Curbs and gutters are simple in design and complex in construction. A curb is a short concrete wall, usually about 6 inches high, that forms a barrier between a yard and a street. A gutter is a flat concrete slab abutting the curb which drains water away from the yard. Curbs and gutters usually are built as a unit and usually are the final elements in residential development before streets are paved. Forming curbs and gutters take a lot of wood and some precise skill.
Excavate the area for the curb and gutter with a shovel or mechanical excavator to 1 foot deep to allow a 5 or 6-inch gravel base and 6-inch layer of concrete. Tamp the dirt firmly with a hand tamper or mechanical compactor then lay down the gravel base and compact it solidly. The base must be the combined width of the curb and gutter, usually about 18 inches.
Build the forms with 2-by-12 boards for the back of the curb and 2-by-6 boards for the front of the curb and front edge of the gutter. Stand the boards on edge and secure them upright with wood stakes driven into the ground with a hammer behind them. Coat form boards with cooking oil or similar material to prevent concrete from adhering to them. Wipe on sealer using rags.
Complete the curb form by installing a 2-by-6 board at the height of the back curb form 6 inches above the top of the gutter. Put wood or metal spacers, coated with oil so they will not adhere to the concrete, every 6 feet to hold the front and back boards 6 inches apart. Fasten the two boards together to hold the spacers in place using metal clamps or 1-by-2 boards nailed across the tops of the curb form boards about every foot. Your are building a box with the bottom open and the top connected by the clamps or boards. Make sure all form boards are plumb and level.
Pour concrete into the forms from a wheelbarrow or concrete truck spout, tamping it firmly into all parts of the form with a board. Pour the gutter side with the concrete level with the top of the form. Pour the curb side to the top of the curb forms. After the concrete has set, remove the front curb board and smooth the curb and gutter surfaces with a trowel and special concrete finishing tools which shape the curb edges. Create expansion joints in the gutter with a finishing tool that makes indentations wherever spacers were placed in the curb form. Remove the spacers and fill those joints with concrete mortar. Remove the front gutter and back curb boards after the concrete has fully set.