When I first start talking to people who may need a wheelchair ramp, they always ask how long does it have to be. This is a great question, with several different answers depending on each situation.
The golden rule will always have to deal with your local code. In general terms, there is commercial and residental code. This code refers to the slope of the ramp. Slope is how steep your ramp is in a ratio form. For instance, if your door threshold is 12 inches higher than where you want to end your ramp, a 12′ ramp would give you a 1:12 ratio.
Commercial code is 1:12, meaning for every inch of rise you have, you need 12″ of ramp. Residental code is 1:8 , meaning every inch of rise you have, you need at least 8″ of ramp surface. When I first talk to clients on the phone I ask them how many steps do they have at the site of the future ramp. Normally steps are about 7″ in height, so if the client has 3 steps, I figure about 21″ of rise. Commercial code would dictate that you would need a 21′ ramp while residental code would stipulate a 14′ ramp.
Sometimes people confuse ADA guidelines with city or county code. ADA guidelines are the same as commercial code 1:12. This is the best case scenario since it is the least steep and most people will be able to manually wheel themselves up the ramp. But people might have 8 steps or 56″ of rise, meaning a 56 foot ramp at their front door. This might not be possible due to limited space in your yard. With the residental code of 1:8, you could build a 37′ ramp.
Another question is if a building permit will be needed. In Oregon, you do not need a building permit if your project is under 30″ in height. If your project is over 30″ in height you will need a building permit, as well as handrail 36″ tall with pickets that are spaced less than four inches apart.
There are other factors to consider such as you need a level landing at the begining and ending of your ramp. The reason for this is that when you reach your front door at the end of the ramp, you need a level landing so that you can safely stop, get out your keys and unlock your front door. Also, you can not have more than 30 feet of ramp with out a level landing for a resting place.
There are many things to consider before building your ramp, and I have just touched on the very basics here. In the future I will talk about ramp surface materials, handrailing, sidewalks and other things to consider before making your home accessible.