What Is the Difference Between a Stair Tread & a Stair Riser?

Tread

• The tread on each stair is the horizontal area where you place your foot as you ascend the steps. One way to remember the tread is that the tread of your shoes stands on the tread of the stairs. Usually, the tread should be at least 9 inches deep, but check with your local building codes to verify the number. A tread that is too narrow prevents a person from fully planting his foot on the stair and could result in tripping. Treads on stairs that are too wide require a second step to make it to the next stair, requiring excess energy to climb.

Riser

• The riser is the vertical portion of each step. The distance between the treads on the stairs determines the height of the riser, but not all stairs have risers. Some stairs, such as those used outside or in utility spaces, do not have a board between the treads. Since you can see between the treads to the space under the stairs, these riser-less steps are known as open tread. Closed tread stairs have risers included. Generally, codes require a maximum height for risers around 8 inches to make climbing easier, but this can vary by your area. Check the local building codes on stair riser heights if you are building your own staircase.

Riser Calculations

• Careful measurements of the area where the stairs will go will help you to determine the number of steps you need based on the size of the risers and treads required by your local code. Use a plumb line to measure from the floor of the second floor to the floor of the first floor. Divide this number in inches by the code requirement for maximum stair height to determine the number of risers needed. Round the number up to the nearest whole number. Divide the total height by the number of risers needed to find the actual height of the risers you will need.

Tread Calculations

• The depth of the stairs is tied to the height of the risers on each step. A rule of thumb to use when calculating the tread depth is to subtract the riser height from 17 or 18 to find the tread depth. For instance, if your stairs have a riser height of 7-1/2 inches, the tread depth can be between 9-1/2 and 10-1/2 inches. Multiply the tread depth by the number of risers to determine the total distance you will need for the stairs for a straight run. Subtract one tread length to compensate for the floor at the bottom of the stairs to find the actual distance needed for all of the stair treads.