Basement Stairway Size Requirements

In this article we will be discussing the many size requirements for building your basement stairway. First of all we will mention some common terminology of stairways. The basic components are going to be the following:

    • Steps: composed of the riser and the tread.
    • Riser: the board that runs vertically to make the height of the step.
    • Tread: the board that makes the stepping surface of the step.
    • Nosing; the edge of the tread that protrudes over the underlying riser.
    • Stringer board: sometimes referred as just the stringer or string, it is the stair shaped, often precut board that supports the treads and risers. One goes on the right and one on the left of the stairway.
    • Headroom: the height from the tip of the nosing on a tread to the ceiling above.
    • Banister: the handrail or a rail that runs up the length of the stairway that is used as a hand grip.
    • Balusters: the vertical bars that hold up the Banister.
    • Newel post: The post at the foot or head of the stairs that supports the banister.

Here we give the most common sizing standards for basement staircases. The actual building codes may vary slightly from place to place. The best thing to do is contact your local building code specialist to make sure the measurements are safe for your area.

Basic Measurements for Typical Basement Staircase

Basement StaircaseStringers used to be a complexity, but these days, almost all builders use precut stringers eliminating the need to do tricky cuts. Of course, it is essential that you choose your stringers first and then calculate your tread and riser heights so they will all work together. However, if you purchase a precut stringer, you do not have much choice as to the size.

If you want to make your own stringer, this can be done with careful measuring. The smallest size board you can use is a 2x10 and you should allow for a minimum of 3-½ inches of solid uncut board on the opposite side of the cuts. A 2x12 is often needed. You will need both a framing square and a set of stair gages to accurately measure the cuts. Simply clamp the stair gages onto the framing square at the correct measurement marks for your tread and rise.

To figure these measurements:

    1. Figure your total run or rise by measuring the distance from the first floor to the basement floor.

    2. Take the total run and divide it by the height that you want your rise to be. This tells you how many steps. If you have a 91inch total rise and want a 7 inch rise, you divide 91 by 7 and get 13 rises. The number of steps is going to be 1 less than the number of rises, so we would have 12 steps. You will usually have to play with the size of your risers and number of steps to get a nicely proportioned stairway.

Steps and Treads

Most steps have a riser height of about 7 inches. The minimum riser height can be as little as 4 inches and the maximum height is usually 8 inches. I have seen variances of this code.

Some areas have building code that specifies a minimum of 5 inches and a max of 8.25, so to be safe, you should reference your local code. You can generally select a riser height within the 7 inch area and be safe though.

The tread depth is usually about 10 or 11 inches. Tread depth is measured from the tip of the nosing of one tread to the tip if the nosing of the next tread. The minimum tread depth is usually 9 inches in most areas. There generally is no maximum tread depth as they are generally safer the deeper they are.

Variances on the sizes of treads and risers should be very little because people climbing a long set of stairs get used to stepping a particular way and if there are variances, it will cause accidental trips and falls. Most building codes require that there be no more than a 3/8 inch difference from the smallest tread or riser to the largest.

The headroom should normally be about 7 feet. The minimum headroom to meet code in most places is 6 feet, 8 inches from the tip if the tread to the ceiling.

Banister Requirements

There are also several requirements for the handrails on your basement stairs as well. Firstly, most local codes require one handrail on stairways with 4 or more risers. Banisters usually need to be from 34 to 38 inches high as dictated by standard code.

Your Banister should run the entire length of the stairs and has to end in a newel post or a safety terminal. A cross section of the banister should measure between 1-¼ and 2-5/8 inches to comply to code. Balusters should be less than 4 inches apart.

All balusters should be strictly vertical with no ornamental horizontal connectors. Patterns that provide a ladder like effect on the balusters are prohibited in finished basements.

Photo by ignote, Creative Commons Attribution License