness. A 4-inch-slab will need joints spaced at 8–12 feet.

Finish off the edges. Use an edging tool to shape a bullnosed edge around the perimeter of the slab. This helps prevent concrete from breaking off at the sharp edges, and it provides a finished look to the concrete.

Here at Custom Concrete Contracting, our Whatcom County concrete crews have been finishing concrete for years, producing concrete flatwork up and down Interstate 5, from Blaine to Burlington, and down Highway 20 to Anacortes. If you’d like to know more, please browse our website or give us a call at (360) 676-1665.