Placing Concrete

Filed Under: DIY Outdoor, Do it yourself, Home repair    by: ITC

Placing concrete is not difficult. Big jobs and little jobs all require the same basic steps:

• Preparing the surface and setting up the forms

• Figuring the amount of concrete you will need

• Pouring and finishing the concrete

The ground under the concrete must be compact and free from standing water and tree roots. Concrete on soft, unpacked ground will crack in a very short time. If drainage is a problem, put down gravel first and compact it.

Close in the area with 2 x 4’s. Drive in a stake about every three feet. The poured concrete is heavy and will press against the forms. So they must be supported to hold up the concrete. Make the forms level or at a slight incline for drainage.

Before you start mixing the concrete, decide how much you will need. A four-inch thick slab is standard, especially in areas where the ground freezes. One 94 lb. sack of premixed concrete will make 1 cubic foot. For a 4-inch slab, you will need 1 sack for every 9 square feet. Multiply the length by the width to see how many square feet are needed.

A 4-inch piece that is 3 feet x 5 feet (15 sq. ft.) would require two sacks. Be sure to mix a little more than you think you will need. You can always pour the extra into a mold to make a block or ornamental flower pot. A light coat of oil on the forms will prevent the cement from sticking.

Excess concrete can be poured into a mold to make blocks or flagstones or even into a can or milk carton to make a planter.

When the ground surface is ready, set up forms for the concrete. Nail stakes in place every three feet so the forms will hold up against the weight of the concrete. Place a board across the tops of the.

Pour the concrete in place. Avoid carrying it and handling it. Fill the form and level off the top by running a board across the top of the forms.

Slide a shingle or run an edger along the inside of the form boards to work out bubbles and work the gravel in. This will give a better appearance to the edges.

When the concrete begins to set up (20 or 30 minutes) and the water film on top has disappeared, trowel the surface smooth. Avoid excessive troweling. Place a groove every two or three feet because sooner or later the concrete will crack and the grooves let it crack into neat squares. Use an edger or jointer to give a professional look to the grooves and edges and to prevent corners from breaking off.

Cover the finished concrete with plastic or wet straw. The concrete will be ready to walk on in two or three days, but don’t drive over it for at least a week. Keep heavy vehicles, like trucks, off for at least ten days.

When the concrete begins to harden, smooth the surface with a wood float and finish with a steel trowel. Avoid excessive troweling because it weakens the concrete and may make the surface too smooth. Finally, brush for a textured, non-slip surface.

Level off the concrete with a straight board. This is called screeding. Don’t try to get the surface smooth, just level.

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