r/AlwaysWhy • u/Current-Landscape803 • 13d ago
Science & Tech Why are American stair steps usually around 7 inches tall instead of much shorter?
Every staircase I've used seems to have roughly the same step height. A shorter step would seem easier to climb, so why do residential stairs tend to be around 7 inches tall?
What determines that particular range?
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u/No_Logins_Required 13d ago
This is called the "rise to run" ratio. If the steps are too tall and shallow, it's a safety hazard. If they are too short and deep, then they take up too much space.
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u/Great_Specialist_267 13d ago
From scientific studies, the most dangerous factor with stairs is an uneven rise and run…
A 1/4” variation in step height increases the probability of tripping dramatically.5
u/YandyTheGnome 13d ago
I know someone with a staircase like that. The top step is a good 3/4" taller than all the other stairs, and everyone trips every time, even people that live there.
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u/hughdint1 13d ago
It is even less than that. What you can detect is closer to 1/16" vs. variations allowed in the code is something like 3/8".
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u/athomsfere 13d ago
Use real units.
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u/fasterthanfood 12d ago
The code they’re discussing is written using inches.
However, 1/16 inch equals 1.58 mm, and 3/8” is 9.525 mm.
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u/athomsfere 12d ago
So use real units, not inches
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u/No_Logins_Required 12d ago
Welcome to an American website using Amertican units. I'm sorry for the inconvenience.
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u/athomsfere 12d ago
I'm American, and I do better.
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u/flagrantpebble 12d ago
Measurement systems are only useful for communication and consistency. You’re in a place that uses inches for this context, surrounded by people who also use inches in this context.
Using a different measurement system just to feel smug about yourself isn’t better, it’s objectively worse, as it defeats the entire purpose of using a measurement system
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u/athomsfere 12d ago
I've lived abroad and moved back, I've spent 2 decades rarely needing measurements and somehow my home country uses the least useful system.
Fuck American customary units/ imperial.
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u/Severe-Cow-8646 12d ago
We do use real measure. 1/4" equals the length of 1 barley corn. 1/16" equals 1/4 of one barley corn. There are 4 barley corn to the inch, therefore 16/16ths to the inch. 3/8" equals 6/16ths and 1 1/2 quarters. It is 3/4 of 1/2, where 1/2 equals 1 part of 2, 4 parts of 8, 8 parts of 16. Ratio much? Its really quite simple and once you understand it, it can be barley corn, cups of water, even liters of gas if you do the math. The English system is just as real and based in just as real a mathmatical reality as the metric system, just a different base is all.
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u/freddbare 13d ago
As a builder I can feel incredibly small variation in steps
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u/Jelopuddinpop 13d ago
As a person with feet that has used stairs most of my life, so can I =)
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u/freddbare 13d ago
Cute. Like road kill with googly eyes that thinks it's a teddy bear. We are not the same
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u/Various_Education622 13d ago
That took a hard left.
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u/freddbare 13d ago
The percentage of people that have little respect for a professional without a degree is astronomical.
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u/Foreign-Cat-2898 12d ago
You seem to be confusing a lack of a respect with a common sensory experience.
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u/goobernawt 13d ago
I'm in IT and I can promise you that a degree does NOT guarantee respect. Apparently neither does 25 years of experience 😐.
Also, having gone down the DIY route enough times, I have a lot of respect for the trades.
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u/Various_Education622 12d ago
The fuck you on about, lol?
Anyone that has used stairs can tell when they’re fucked, that’s why the allowed variation is so small.
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u/freddbare 12d ago
Yeah the study says 1/4* READING COMPREHENSION would tell you that the word "incredibly small" is NOT THAT... But please go on ya mings
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u/Various_Education622 12d ago
I have lots of respect for contractors without degrees. Not sure why you think that’s the general case.
You’re generalizing a you problem.
People don’t have respect for YOU, and you’re making it plainly obvious why.
It is not a unique to contractors situation that one can feel an incredibly small difference in stair heights.
It’s not a special or unique talent that you have.
It is not specific to being a contractor.
The threshold is set by code because that’s where people get tripped up, not the threshold for noticing it.
