Building correctly proportional steps is necessary for safety. Front porch steps, deck steps, or an outdoor stair way, all need to be designed for safe use.
If you have a project coming up that will involve building a set of steps, there are important issues to understand. We rely on steps to be comfortable to use and to be designed properly for reasons of safety. First and foremost, stairways and steps should be designed for safety. Appearance and aesthetics should be secondary concerns.
Without comfortable riser-tread proportioning, ease of use may be lessened, and without uniformity in the riser height and in the proportioning throughout the entire set of steps, safety may be lessened.
When someone places their foot on a step (whether going up or down the steps), they subconsciously expect the distance (riser height) to the next step to be the same. If it is not, the stepping rhythm of the user becomes disrupted and a serious accident may occur.
For outdoor steps, the common formula for comfortable proportioning is 2(R) + T = 26” to 27”, where R = riser height (in inches) and T = tread depth (in inches). The recommended range for riser height, in an outdoor set of steps, is a minimum of 4.5 inches to a maximum of 7 inches. The tread depth can then be obtained by using the above formula. Be sure to check your own local building code for step requirements.
A set of steps that will be used in a more relaxed or casual manner, usually in an area where space is not limited, typically uses a riser height in the lower end of the recommended range. To transgress a change in elevation more quickly or where there is limited space, a riser height at the higher end of the range is typically used.
Many times there are site constraints that need to be taken into consideration when designing and building a set of steps. One of these constraints may include a situation where the top step and the bottom step must meet up with an existing, or a specific proposed, elevation.
If this is the case, to determine the number of risers and the riser height (remember, all the riser heights in a set of steps need to be consistent), begin by measuring the overall difference of the two elevations (see sketch). For a sample calculation, say that the overall elevation difference is 29.25 inches (or 29 1/4 inches). This number (29.25 inches) must be divided by a number of risers to obtain the riser height. In your calculation, you can experiment with a different number of risers to find a riser height that falls within the recommended range. In the sample calculation, if we try 6 as the number of risers, then 29.25 inches / 6 risers = 4.875 inches (or 4 7/8 inches) for the riser height of each step. Then to obtain the tread depth, in this sample calculation, use the formula for the recommended riser-tread proportioning, 2(4.875) + T = 26” to 27”, T (tread depth) would equal 16.25” to 17.25”.
Increase the Safety of Steps
Besides having a uniform riser height and comfortable proportioning, there are other things you can do to help increase the safety of your steps. These include, but are not limited to:
– it is not recommended to use shallow risers; risers that are below the recommended minimum height may become tripping hazards
– it is not recommended to use less than 2 risers; typically a minimum of 3 risers is used
– it helps to make steps more visible; using a change in color, materials, or pattern to create a visual reference are some ways that may help from having steps that blend into their surroundings and becoming ‘invisible’
– steps where the riser board is missing, called an ‘open riser’, is not recommended; the presence of a physical riser helps to keep the user’s foot from going through the riser area; it also helps to keep small children, pets, and various objects from falling through the opening
– tread surfaces should be slip resistant