Many concrete patios and sidewalks are less than 2 inches thick and lack metal reinforcing. In areas subject to freezing winters, such slabs usually crack. A long-lasting pad prevents the problem.
A solid concrete pad is 4 inches thick, rests on a bed of well-tamped gravel, and is reinforced with reinforcing wire mesh. A concrete slab may be raised one step above the yard or an adjacent patio surface, or it can be set just above ground level. If the pad is 75 square feet or smaller, you don't need to worry about drainage.
Though it may feel solid a few hours after pouring, concrete takes a week or two to achieve full strength. Wait at least three days before exerting heaving pressure on the pad.
You'll need roughly a day to excavate, build forms, mix concrete, pour, and finish the pad's surface. Before you begin, determine the location for the pad and remove any sod. Make sure you're able to check for level and square, mix concrete, and smooth out a concrete surface.
Excavate topsoil and tamp down about 2 inches of gravel. Cut 2x boards to use as forms for the pad. Fasten them together to form a rectangle. Use a framing square to check the corners for square. Fasten the boards to stakes driven into the ground, and check for level and square.
Backfill with soil behind the form boards so too much wet concrete can't ooze out from the bottom. Cut wire reinforcing mesh to fit, then lay it on top of stones so it's near the center of the pad's thickness when you pour the concrete.
Mix the concrete and pour it into the forms. Using a board long enough to reach from form to form, screed the surface: Drag the board, using a side-to-side motion as you move it across the length of the pad. Repeat until the surface is level and has no low spots.
Using a wooden, steel, or magnesium float, smooth out the entire area. With the float held nearly flat, lightly scrape across the pad in long, sweeping arcs. As you work, water will rise to the top. Keep smoothing as long as the surface is wet. Once it has started to dry, lightly drag a broom across it to create a nonslip surface.
Slip the point of a mason's trowel between the form and the concrete and slice all around the pad to a depth of 1 to 2 inches.
Run an edger around the perimeter to round off the corners. This will prevent chipping. Press lightly and repeat until the corners are smooth. Let the concrete set for a day, then pry away the forms.
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