Calculate the length of your ramp. The Americans With Disabilities Act mandates that wheelchair ramps can not slope down more than 1 inch for every 12 inches of length. Measure how high the surface is that the ramp is leading to, then multiply the number of inches by 12. This tells you the minimum length that your wheelchair ramp will need to be. It is acceptable to construct your ramp longer than this length, but not shorter.
Decide what design will work best on your property. The most common layouts for wheelchair ramps are the L Shape, U Shape and Switchback. These designs allow the wheelchair ramp to travel the required distance without stretching endlessly across the property. Remember that both the top and bottom of the ramp should be level with the surface they connect to. The bottom should also lead directly into a sidewalk or driveway so that there is easy access to the ramp.
Check with your municipal government to find out if you are required to obtain a building permit for your wheelchair ramp. Some cities will require a permit while others will not. The department that issues permits will vary from one location to the next. Contact the office of the City Clerk in your town to find out who is responsible for building permits and code enforcement, and then check with that office to get approval to construct your wheelchair ramp.
Use snap chalk to mark the area where your wheelchair ramp will be constructed. This chalk is on a string that pulls out like a tape measure. Hold the chalk against the ground and give it a quick snap to instantly have a chalk line marking the area. You should not only mark the length and layout of where the wheelchair ramp will be, but also the width of the ramp. The wheelchair ramp needs to be a minimum of 36 inches wide, although 40-45 inches is ideal and will provide more room to maneuver.
Dig your post-holes. Mark an area on your chalk line where your posts will be located. There should be a post located at each end of the wheelchair ramp, and spaced every 48 inches in between. The space between can be adjusted a little to compensate for your design, but having a post every 48 inches will provide solid support for the weight of your ramp. Each post should be accompanies by an adjacent post directly across, on the other side of the ramp. Once all locations have been marked, use a set of post hole diggers to dig a hole 24 inches deep at each post location.
Plant your posts in the ground. Start by cutting your posts to length. Each posts should be long enough to extend from 24 inches below ground to 36 inches above the floor of the wheelchair ramp. This means that the posts at the high end of the ramp will be longer than the posts at the low end, so measure and cut accordingly. You should use 4x4 boards for the posts, and secure them with concrete. This step is easier if a friend can assist you, so that one can hold the post steady while the other pours the concrete. Check the post with a level to make sure it is perfectly vertical before the concrete has time to dry.
Measure your posts and mark the location of the sideboards. Start at the high end of the ramp and identify the spot that is level with the area the ramp leads to. Mark a spot on the post that is 2.75 inches below this, to account for the space that flooring will use. Mark this area on both the inside and outside of each posts at the high end of the ramp. Continue down to the next post, dropping your mark slightly to accommodate for distance. You are creating a slope that descends 1 inch for every 12 inches of distance, so if your posts are 48 inches apart, the mark on the next post will fall four inches below the mark of the previous post. Repeat this process until you reach the end of the ramp.
Attach your sideboards to the posts. Use 2x4" studs to create your sideboards. You will be placing one sideboard on each side of the post (inside and outside). Each side should be at the same level/height on the post, as well as the same level as the post directly adjacent on the other side of the ramp. Start at the high end of the ramp. Hold the sideboard in place and hammer a single nail through the board into the post. Using a single now allows you the freedom of moving the board to adjust its position on the next post. Put 2-3 nails in the board at the second post, then return to add additional nails at the first one. Repeat this process until sideboards run all the way down the inside and outside edges of the wheelchair ramp.
Construct the floor joists for the wheelchair ramp. Again, use 2x4" studs for this part of the ramp. The length will depend on how wide you chose to make your ramp. They should be long enough to go from the outside edge of one side of the ramp, to the outside edge of the other side. Lay these boards flat across the tops of the sideboards you created in Step 8 and nail them into position. They should be spaced so that you have one joist every 24 to 36 inches down the length of the ramp. There should also be one at each end of the ramp at the very edge.
Build the floor of your wheelchair ramp. Stand ¾ inch thick plywood makes the best floor for the ramp. Use a circular saw to cut the plywood into pieces that will read across the ramp from side to side. You may also need to cut notches in some pieces so that they will fit around your posts. As the plywood is cut, lay the pieces on top of the joists your built in the previous step. Use a hammer to nail the plywood into the joists with short nails. Place several nails into each joist to hold the plywood tight. This will prevent the wood from warping or creaking.
Create side rails for the wheelchair ramp. Each post should extend roughly 36 inches above the floor of the ramp. Take advantage of this space by nailing 1x4" boards to the posts along the entire length of the ramp. This creates a sturdy side rail that will help prevent accidents and also give people something to hold onto if they should need assistance making it all the way up the ramp.