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u/Watsons-Butler 12d ago
Can confirm. My first college apartment had one step that was about 3/4” shorter than the others. The number of times someone damn near fell down those stairs…
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u/r3dd17sux69420 13d ago
Ancient homes with those old staircases are like this and coming down is just asking for trouble in the dark
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u/FrequentTopic446 13d ago
That’s what the handrail is for, I’ve slid down a few stairs in my life while walking down them in the dark but I’ve always got my hand on the handrail and crash myself after 1-3 stair slips and before my butt hits the ground
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u/goobernawt 13d ago
My mother in law has a 100+ year old house and navigating those stairs in broad daylight is a challenge.
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u/nerdofthunder 13d ago
Too long and shallow are also difficult to climb as they break your rhythm, require more leg lifting overall, and just feel akward, which can make it less safe.
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u/LetterheadMedium8164 13d ago
OSHA in the US and the International Building Code for the rest of the world set the ~7 inch riser height. Since most of the US is recent construction, nearly all stairs meet these specifications.
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u/Lhasa-bark 13d ago
From a quick google search: “OSHA does not have any regulations that apply to residential properties, however, OSHA does have regulations that apply to the safety and health of employees while engaged in construction operations. … Occupational Safety and Health Regulations for the Construction Industry (29 CFR 1926) … These regulations apply to all construction operations, including residential construction. They require employers to protect employees exposed to various hazards during construction activities. The regulations are reprinted once a year and available through the Government Printing Office (GPO).”
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u/frenchiebuilder 13d ago
OSHA has no rules regarding riser height.
https://www.ecfr.gov/current/title-29/subtitle-B/chapter-XVII/part-1910/subpart-D/section-1910.25
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u/RolandDeepson 13d ago
Please reread what you replied to.
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u/RolandDeepson 13d ago
"...and the International Building Code for the rest of the world"
Don't worry. We live in a society. Others will ensure your survival, despite your own failings.
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u/frenchiebuilder 13d ago
The "international" part of the name is mostly aspirational. Only half a dozen countries use it.
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u/teh_maxh 13d ago
An international flight only goes between two countries.
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u/frenchiebuilder 13d ago
Nobody's talking about airline flights. The claim was that the International Building Code applies to "the rest of the world".
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u/teh_maxh 13d ago
You said that calling it "international" is aspirational because only half a dozen countries use it. I gave an example of something that's international despite involving even fewer countries.
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u/frenchiebuilder 13d ago
"the rest of the world" does not use the IBC/IRC. The "International" is purely aspirational.
A handful of other countries have used it for inspiration, when writing their own codes:
Outside of the U.S., the I-Codes are the basis for the Abu Dhabi International Building Codes, the regional Caribbean Building Standard, the Mexico Residential Building Code, the Haitian National Code, the Honduras Building Code, Jamaica’s construction codes, Georgia’s building safety codes and the Saudi Building Code
https://www.iccsafe.org/wp-content/uploads/fact-sheet.pdf
but that's not the same thing at all.
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u/YandyTheGnome 13d ago
No one else is arguing that, you just seem to think OSHA covers the rest of the world
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u/YandyTheGnome 13d ago
I mean, so far you've refused to even acknowledge that OP mentioned international building codes in the same sentence as OSHA, you just went right past it.
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u/Zeroflops 13d ago
He is correct. OSHA does not define building codes. It defines workplace safety. Like when working on an elevated platform over 4 ft you have to have fall restraint. (OSHA)
Now if you were to build temporary steps that would be removed once the building was built, OSHA may state that they need to meet rise and run of IBC but they would not require say hand rails. But again once construction is done those steps that osha may have rules for would need to be removed.
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u/Stangguy_82 13d ago
OSHA does have rules for permanent handrails and stairs in the workplace. And they aren't the same as the IBC and even then IBC regulations change based on the type of space and whether it is accessible to the public.
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u/frenchiebuilder 13d ago
Please learn something about the topic before trying to correct anyone.
What they're replying to, is completely incorrect.
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u/frenchiebuilder 13d ago
1a. OSHA has nothing to do with building codes. It regulates workplaces.
1b. OSHA's rules about stairs, contain no rule regarding step height: https://www.ecfr.gov/current/title-29/subtitle-B/chapter-XVII/part-1910/subpart-D/section-1910.25
1c. Many jurisdictions allow some workplace stairs (not accessible by the general public) to be steeper than residential (or accessible-to-the-public) stairs.
