How to Build a Handicap Ramp Over Existing Steps

Measure from the top of the doorsill into your home to the base of the stairs on the ground. To comply with the Americans with Disabilities Act safety standards, the ramp’s rise -- the angle of the ramp -- must not exceed a 12 to 1 ratio. In other words, for every 12 inches of length, the ramp should only rise 1 inch. To determine the length of the ramp, multiply the stairs' height by 12. For example, if the stairs are 12 inches tall, the length of the ramp would be 144 inches.

Cut three pieces of 38-by-3/4-inch plywood with a circular saw to match the length you determined in step 1. Cut three pieces of 60-by-38-by-3/4-inch plywood to create a landing at the top of the stairs. Also, cut 6-by-6-inch posts to support the ramp. Cut six posts to match the height determined in step 1, plus 12 inches to create supports for the top landing of the ramp. Cut an additional two posts for every 48 inches in ramp length, to support the ramp itself. The height of the additional posts is determined by the length of the ramp. For example, if the ramp's length determined in step 1 is 124 inches, you need four additional posts. If the ramp is 36 inches long, you need no additional posts.

Cut the pairs of posts to support the ramp at an 8-degree angle. Use a protractor to determine the angle on the ends of the posts and cut them with a circular saw. Do not cut the first four posts for supporting the landing.

Apply wood glue to the top of one of the plywood pieces that matches the length of the ramp. Place the glue a half-inch in from the outer edge. Place a second piece of matching plywood on top. Apply wood glue to the second plywood piece around the edge, as you did the first piece. Place the third matching piece on top. Hammer 2-inch nails around the outer edge of the plywood sheets. Drive the nails a half-inch in from the outer edge of the stack so the nails secure the three sheets of plywood together. Space the nails every 6 inches to create the ramp.

Repeat step 3 with the three 60-by-38-by-3/4-inch plywood pieces. Use wood glue a half-inch in from the edge between the three pieces. Secure them with more 2-inch nails spaced every 6 inches to create the top landing for the ramp.

Dig two 8-by-8-inch holes on either side of the top of the steps, next to your home. Make the holes 12 inches deep and spaced 38 inches apart. Use a post hole digger to dig the holes. Dig two more holes 60 inches from the first, also spaced 38 inches apart. The four holes in a square formation will hold the posts to support the top landing.

Dig two additional 8-by-8-by-12-inch holes 2 inches from the second set of holes from step 5. To create the holes to hold the post for the top of the ramp, space the holes 38 inches apart. Dig additional pairs of holes every 48 inches down the length of the ramp as needed. The number of posts cut in step 2 determines the number of additional holes.

Prepare a batch of quickset concrete according to package directions. Insert the first four posts into the first four holes you dug for the landing supports. Center the posts in the holes and fill them with concrete until level with the ground. With the angled ends up, insert the ramp support posts into the holes. Center the posts and line the angled ends so the top of the angle is closest to the house and the lowest points toward the end of the ramp. Fill the holes with quickset concrete. Let the concrete set according to the package’s instructions.

Place the landing plywood pieces on top of the first four. Place the plywood flush against the edges of the posts. Use a nail gun set with 4-inch nails to secure the plywood to the posts. Drive the nails through the plywood into the center of the posts.

Place the ramp plywood on top of the angled posts. Secure the ramp by driving a 4-inch nail through the plywood into the center of the posts below.