Broom-Finished Concrete Flat Work

Good concrete starts with a sturdy base. Once I’ve removed the topsoil and confirmed the remaining soil is free-draining and well compacted, I mark the location of the walk on the house and use these marks to place 18-in. stakes that receive the 2x4 formboards. At the opposite end of the walk, I spread the forms to the correct width and attach a formboard for the end of the walk. Then I pull diagonal measurements to square the corners and use a level to slope the walk away from the house 1⁄4 in. per ft. Once everything is square, I drive the rest of the form stakes and attach the formboards with 2-in. screws.

As I’m pouring the walk, I lift the reinforcing mesh and rebar into the middle of the concrete and screed the concrete flush with the top of the forms. Then I use a bull float to smooth the surface and to force the aggregate down into the concrete. Bull-floating brings up bleed water that must evaporate before finishing can continue. When the bleed water is gone and a footprint leaves a 1⁄4-in. impression in the surface, it’s time to start finishing with a mag float. The mag float brings up a layer of water and cement particles known as cream. Once there’s a nice layer of cream, the edges can be rounded with an edge tool, and the control joints can be made with a groover.

After a pass or two with a steel finishing trowel, the walk can be finished with a stiffbristle broom pulled across its width. Rinse off the bristles with every pass for distinct ridges that provide maximum traction.

Step By Step

Square the forms. With a formboard on the end of the side forms (opposite the house) establishing the width of the walk, shift the formwork left or right until measurements from opposite corners are equal, which means the forms are square. Drive in stakes on both sides to keep the forms from shifting, but don’t attach the screws just yet.

Straighten the sides. Use a taut string to straighten the sides of the formwork. Drive in stakes every 2 ft., and screw through them into the sides of the form. Backfill against the forms with soil or gravel to prevent bulging.

Add steel for strength. Three rows of 3⁄8-in. rebar and a grid of 4-in. reinforcing mesh add strength and help to control shrinkage. Rebar dowels inserted into the foundation prevent the walk from sinking near the house. Make the holes with a rotary hammer

Fill and screed. Fill the forms so that the wet concrete is just over the tops of the forms, then screed off the excess, using the forms as a guide. A helper or two moving concrete ahead of the screed makes this process easier.

Break out the bull float. Level the surface, and force the aggregate into the mix with a bull float. Keep the leading edge raised as you push or pull to avoid digging into the surface. Two or three passes is enough.

Make cream with a mag float. After the bleed water has evaporated, use a magnesium float to bring up the layer of water and cement particles called cream. Then round the corners with the edging tool, and make control joints every 5 ft. with a 2x4 and a groover.

Use a steel trowel for a smooth finish. With the grooves cut and the corners rounded, use overlapping arcs with a steel finish trowel to tighten up the surface before brooming.

Broom finish for traction. Special concrete brooms exist, but a regular push broom with stiff bristles works fine, too. Keep the texture perpendicular to the traffic direction. Once you’ve finished brooming, go over the corners and control joints again.

A kit for concrete

Concrete work requires some special gear, but you can outfit yourself with all the goodquality tools you need for less than $300. The biggest-ticket item is a bull float ($175), but you can rent one for about $16 a day.

A better bull float. Marshalltown’s bull float with RotaLeveler makes it easy to keep the float’s leading edge raised when both pulling and pushing. Conventional bull floats have a fixed connection that’s harder to control, especially on large slabs