Measure the ground you will need for your wheelchair ramp. The Americans with Disabilities Act specifies that a gradient of 1:12 should be used in a ramp, meaning that for every inch of rise, a foot of vertical distance should be given. If your door is 6 inches off the ground, you need 6 feet of ramp to reach that height. Be sure to include space for the door to open, which may require a flat area at the top of the ramp.
Measure out the area needed, and clear it of bushes, shrubs or flowers. If you need to, flatten or level the ground. This will make the process of building the ramp much simpler, particularly if you will need to remove and reinstall the ramp at regular intervals.
Divide the total distance of the ramp by the number of pairs of posts you have. If you have three pairs of posts and your ramp is 6 feet, then your posts should be every 2 feet. Your posts should be at 2 feet, 4 feet and 6 feet from the start of the ramp. Placing a set of posts flush with the door will greatly secure the ramp.
Cut the posts to the desired height. The formula for working out the desired height is as follows: "Height of the post in inches = Distance from the start of the ramp in feet minus thickness of the planks of wood in inches." A post 4 feet from the start of the ramp, where the planks of wood are 2 inches thick, would therefore need to be 2 inches high.
Place the planks of wood across the pairs of posts once you have cut them to the desired height. Hammer them together with the nails. Be generous with the nails, as this will secure the frame of the ramp.
Lay planks at right angles to the post-connecting planks, so that they lie in the direction of travel. These will form the ramp itself. Nail these to the frame wherever possible to give greater stability.
Sand down the planks once they have been attached. Ensure that the surface is as smooth as possible to avoid damaging wheelchair tires. Varnish the surface and allow to dry. If you have sand or grit available, mix this with the varnish and paint on, which will increase traction. Insert handrails if necessary.