Awhile back a friend and I were chatting about his basement reno and how he was installing new stairs. He was switching from two sets of stairs and a landing to one long flight of stairs. He asked me how many steps were in a flight of stairs.
In a typical home with 8-foot walls, a flight of stairs has between 13 – 15 steps. A home with 9’ ceilings will require 15 – 17 steps. Homes with 10’ ceilings will need 17 – 19 steps. A maximum rise of 7 ¾” per step is permissible, according to the IRC.
It is important to remember that a flight of stairs is one unbroken set of stairs. Stairs that have a landing, then continue down at a 90-degree angle in an L-shape are not considered a “flight” of stairs.
In this article, we’ll dig deeper and talk about typical lengths and heights of a standard set of stairs. There is no standard number of stairs required by code. On the other hand, some regulations must be followed in terms of stair rise and run. These give us a clear idea of the number of steps you’ll need in a flight.
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What is a Flight of Stairs?
A flight of stairs is a set of stairs that is not interrupted by a landing or any other feature. It is a run of treads of the same rise and run. Flights do not require certain amounts of steps, but they do have to have steps that are evenly spaced without a break.
One flight of stairs is a length of stairs that is not broken up by a landing. There is no minimum or maximum length or number of steps. One flight can be curved, spiral, or straight. All steps in a flight are of the uniform rise and run per tread.
Flight of Stairs Definition
A flight of stairs, by definition, is a set of stairs of the same rise and run per tread, without a landing or any other feature that interrupts the stairs. A flight of stairs can be any type or style as long as it is uniform and uninterrupted.
The phrase “flight of stairs” derives from, to the best of our knowledge, an old French phrase that meant “to fly up stairs” going back hundreds of years. The word “flight” indicates that one can ascend or descend stairs quickly without interruption.
There is sometimes confusion regarding stairs and steps, as we don’t say “flight of steps”. Steps refer to either a single step on a flight of stairs or are more commonly used to reference outdoor stairs. When referring to a set of steps indoors, we use the term “stairs”.
Benefits of a Flight of Stairs
One flight of stairs can save space in a house and can also be visually appealing to the aesthetic of the house, as long, straight lines make for pleasing sightlines in a space.
It is standard for homes to have either between 8’ and 10’ ceilings, with 8’ being the most common. Unless you have a split-level home, dwellings with ceilings of these heights will almost always have at least one flight of stairs.
Flights of stairs are more common simply because there isn’t the space to have a landing in a traditional home, and there isn’t a necessity. While long staircases may need landings due to space constraints, these are often only found in structures with more distance between floors.
While one straight run – or flight – of stairs might be desirable, it just might not be possible in your house. You may have to use a landing, and if so, you would then have two separate “flights” of stairs instead of one.
A flight of stairs can be a showpiece in your home, particularly if you opt for floating stairs or nicely finished hardwood treads. The uniform aesthetic combined with unique finish details can make a flight of stairs a showpiece. Breaking up a nicely finished flight of stairs with a landing does not have a unique aesthetic.
How Many Steps In A Flight Of Stairs?
A flight of stairs in a home with 8’ ceilings will have 14 steps if the rise of each step is 7 ¾”. If ceilings are 9’, then a flight of stairs will have 16 steps with the same stair rise height. 10’ ceilings will have 17 steps.
There are several ways to calculate the number of steps you’ll need, but the simplest is to take the total ceiling height, including the width of the joists supporting the floor above and the thickness of the subfloor.
Number of Steps for 8’ Ceilings
For example, your home has 8’ ceilings, with 10” wide joists supporting the floor above. 10” wide joists are 9 ¼” wide. You also have 3/4” subfloor on top of those joists. Therefore the total rise from the bottom to the top floor of your flight of stairs is 8’ 10”. Convert that total into inches to get 106”.
We’ll use the maximum allowed stair rise per the IRC which is 7 ¾”. Divide 106” by 7.75 and you get 13.7. Therefore, you will need 14 steps.
Divide 106” by 14 to find the rise per each step and you get 7.6, or about 7 9/16” rise per step.
Number of Steps for 9’ Ceilings
For homes with 9’ ceilings, your total rise for a flight of stairs will be 118”, using the same dimensions for the joists and subfloor as the previous example.
Divide 118” by 7 ¾” and you get 15.2. With stairs, you cannot simply round down to 15 if you want fewer steps. If you did that, then you’d end up with a final step of about 4”, which would be awkward and dangerous. You have to round up and adjust the rise of each step accordingly.
A flight of stairs for homes with 9’ ceilings will need 16 steps. To find out the rise of each step, divide 118” by 16. You get 7.4 inches, which is nearly 7 7/16”. Thus, you end up with 16 steps at just under 7 ½” high per step.
Number of Steps for 10’ Ceilings
Using the same dimensions as above, with 10” wide joists and 3/4” subfloor, then you end up with a total rise of 130”. Divide it by 7 ¾” and you get 16.8 – which means you’ll need 17 steps.
A flight of stairs in a home with 10’ ceilings will require 17 steps, minimum. To find the rise of each step, divide 130” by 17. Each step will be about 7.7” high, or 7 11/16” high.
What Is the Minimum Number of Steps in One Flight?
