Pouring a concrete driveway involves basically the same procedures as pouring a patio. However, because of the extra weight requirements, driveway construction is often well-regulated by local building codes. Make sure you understand all code restrictions before you begin construction. You also must have proper permits. For instance, most municipalities have strict rules governing the steepness, thickness and width of the driveway, as well as the means by which it joins the curbing.
Design Considerations
Most single concrete driveways today are made of a single slab instead of the double-slab ramp drive that has paving only in the areas of the wheels and grass in between. A single slab provides a wider usable surface to serve the wheelbase dimensions of more car models. The trend of the times has reinforced the single slab, perhaps partly because a single slab requires less edge forming. Then, you do not have to mow the grass between the strips. However, the double slab (also called “double strip”) is a functional, economical driveway well suited to the do-it-yourselfer. In fact, many people prefer the grassy strip as a landscape feature. Two-car driveways, on the other hand, must be of full-slab design.
Design Specifications
To Unite The Garage And The Street.
The edge of the driveway should fall about 1 inch below the garage floor, to prevent water from running into the garage. The drive should slope downward from the garage to the street. If your garage sits downhill from the street, install a drain where the driveway meets the garage. Where the driveway meets the street, raise the edge of the drive just a little above the road to prevent water and debris from flowing from the street into the drive.
Size Of The Drive.
In most instances, the driveway is cast so it is 2 inches above ground level. Slabs for passenger cars are 4 or 5 inches thick; however, a slab that will have truck traffic should be 5 or 6 inches thick. Some concrete contractors make the area near the street 8 inches thick to accommodate the extra weight of trucks that might pull partly up onto the concrete drive-way for delivery or collection. A slab for a single-car garage should be between 8 and 10 feet wide, and one for a double-car garage should be between 15 and 20 feet wide-widths up to 22 feet are common.
Pitching The Concrete Driveway.
The driveway should also provide a pitch of from 4 to 2 inch to the foot; this is considered a minimum in most areas. You can give a sideways pitch to the entire drive, but the best plan is to crown the driveway, providing pitch from the center to both sides. To create the proper pitch from the center to the edges, the slab is poured in two stages. First, the form for the entire drive is built. Then a centered stopboard is inserted lengthwise in the form. It runs from the garage to the street, and must be high enough to create the correct pitch. If your driveway is to be 20 feet wide, the center of the pour must be 5 inches (10×2 inch) higher than the outside edges of the slab. The form boards at the garage and street must correspond to this pitch, and the top edge of the centered stopboard must be 5 inches higher than the side form boards. The center joint between the two sections of the slab will be held together with a butted construction joint.
Building Driveway Forms
Entryways.
For better appearance and easier access, use curved forms to provide curved entryways on both sides where the driveway meets the street. This design is sometimes utilized at the garage Entryway.
Base Preparation
Once the area is well excavated and smoothed, tamp it solidly. Unless the soil is extremely hard packed and well drained, lay the base as discussed earlier. Most codes will require 4 inches of gravel or crushed stone plus 2 inches of sand. Tamp the base materials. Lay reinforcing mesh on rocks, placing it so that it doesn’t touch any of the forms. Install isolation joints between the garage and the driveway and between the drive and any existing sidewalks. Asphalt impregnated cane fiber is the most commonly used material.
Making the Pour
The Initial Pour.
When pouring a slab as big as a driveway, start at the garage and work out on the street. If you lay the length of the driveway in sections, install a stopboard at about 10 feet; it will then correspond to the placement of control joints. Place the concrete in this first section only. Tamp and spade as needed, giving special care to edges and tie bars. Screed the concrete off and place it into the adjacent, unpoured section. If you don’t screed off, some places will have a lot of extra concrete, which must be moved; other spots won’t have enough. You would have to solve these problems by moving the concrete, causing possible separation and weakening of the pour. Let the slab set up. Cut any control joints as needed, and give the driveway a lightly broomed finish.
The final pour
Once the first half of the slab is finished, remove the stop-board. This will not be easy; it is hard to slip the tie bars back through the holes in the stopboard. Repeat the entire process for the remainder of the driveway, in 10-foot sections as needed to complete the driveway.