Building a ramp over existing steps is a straightforward project you can complete during a weekend to allow wheelchair access into a house. You'll need plywood sheets and sturdy wooden posts to construct a strong, reliable ramp. Anchor the ramp over the stairs using 4-inch screws.
Extend the measuring tape from the top of the doorsill to the ground beyond the lowermost step to help determine the angle or rise of the ramp. According to the Americans with Disabilities Act, for every 1 foot of rise, you need 12 feet of run or length. Multiply the height of stairs by 12 to arrive at the length of the ramp.
Cut three sheets of 3/4-inch plywood to the desired length of the ramp using a circular saw. Also cut three pieces of 3/4-inch-thick plywood to 5 feet lengths to serve as a landing at the top of the stairs.
Measure and cut four wood posts to the determined length of the ramp, plus 1 foot, using a handsaw. The posts support the landing of the ramp. Also cut two posts for every 2 feet of ramp length to support the ramp itself.
Use a protractor to form an 8-degree angle at the top of the pairs of posts that support the ramp. Cut the posts along the marked line using a circular saw. Do not form the angles on the landing support posts.
Glue the three plywood sheets identical to the ramp length together, on top of each other, using wood glue. Ensure the ends of the identical sheets match each other before securing with adhesive. Drive 2-inch nails along the edges of the plywood sheets to secure them together, spaced 6 to 8 inches apart.
Join the three 5-foot-long plywood sheets together, on top of each other, using wood glue. Also drive nails through the edges to secure the sheets together, creating a landing for the top of the stairs.
Dig two holes in the ground next to your home, on either side of the top of the stairs, using a post hole digger. Ensure the holes measure 12 inches deep, and space these 38 inches apart. Measure 5 feet away from the previous parallel holes and dig another pair of holes in the ground, spaced 38 inches from each other. These four holes will hold the posts for the landing.
Dig a third pair of holes in the ground, 2 inches apart from the last pair. Space the holes 38 inches from each other. Continue to dig additional pairs of holes every 48 inches along the span of the ramp to support the posts.
Prepare concrete according to label directions. Lower the first four posts in the holes, in turn, and slowly pour concrete around them. Repeat the process to set the remaining posts in the holes, with their angled ends facing upward. Ensure the top of the angle is closest to the house and the lower end faces the end of the ramp. Allow the concrete to cure.
Center and lower the plywood landing on the four posts. Drive 4-inch wood nails to secure the plywood to the posts.
Lower the plywood for the ramp over the angled posts, and secure with 4-inch nails.