How to Build a Ramp From a Deck for Wheelchairs

Measure the height of the deck and the location of the planned end of the ramp. An ideal ramp has a slope of 1 inch for every 16 inches of distance. The maximum slope allowed is 1 inch for every 12 inches of distance. If the deck is 18 inches high, for example, the ramp would need to be 24 feet long for the ideal slope and a minimum of 18 feet long to meet Americans with Disabilities Act (ADA) requirements.

Place two stakes 2 feet apart at the planned end of the ramp. Stretch a carpenter's string from the stakes to the deck. Dig post holes 6 feet from the stakes at the end of the planned ramp and every 6 feet from there to the deck. Dig the holes at least 2 feet deep.

Place 4-inch by 4-inch posts in the holes, and use a level to set the posts upright in the holes. Cut the posts so the top is 1 inch below the string. Fill the holes with the soil you removed from the holes in Step 2, and tamp it solid.

Place a 2-inch by 8-inch stringer from the deck to the ground along the string. Cut the board at an angle to fit to the deck frame. Cut the other end with a angle to accommodate the slope as the board contacts the ground.

Nail the stringer to the posts with 16d nails or 3-inch galvanized deck screws. If you're using multiple pieces of stringer, cut the boards to end on a post.

Cut 2-inch by 6-inch treated boards to 3-foot lengths. Cut two boards for each foot of ramp length. Nail the boards to the stringers, with 6 inches extending from each side of the stringers. Use 16d nails. By setting the stringers under the ramp rather than at the edge, the weight of the wheelchair will be directly over the stringers, thus lowering the strain on the components.

Add a railing to the outside of the ramp. Use a railing similar to the railing on the deck for a unified look. Anchor the railing to the deck railing at the top with uprights attached to the edge of the ramp deck.