Measure the area where the ramp is to be located. An ADA ramp is required to be 36 inches wide and cannot exceed a 1:12 slope. For example, if you only need to go up 1 foot, then your ramp will be 12 feet long and 3 feet wide.
Mark the ramp area using stakes and string.
Measure how high you need to go to meet the entryway, and then calculate the length of the ramp using the 1:12 slope rule.
Cut the 2-by-4 or 2-by-6 wood and planks to create the form work that will hold the concrete in place. Dig deeper into the ground when placing the wood at the bottom of the ramp. The concrete needs something to stop it. You will also have something to screed the concrete with.
Place stakes around the form work to ensure it will hold the concrete.
Cut the top level of the form work to match the 1:12 slope. This way, you can use it as a guide when you screed the concrete level.
Place the rebar inside the form. Use 3/8-inch rebar spaced 6 inches apart to form a grid. Rebar will help to give the concrete the strength it needs and keep it from cracking too much.
It is best to overlap the rebar when making a longer ramp. Use wire to tie the rebar pieces together.
Mix the concrete according to the instructions. It should look like thick oatmeal.
Pour the concrete on the thickest part of the ramp first.
Pour evenly until the entire ramp is filled and concrete is all around the rebar.
Vibrate the concrete to ensure it gets in all the small spaces and eliminates any air bubbles.
With a wooden screed the width of the ramp, smooth the concrete so it is level with the form work. The wooden screed will help distribute the concrete to places where there wasn't enough poured and move the concrete out of places where there was too much concrete poured.
Smooth the concrete with a steel trowel.
After the concrete has been troweled and before it has hardened too much, apply a broom finish. Take a medium-bristle broom and lightly sweep lines onto the concrete. This will create texture, helping to ensure people will not slip when it gets wet.
After the concrete has hardened, remove the form work.
You will need to wait until the concrete cures completely before you can use the ramp. Then spray the concrete with water to help it from drying up too quickly.