If you own a business, it just makes good sense to make it accessible to everyone. Turning away potential income is not a good business practice. Not only that, but if you are not accessible to the disabled you risk the possibility of a lawsuit. The ADA (Americans with Disabilities Act) was passed in 1990. Section 4.8 deals with mobility ramps. The following specs for mobility ramps are taken from the ADA Accessibility Guidelines as amended through September 2002. If you would like to see the entire document I've provided a link below.
The ADA states that any part of an accessible route that has a slope steeper than 1:20 (20 inches of length for every 1 inch of rise) is considered a ramp. If you do not have an elevator you need to provide mobility ramps to allow access to the different levels of your building. You should always use the least amount of slope possible for any ramp.
If you are constructing a new building the maximum amount of slope you can have for any ramp is 1:12. The maximum rise you can have for any run is 30 inches. If you have an existing site that you are constructing mobility ramps for, things change a little.
An existing building may not have the space to install ramps that meet the 1:12 slope or less. If that is the case then a slope between 1:10 and 1:12 is allowed for a maximum rise of 6 inches. A slope between 1: 8 and 1:10 is allowed for a maximum rise of 3 inches. A slope steeper than 1: 8 is not allowed.
The preferred amount of slope is between 1:16 and 1:20. The ability to manage an incline is related to both its slope and its length. Wheelchair users with disabilities affecting their arms or with low stamina have serious difficulty using ramps. Most people who use wheelchairs can manage a slope of 1:16. Many people can not manage a slope of 1:12 for a distance of 30 feet or more. The minimum width of a ramp is 36 inches and must be clear of any obstructions.
Mobility ramps need to have a landing at the top and bottom of each run. A landing is a level area to recuperate if there are any more runs to manage and allow for easy transitions if the ramp goes in another direction. Landings need to be at least as wide as the ramp leading to it. The length of the landing must be a minimum of 60 inches clear of any obstructions. If the ramp changes directions at the landings, the landing needs to be 60 inches by 60 inches minimum. Landings need to be level. A landing that is not level causes individuals using wheelchairs to tip backward or bottom out when the ramp is approached.
If a ramps has a rise more than 6 inches, then it must have handrails on both sides. However, handrails are not required on curb ramps. Handrails must extend at least 12 inches beyond the top and bottom of the ramp segment and must be parallel with the floor or ground surface. If the ramp changes directions the inside handrail must always be continuous. The handrails along any segment of the ramp can not have any gaps in them. The top of the handrail's gripping surface needs to be between 34 and 38 inches above the surface of the ramp and can not rotate in their fittings. The ends need to be rounded or returned smoothly to the floor, wall or post.
The above handrail requirements are for adults. If the ramps are mainly for children (for example in elementary schools), a second set of handrails can assist them and aid in preventing accidents. A maximum height of 28 inches to the top of the gripping surface from the ramp surface is recommended for handrails designed for children. The clearance between upper and lower handrails is 9 inches minimum.
The cross slope of ramp surfaces can not be greater than 1:50. If your ramp is 36 inches wide then both sides of the ramp must be within .24 inches in height from each other.
If your ramps and landings have drop-offs then they must have curbs, walls or railings that prevent people from slipping off the ramp. Curbs have to be a minimum of 2 inches high.
Outdoor ramps and their approaches must be designed so that water can not puddle on walking surfaces.
The above is just a brief summary of the ADA guidelines for mobility ramps. If you would like to see the document in its entirety click here [http://www.access-board.gov/adaag/html/adaag.htm#4.8]. Section 4.8 has many links to other sections of the document inside of it. To cover everything would be outside of the scope of this article. I highly recommend you read the entire document and all of its links before starting any mobility ramp project. It will only cost you a little bit of your time and can save many headaches down the road.