One flight of stairs has no specific definition beyond an unbroken set of stairs without a landing or other interruption. Therefore, there is no explicit minimum number of steps in one flight of stairs according to the building code.
The building code states that the maximum riser height is 7.75”, which ensures you have enough steps for a safe flight of stairs. Knowing this number, we can figure out a minimum number of steps allowed for one flight of stairs.
For example, the IRC dictates that there cannot be more than 12’ of vertical rise between floors or landings. Therefore, for that distance, what is the minimum number of steps you can have? Let’s calculate.
To calculate the minimum number of stairs for a vertical rise of 12’, first convert 12’ into inches – 144”. Then, divide 144” by 7.75”, which equals 18.5.
Therefore, you cannot have less than 19 steps for a 12’ vertical rise. After 19 steps, the stairs must terminate at the next floor, or you must have a landing before steps can continue.
For any other vertical span, such as 9’ or 10’, convert to inches and divide by 7.75 to determine the minimum number of steps for that vertical span.
Maximum Number of Steps in a Flight of Stairs
There is a maximum number of steps per flight of stairs. According to the IBC, the minimum riser height is 4”. A riser any shorter than 4” can risk the safety of those using the stairs; therefore we keep risers between 4” and 7 ¾”.
To determine the maximum number of steps in a flight of stairs, we’ll use a 12’ vertical rise to determine the max amount of steps allowed for that amount of height.
First, we’ll convert 12’ to inches, which is 144”. Next, we’ll divide 144” by 4”, and we get 36. Therefore, the maximum amount of steps you are allowed for a flight of stairs spanning a 12’ vertical distance is 36 steps.
How Long is a Flight of Stairs?
The length of stairs can vary widely since tread depths often see a wider variance than riser height. Since vertical drop is more of a safety concern per step than tread depth, builders and DIYers often manipulate tread depth to fit horizontal space.
The minimum tread depth of a residential step is 10”. Each tread must have a nosing that is at least ¾” beyond the front edge of the step and no more than 1 ½”. There is no maximum tread length.
Calculating the length of a flight of stairs involves knowing the depth of your tread and the length of the stair tread nosing. Minimum tread nosing is ¾”. Thus, if you have 10” treads, subtract ¾” for true horizontal span – so, 9.25”
Length of Staircase for 8-Foot Ceiling
A home with 8’ ceilings requires 14 steps, at a minimum. Multiply 14 and 9.25 and you get 130” of horizontal run. A tread depth of 10” plus a nosing would result in a length of around 140”, which is a common length for stairs in a home with 8’ ceilings.
The standard size of stairs for a stair rise and tread on a flight of residential stairs is 7”/11”, or 7” of rise by 11” of run. Stairs with treads of 11” in a home with 8’ ceilings would have a total length of 154”.
How Long Is a Staircase for 9 Foot Ceilings?
A flight of stairs in a home with 9’ ceilings requires 16 steps. If each tread is 11” deep, then the total length of the staircase will be 176”. A tread depth of 10” will result in a minimum length of 160”.
Length of Staircase for a 10 Foot Ceiling
A staircase in a home with 10’ ceilings requires 17 steps. Stairs that have a tread depth of 11” will have a total length of 187”. Stairs with a tread depth of 10” will have a total length of 170”, which is the minimum length.
Maximum Length of a Flight of Stairs
There is no maximum length for a flight of stairs, as the building code does not state a minimum riser height. However, you cannot have a flight of stairs that spans more than 12’ in vertical length.
Secondly, a flight of stairs must terminate in a landing that is at least 36” long. Therefore, a flight of steps cannot span the entirety of a wall, as room must be given for the stairs to terminate. So your stairs are constrained by the overall dimensions of the home and code restrictions for stair landings.
How Tall is a Flight of Stairs?
A flight of stairs is usually the height of the ceiling plus the framing and subfloor of the floor above where the stairs terminate. In a space with 8’ ceilings, a flight of stairs is anywhere from 8’ 8” to just over 9’ high.
Homes with ceilings that are 9’ or 10’ will have stairs that are either 10’ or 11’, respectively. Again, the actual height depends on the floor framing and, to a lesser extent, the subfloor on the top floor.
To calculate stair height, take the ceiling height and add the width of the joists that frame the floor where the height of the stairs terminate. Typically this is either 8”, 10”, or 12” dimensional lumber. Then you have to add the thickness of the subfloor – normally between ½” and ¾”.
Most stairs are framed during construction and are calculated without the finish floor in place, which is why we only calculate the subfloor in our calculations.
The landing at the top of a flight of stairs does not count as a stair “tread”. There is always one more riser than stair tread because a flight of stairs begins with a riser and ends with a riser.
When considering the number of steps in a flight of stairs, remember that knowing your local building code is crucial. Universal building code states that 10” is the minimum tread depth and 7 ¾” is the maximum riser height. Knowing these measurements is a great start in building a safe, code-compliant flight of stairs.
You have lots of options when it comes to varying your flight of stairs. You can use an L-shape design with landings or a spiral staircase to maximize space. If choosing a spiral staircase, remember they have an extra set of code standards you must follow.
I wish you luck with your next stair project. Remember to always work safely and measure twice. If you still aren’t sure, then consult a professional – happy building!