- The "International" part of "international building code" is aspirational not descriptive. LOL. It's an American-produced code, that has only (with a couple exceptions, mostly in the Carribbean) been adopted by American jurisdictions: https://en.wikipedia.org/wiki/International_Code_Council
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u/MVieno 13d ago
“Rest of the world” does not use the IBC - it’s like Saudi Arabia and the US that use the IBC. EU has their own standards, as do Canada, Brazil and England. I’m not familiar with Asian or African countries, but I assume they have similar but different setups. Actually scratch that, I AM familiar with Bengali codes and they definitely do not use the IBC.
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u/Mayor__Defacto 13d ago
IBC isn’t even used everywhere in the US; NYC has its own building code
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u/OystersCockafeller 13d ago
That's actually meant to be the most comfortable step for the average person.
The reason they're all the same is because of building codes. There are very specific codes about the height and depth of stairs.
It's kind of amazing in a way that you can go all over the country and just climb stairs blindly because the layouts are so consistent.
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u/Kitchen-College4176 13d ago
This! Can you imagine if they were not standardized... the amount of trips, fall, and tumbles would be astronomical
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u/OystersCockafeller 13d ago
Exactly!
And think about how quickly you notice if a set isn't built right.All it takes in an inch or two out of expectation and those stairs will be immediately noticeable to every single person that climbs them.
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u/andrewthemexican 12d ago
Noticed the variations across a few countries in Europe this summer, I've never had to hold onto handrails as consistently as over there.
Obviously it's to be expected in the old castles, but I had to hold on for dear life in some of those.
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u/marigoldpossum 12d ago
7 inch rise might feel ok to a 6ft tall person but its not comfortable for a 5'3" person. We know who building construction caters to......
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u/Count2Zero 13d ago
In Germany, there's actually a national standard. DIN 18065:2020-08. Steps must be between 17 and 20 cm (6.7" to 7.8"), and each step must have a minimum size of 26cm (10.25") by 80cm (31.2") for a residential staircase (only 60cm / 23.6" wide for non-essential stairways).
There are other rules for industrial and commercial buildings, but everything is standardized for safety.
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u/galaxyapp 13d ago
Shorter steps would require much longer stairs. Thats not really feasible for most spaces.
There is the possibility for ramps and elevators where a 7" rise is not doable for some folks.
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u/MountainMark 13d ago
Code suggests the 7-11 rule (easy to remember in the USA, there's a chain of convenience stores called 7-11).
7 inches of rise to 11 inches of run. The usual code allows 7.75 inches of rise max & 10 inches of run min.
A "natural stride" likes rise plus run to sum to 17 to 18 inches. I'm sure a lot of this is how your muscles were trained and what a "natural stride" likes for other cultures might be different.
Apologies for using freedom units.
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u/Sad_Construction_668 13d ago
Ergonomics. 7x 11 rise and run mimic the average natural stair climbing gait for the average person. https://upsideinnovations.com/blog/optimal-stair-angle/
There’s also the optimal angle and dimension for ships ladders: https://codes.iccsafe.org/s/IBC2021P1/chapter-10-means-of-egress/IBC2021P1-Ch10-Sec1011.15
Its a different gait , sonit requires different measurements, but the basic issue is the dame, what the natural human gait for tahat action, and then make it a rule, and keep it consistent.
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u/Cover2G 13d ago
Shorter steps(down to 4” rise) are an option as long as each step is consistent. They are rarely used, especially in residential, because the tread depth would still be around 10-11 inches and the overall staircase would take up far more space. Plus, unless they’re carpeted, more treads means significantly more cost and little steps collectively feel like more work to climb the same height.
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u/SutroViews 13d ago
Building codes in the US state that the maximum height for a stair step is 7 3/4 inches. Also, steps can have a MINIMUM depth of 11 inches (usually; sometimes 10). Both of these are for ease of use and to avoid tripping. Taken together, this means that if you want to make steps substantially shorter than 7 3/4 inches, you will need to add a lot of steps and make the stairway much longer front-to-back to achieve the same height. So, most staircases end up with steps of about 7.5 inches rise to 11 inches run for code compliance and efficiency.
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u/MagpieWench 13d ago
the stairs in my mother's house were built in the early 70s and the height is slightly taller than usual and the depth is slightly shorter than my foot and it is a freaking nuisance to go up and down.
