Concrete offers a strong base on which to park your vehicles. If your drive is too narrow or too short to handle all of your parking needs, you can extend it with additional concrete. Unless the extension is very small -- less than 30 cm (1 foot) wide -- hire a professional to pour it.
Dig the soil to a depth of at least 12.5 cm (5 inches) where you want to pour the extension. This includes the area right next to the current drive. Clear away all the soil and debris from the side of the concrete.
Build your concrete forms with 5 cm by 10 cm (2 inch by 4 inch) dimensional timber to the desired length and width of the extension. Drive stakes on the outside of the forms to brace the boards and nail the forms to the stakes.
Level the top board of your forms with a transit or a long carpenter’s level. Account for the current slope of your drive. A standard drive will slope a minimum of 6 mm (1/4 inch) for every 1.2 lineal metres (4 lineal feet). After determining the slope of the existing driveway, adjust the top level of your forms to match the grade.
Fill the bottom of your forms with sand 2.5 or 5 cm (1 or 2 inches) deep. The sand stabilises the concrete and will reduce future cracks.
Drill holes 15 cm (6 inches) deep on the exposed edge of your existing drive and insert rebar rods into the holes. The holes should be halfway between the surface of the drive and the base of the concrete. Space the holes 40 cm (16 inches) apart.
Use a hammer to drive the rebar rods into the holes. The rods should be long enough to come within 2.5 cm (1 inch) of the opposite edge of the forms. For instance, if you’re adding a 60 cm (2 foot) strip to the side of your drive, cut the rebar rods 72.5 cm (29 inches) long. This allows you to drive the rods 15 cm (6 inches) into the drilled holes, leaving 57.5 cm (23 inches) of rod extending to the other end of the forms.
Add additional rebar to the inside of your forms to comply with building regulations. This rebar will run at a right angle to the rods inserted in to the existing drive and you will connect them at the intersections with rebar ties.
Pour and shovel the concrete evenly, using a concrete screed, or a board, to level off the top. Use a hand trowel to work the concrete by rubbing back and forth until the surface is level.
Allow the concrete to cure undisturbed until hard, up to 48 hours, before stripping away the concrete forms and filling around the new drive with soil.
If you’re not experienced in pouring concrete, hire a contractor to pour the extension. Wear protective eyewear and long-sleeve shirts, long trousers and gloves to keep wet concrete off your skin.