How do I Build a Concrete Sidewalk?

Lou Paun

Making a poured concrete sidewalk is a relatively straightforward task, well within the capabilities of most do-it-yourselfers. It’s heavy work, though, and some tasks are time-sensitive. Strong helpers make the job manageable.

A cracked concrete sidewalk.
A cracked concrete sidewalk.

Proper preparation of the site is essential for a level, long-lasting concrete sidewalk. Pouring concrete onto unprepared ground will result in a sidewalk that is uneven and is likely to crack and break. The more freeze-thaw cycles the location has each year, the likelier it is that the concrete sidewalk will break. Proper site preparation is especially important in locations with cold winters.

Wet concrete being poured.
Wet concrete being poured.

First, dig out the area that will be filled with concrete to a depth of at least 6 inches (15.2 cm). Make the bottom as flat as possible. Fill the area with about 4 inches (10.2 cm) of crushed gravel. Tamp the gravel down until it is hard.

Then build forms around the edge of the area, using 2 x 4s set on edge and held in place by stakes. The top edge of the boards should be the height you want the finished concrete sidewalk to be -- usually even with the ground or slightly above the ground. They should be completely level.

The entire pour site should be prepared before the concrete truck arrives, because pouring concrete is fast work. Ask the truck driver to pour as evenly as possible along the entire length of the concrete sidewalk, and rake the concrete into place as rapidly as possible. Then level the concrete by moving an extra board, called a screed, along the surface. The screed should extend across the sidewalk, resting on the form boards on both sides. Jiggle it back and forth over the concrete while pulling it from one end of the sidewalk to the other, to smooth out any uneven spots.

Let the concrete sit for a little while, until some water rises to the surface and begins to evaporate. The weather conditions will dictate the length of time needed for this, but it usually takes about an hour. The concrete mix should be firm but still pliable. Then smooth the surface with a trowel. If you want beveled edges on the concrete, press the edges in. Score a line about 1/2 inch (1.3 cm) deep in the concrete about every three or four feet (0.9 - 1.2 m) along the concrete sidewalk. This will make it easier for the concrete to contract and expand during freeze-thaw cycles and reduce cracking.

Cure the concrete by keeping it wet for about three days. If weather conditions are favorable, this can be accomplished by misting the new concrete sidewalk several times a day. If the weather is dry or windy, lay wet burlap over the sidewalk to keep it evenly moist. If frost is expected, add a layer of straw to insulate the concrete sidewalk while it cures. After four days you can remove the forms and walk on the new concrete sidewalk, but the concrete will continue to cure for about a month.

Power trowels might be used to impart a smooth surface finish on freshly poured concrete slabs.
Power trowels might be used to impart a smooth surface finish on freshly poured concrete slabs.

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