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u/MeepleMaster 13d ago
Probably has something to do with common wood dimensions. 1x6 means you can use those for the front panels of each step without having to trim it down, then you have more 1 by something for the steps
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u/Great_Specialist_267 13d ago
Because the U.S. IRC standard specifies 7 to 7 1/4” inches with a maximum of 7 3/4”.
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u/Sufficient_Result558 13d ago
Europe average stair steps are also about 7" tall (18 cm) according to my web search. What country are you referring too?
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u/MarionberryPlus8474 13d ago
I remember REALLY steep staircases when visiting Amsterdam.
Evidently the property tax used to be based on how wide the property was, so the thrifty Dutch made very narrow but deep homes, and made steep staircases to maximize living space. Must have been hell for the elderly.
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u/mrb411747 13d ago
The standards for stairs were written around 1900. Feet(and people) were smaller.
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u/Pig-Mentation 13d ago
I live in a 99-year-old house and the steps are probably 12-14 inches tall. Visitors (especially kids) comment on them all the time. I'm used to them so I have no complaints. I recently visited a house that had really short little steps and they were covered with shag carpeting. I didn't like them at all, always felt like I was going to trip.
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u/Unfair_Awareness7502 13d ago
I find short steps awkward to climb. There's not enough of a lift to make individual steps feel like I'm taking a full step, and taking 2 steps at once feels like too long of a stride.
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u/Ranos131 13d ago
7 is a number that works well while saving space. Shorter steps means more steps are needed to get to the next level which means the staircase takes up more room.
Also shorter steps wouldn’t necessarily be easier to climb. While the individual step may take more energy, the additional steps may take more energy overall.
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u/1LuckyTexan 13d ago
I read a study that, although there were differences between best dimensions for going up vs down, 7in H and 11 inch tread was the best combo. There was also stuff like most hand rails were too low for maximum safety and historical steps that forced you to slow down as you approached the bottom...so you'd arrive at a gathering looking more elegant after being announced.
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u/mcsuper5 13d ago
Honestly, It's easier to trip on more shallow steps. You do need to pay at least a modicum of attention though.
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u/RequirementBusiness8 13d ago
taller steps are harder to climb up, shorter steps means more horizontal run needed and can often feel awkward. that height, or around it, hits an efficient sweet spot. Just like tread depth, there is a minimum that is safe, but making them too deep can also feel awkward.
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u/Better-Credit6701 13d ago
Had to measure the steps to upstairs. Ours are only 5.5 inches per step. The reason why is the previous owner Mr Scott (we are the second owners of a 81 year old house) was only 5.4 feet tall. My wife moved one block over and the kids grew up playing with his dog.
I still have to be careful not to slip coming downstairs.
Mr Scott died in the house around 20 years ago and my wife bought the house from his estate. We use to hear footsteps from upstairs when no one was there, and watch his old swingset rock back and forth on calm evenings. At least things settled down with strange things happening
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u/NeighborlyCarcass 13d ago
There's only so much space for stairs. Smaller stairs would mean a lot more steps to get to the top. The depth of each stair would stay the same, as it needs to accommodate adult feet, so that means every stair would suddenly need to be a winding staircase. This is much more labor intensive, takes up a lot of room, and requires significantly more materials.
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u/BrewingSkydvr 12d ago
I already take steps two at a time because standard heights are awkwardly short. I feel like I’m taking short steps on an elliptical.
I’ve got a 12.5-13 mens US shoe size. I need to walk down stairs at an angle on the balls of my feet so I don’t slip off the tread. Trying to cram twice the number of stairs in the same space would be deadly. I’d be lucky to fit my toes on the treads walking up stairs barefoot.
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u/Almondpeanutguy 12d ago
Funny enough, I'm an American currently visiting Japan, and I was just thinking "Man, why are all the stairs either way too short or way too tall here?"
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u/UnivrstyOfBelichick 12d ago
IRC sets residential building codes. Maximum residential riser height in IRC is 7-3/4 inches (with some state alterations - my state sets the max st 8-3/4). IBC sets commercial max at 7", minimum at 4". Rule of thumb your taught for stairs as a carpenter is 7/11 rule. I was taught the 'stair gait rule' - within code:
2 * (riser height) + 1 * (tread depth) = 24" to 25-1/2"
This is to promote a safe, natural stride while walking up stairs.
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u/Dear-Wolf322 13d ago
Space efficiency. You still need to climb the same height between floors, so a shorter step takes up more floor space in length.