Wheelchair ramps have become a necessity for many households as people are living longer, but their mobility decreases. If a member of your family needs a wheelchair ramp to get around, there are important factors to consider. First, if the person can manoeuvre using a walker or a cane, consider replacing the current staircase with a long-tread, low rise version. If a ramp is inevitable, consider putting the ramp in a location other than over the existing staircase, for the benefit of the more mobile members of the family. Finally, the slope of the ramp is the most important element of the building process, since you don't want to cause harm to the wheelchair-bound person by making the slope too steep.
Measure the distance from the exit door to the ground to determine the slope of the ramp. If the ground varies in height, take into account the ground level where the ramp will eventually exit. Multiply the height of rise by the ratio of slope you want (Ideal is 1 cm of slope for every 20 cm of ramp (or 1 inch of slope for every 20 inches of ramp). For example, if you have 75 cm (30-inches from the exit door to the ground you would multiply that by 20, finding that you need 1500 cm (600-inches) of ramp, or 15 metres (50-feet) of horizontal projection. You can decrease the ratio to 1 cm every 12 cm (or 1-inch for every 12-inches) of ramp, but less than that is not advised.
Draw a scale version of the ramp, including a top landing of a minimum surface of 1.5 by 1.5 metres (60- by 60-inches), and a bottom landing of at least the same size. If building a switchback ramp, you will need to include a landing every time there is a change in direction, with enough room to manoeuvre. Plan on the ramp being at least 90 cm (36-inches) in width.
Build a level frame for the top landing. Cut 5 by 15 cm (2-by-6-inch) pressure-treated wood to form a box frame. Working on a level surface, mark off every 35 cm (14-inches) on centre, and nail up joist hangers at the marks, using joist hanger nails. Cut the joists to size and fit the joists into the joist hangers. Nail or screw them the end pieces of the frame. Drill three holes in each end piece, one at the centre and the other two 15 cm (6-inches) from either end. Bolt one end to the house directly underneath the entry, using carriage bolts.
Lay out posts every 1.5 to 2.1 metres (5 to 7 feet) on either side of the steps you'll be covering, to form the ramp. Using a post-hole digger, dig holes for each post. Make certain the hole is deeper than the frost line, to prevent the post from heaving during the freezing and thawing of the ground. Pour 15 cm (6-inches) of gravel into the hole and insert the pressure-treated 10 by 10 cm by 2.40 metre (4-by-4-inch by 8-foot) post. Mix concrete and water, following the manufacturer's directions and pour concrete mix into the hole, stopping just a few inches below the surface. Check for plumb--straight up and down--several times while the concrete is setting up.
Attach beams of pressure-treated 5 by 10 cm (2-by-4-inch) boards between the posts to form a perimeter of the ramp. Install joist hangers onto these boards and nail in 5 by 10 cm (2-by-4-inch) joists. Attach the ramp to the top landing with carriage bolts.
Add decking to the ramp, screwing each piece into place, forming the ramp's top surface.
Build a bottom landing, at least 60 square inches, in the same manner as the top landing, and attach to the bottom of the ramp using carriage bolts.
Measure up 90 cm (34 1/2-inches) from the decking, and attach protective railings to either side of the ramp. Pre-build the railings to fit between the posts, using pressure-treated 5 by 10 cm (2-by-4 inches) boards and 2.5 by 2.5 cm (1-by-1-inch) rails, making sure the individual rails are close together. Screw these panels to the posts leaving an opening between the railing and the ramp, then cut the post top to match the height of the railing.
Add bump boards to the edges of the ramp. Using 1.25 by 5 cm (1/2-inch by 2-inch) wide boards, attach these pieces along the edges of the ramp on both sides, to prevent chair wheels from slipping off the ramp. Add a handrail to the railing, using spacers made from scrap 2.5 by 2.5 cm (1-by-1 inch) pieces of wood. This is particularly useful when a person is pulling himself up the ramp. Make certain the railing is secure.