Building a one-step wooden wheelchair ramp
Measure the height of your step. ADA minimum specs for a ramp is 1:12 (for every inch of height there must be 12 inches of length) with at least 36 inches of width available at the top of the step. Based on a standard 1:12 slope and step measuring 6 inches height, allot at least 72 inches length and 40 inches width (handrails included) for your ramp.
Visualize the product. Measure and make markings where the various parts of the ramp including the base posts should be. After making your calculations, attach a 2x4 board slightly below the stair riser. This is where the top of the ramp will rest.
Construct the posts. Dig holes and cut the posts such that they are 24 inches below the ground level and extend 36 inches vertically above the surface of the ramp. Use 4 x 4 boards to erect the posts and pour concrete into the space around the posts to make them intact.
Make a strong base. After the posts, place vertical 4 x 4 pillars at 16 inch intervals along the ramp sides, between the increasing gradient and the ground. Along the gradient, construct the ramp's base using 2 x 4 floor boards screwed onto the support pillars in a ladder-like pattern across the width.
Create the ramp. Cut a piece of plywood or lumber 72 x 40 inches (using 1:12 ratio, 6 inches x 12 = 72 inches.) Lay the top of the 72-inch plank onto the 2 x 4 board previously attached under the stair riser (step 2.) Screw it onto its "ladder" floor base and cut notches out to fit between the bottom posts.
Attach the handrails. Extend each pillar on top of the ramp so that the wooden handrails can be screwed on and aligned from the bottom post along the entire ramp length.
Finish up the project. Secure the ends of the ramp with heavy wood screws. Sand, seal and varnish wood. Add a metal threshold to prevent chipping of the wood and rubber grips to prevent slipping.