Concrete is a strong and versatile building material. With the advent of ready mix cement, handy homeowners can do a lot of their own concrete construction. When it comes to pouring concrete, everything starts with the forms. Ensuring your concrete forms are both accurate and strong will go a long way toward a finished project that will stand the test of time. For ease of use and versatility, it's hard to beat wood as the concrete framing material of choice.
Determine the design of your concrete project. Lay your outline on the ground.Use the tape measure to ensure correct measurement and the carpenter's protractor to verify correct angles. Drive stakes into the ground at each corner of the outline. Tie twine to the first stake and string it around the perimeter of the outline, tying it to each stake. Use the level to ensure a straight, level line.
Place the first piece of wood sheathing along the string line. The width and depth of the sheathing is dependent on the amount of concrete being poured. 1-inch by 4-inch boards are generally stout enough for up to 4 inches of concrete. Thicker slabs require thicker sheathing, which may be pine boards or plywood.
Drive sharpened stakes on the outside of the sheathing at regular intervals. A 4-inch pour normally requires a stake every 32 inches, depending on how firm the underlying soil is. Decrease the spacing for deeper pours and for loose soil. Nail the sheath to the stakes as close to the string line as possible.
Adjust the sheathing in or out by packing soil around the stakes. Use the builder's level to ensure the sheathing is plumb. Ensure that the string line remains above the concrete forms to provide a guide for a straight line.
Repeat these steps for each side of the perimeter. Ensure that the corners are properly joined to prevent leakage. Concrete should set for three to four days before removing the forms.
Straight, flat lumber without knotholes provides the best concrete forms. Thick concrete pours of greater than 8 inches may require a second round of stakes set a couple of feet behind the concrete form with kickers nailed to the bottom of the rear stakes and the top of the form stakes to provide additional stability.