Buying a new staircase: What are the minimum and maximum widths?

Sizes and measurements are key questions to figure out when buying a staircase – this guide will help you to quickly make the right decisions:

There are many factors to take into account when purchasing a new staircase. In terms of staircase dimensions, these are determined by your local city department and must be adhered to so that your staircase is as safe as possible for users. 

These pre-determined sizes vary from department to department and it is a good idea to check this with your local authorities before commencing as this is a vital step if you wish to have your staircase pass inspection. 

In this article, we will discuss the code requirements for a straight-style staircase. Note that a spiral or winding staircase will be subject to different code requirements. 

Width requirements. 

Staircases have a minimum width requirement for a reason: so that users can climb up and down with ease and in a safe way. Meeting this requirement helps to avoid falls and facilitates the movement of users down the stairs in the case of a fire. The minimum, side-to-side distance for a staircase should be 36 inches, excluding handrails. 

Maximum riser height. 

Stair risers refer to the back and vertical portion of your step and the riser height would therefore be the distance measured when stepping from one step to another. The stair riser height should not be higher than 7 3/4 inches. 

Stair risers that conform to local code specifications ensure that your stairs are not too high for users when climbing or descending. To avoid possible falling or tripping, it is suggested that each riser height be identical. The maximum suggested difference between riser heights should not exceed 3/8 of an inch. 

In the case of open risers (or gaps between stairs), there should be sufficient space for a 4 inch object to pass through. A little less than a 4 inch space is therefore the most suitable. 

Minimum staircase tread. 

Staircase tread can be described as the linear distance between the nose (or front edge) of each step to the back section where it is connected to the stair riser. The depth of your staircase tread should be a minimum of 10 inches. This is applicable if your staircase consists of nosings that overlap the underlying risers. If your stairs do not have nosings and your risers are solid (with no open gaps), there is a minimum tread depth requirement of 11 inches. 

It is very important to have risers that are deep enough so that a user’s foot has sufficient room in which to rest upon the step. This is an important safety aspect, especially when descending the staircase. 

To avoid any potential falling or tripping, tread depths should be as identical as possible. Most city departments require there to be no more than 3/8 of an inch difference between the biggest and smallest tread depth. 

The staircase nosing is also another vital element to get right. These should be projected at least 3/4 of an inch with a maximum protrusion of 11/4 inches above the riser underneath. The maximum difference in projection measurement for nosings should not exceed 3/8 of an inch. 

Minimum staircase headroom height. 

When using your staircase, users should have at least a 6 foot and 8 inches vertical space in which to stand. This measurement is taken from the bottom of the ceiling and down to the top portion of your stair tread. 

Having enough vertical room in which to use the staircase is essential to avoid the user hitting their head on the ceiling. When a staircase user is forced to concentrate on avoiding hitting their head, this causes distraction which can, in turn, also lead to a fall. 

Minimum depth measurement for landings. 

It goes without saying that you need to have a landing at both the top and the bottom of your staircase. Your staircase landing is also subject to minimum depth requirements in that it should measure at least 36 inches. This measurement should be taken perpendicular to the direction of traveling up or down the stairs. 

Lighting. 

Lighting allows staircase users to detect any potential hazards and to travel up or down safely. Your artificial light source should illuminate your top and bottom landings, as well as each tread and should not be dimmer than 11 lux. If your staircase has more than six risers, you will need to provide a light switch on the walls on the ground floor and at the top of the stairs.

Adhering to your local city codes in terms of minimum and maximum measurements can be cumbersome but this will ensure that your stairs are as safe as possible.