There is not a lot of black magic in building simple concrete forms for a walkway, flowerbed, patio, or driveway - only a lot of hard work.
General materials include:
-2 x 4s or 2 x 6s
(The quantity is simply the straight length of the project, times two).
To begin, pull a straight-line (string) from one foot past the starting point to one foot past the ending point. Measure the width and pull a parallel line the same distance. You are now ready for the manual labor: excavation. Remove enough soil to allow for leveling, plus a sand or gravel base of at least two inches. If all the concrete is to be above ground, this is the only excavation required. Ground level concrete will require additional soil removal for desired thickness.
Keep in mind that the process of pouring concrete creates a tremendous amount of pressure, especially with ready-mix. To prevent "blowout," the support structure must be of sufficient strength to withstand such pressure. Blowout is the term professionals use in describing an event in which the forms are not strong enough to contain the just-poured concrete. When in doubt add more stakes.
For most home projects 2 x 4s or 2 x 6s work very well for straight runs. Stakes most commonly used are wood 1 x 2s that are 18 to 24 inches in length. We prefer 2 x 2s, as they are much easier to pull once the project is complete. Note: to cut cost, rip a 2 x 4, cut to length and "V" one end of each stake.
When using 2 x 4s, place them on edge -- end to end -- on top of the base. The 2 x 6s will be outside the base instead of on top. Drive in stakes at intervals of no less than 2 feet. Place two stakes at each butt joint. Drive two duplex nails in each. Cover and pack dirt against the outside of all exposed forms.
Up to this point, we have only talked about straight-line forms. For curved forms cut 3/8 inch plywood the proper width, either 4 or 6 inches. (Actual cuts to match 2x4 & 2x6 would be 3 ½ or 5 ½, respectively.) When using plywood, extra stakes will be required.
A shop tip: use 4-inch steel landscaping edging for curves, either 4-foot or 10-foot sections. You can reuse the edging after project completion.
You can now lay the rebar. The quantity will depend on the weight or pressure exerted on your finished project.
A driveway should have a criss-crossing pattern of 15 to 18 inches whereas a sidewalk will probably only require a pattern of 24-inch interval grids. A single stick of rebar will sufficiently support edging around a flowerbed.
Begin with a single stick of rebar placed two inches inside and parallel with the form. Seat the rebar in chairs at 3-foot intervals. The chairs will lift the rebar the correct height off the base. Continue laying the rebar parallel to the forms at suggested intervals making sure the two outer bars are two inches from the form. Cut the rebar for cross members and tie with wire at desired intervals to form a grid pattern. These cross bars extend only to the two outer parallel bars.
Once you have your
forms in place, you will be ready to order and pour concrete.
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