Rise and run of normal indoor stairs

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swimmer_spe

Well-Known Member
I am in the beginning of planning stages for an addition. We are either going up or out. To go up means putting in stairs. I am trying to figure out where those stairs will go in the main floor. What is a typical rise and run for an indoor step?

Steve123

Well-Known Member
About 7" rise and 11" run.
But there is a lot of very specific code requirements for stairways and no flexibility from your building inspector.
Google 'residential stairway code" and you will get countless hits.

Guzzle

Well-Known Member
r = rise, R = run
& r+R = 17.75”
& 2r + R = 25.

IBC says rise max = 7” & run max = 11” and
OSHA says r max = 9.5” & R min = 9.5”

Sparky617

Member
r = rise, R = run
& r+R = 17.75”
& 2r + R = 25.

IBC says rise max = 7” & run max = 11” and
OSHA says r max = 9.5” & R min = 9.5”
Homes aren't covered by OSHA, so best to follow IBC, but local codes office. Toughest part about cutting stringers is they can't have more than 3/16" variation from step to step. It becomes a tripping hazard. I might be off on the 3/16 but it is close to that, I doubt it is a 1/4" (4/16).

Guzzle

Well-Known Member
OK, IBC.

What is the difference in vertical inches between the higher floor & the lower floor?
What is the difference in horizontal inches between the rise of the lower step & the rise of the upper step?

BTW, these folding attic stair assemblies may violate these rise/run rules.

bud16415

Fixer Upper
Staff member
Moderator
The general rule I was taught was rise+run = 18"

Doing this will produce a comfortable step from a ladder to a gradual slope.

7_8" is the normal range so what I do is take the total height needing to be climbed and divide it by some numbers of steps until I get a number between 7-8" or how steep I want the climb to be. Then I subtract that number from 18" to see what a good run will be and multiply that by the number of steps I figured out in the first calculation. That will be the total length of the opening for the staircase to fit in.

In general a 8" step is an average climb and 7" an easy climb and 9" a tougher climb. Many times stairs to seldom used areas like an unfinished basement may be steeper in the 9" range.

bud16415

Fixer Upper
Staff member
Moderator
Also keep in mind the length of tread does not have to be the same as the run and you need proper foot placement and the nose of the tread will overhang the tread below it. There is a limit where a step becomes to steep to go down facing away from the step. Think of how we go down a ladder facing the ladder. 7"-8"-9" do not have this problem.

Sparky617

Member
OK, IBC.

What is the difference in vertical inches between the higher floor & the lower floor?
What is the difference in horizontal inches between the rise of the lower step & the rise of the upper step?

BTW, these folding attic stair assemblies may violate these rise/run rules.
I suspect the attic stair assemblies are considered more a ladder than a stairs. They are intended for occasional use not daily.

Guzzle

Well-Known Member
Many times stairs to seldom used areas like an unfinished basement may be steeper in the 9" range.
So they are trading off likelihood of injury with frequency of use.

Dangerous steps x used often = bad outcome
Dangerous steps x used seldom = not too bad
Safe steps x used often = OK
Safe steps x used seldom = very good
Makes sense.

We have old cars with low miles per year so we're exempt from emissions check. Same [public policy] principle.

Yeah, ladders may slip out, so more rules.
I've seen contractors using ladders @ a 45 degree angle. No me gusta.

bud16415

Fixer Upper
Staff member
Moderator
So they are trading off likelihood of injury with frequency of use.

Dangerous steps x used often = bad outcome
Dangerous steps x used seldom = not too bad
Safe steps x used often = OK
Safe steps x used seldom = very good
Makes sense.

We have old cars with low miles per year so we're exempt from emissions check. Same [public policy] principle.

Yeah, ladders may slip out, so more rules.
I've seen contractors using ladders @ a 45 degree angle. No me gusta.
I never said a 9” rise was dangerous. It is on the other hand more fatiguing than a 7” step that is more luxury. If you look at steps on courthouses and such where they have many steps they are often 6”x12” this makes for a very easy climb.

Often in old homes they have the main grand staircase and it is an easy rise and then there are back stairs (servant stairs) with a steeper rise.

Stair cases take room from both floors so in the case of a small home the basement staircase take room away from the first floor and a reason if they are not much used to make them closer to 9” rise to save space.

Guzzle

Well-Known Member
I have used the word "dangerous" loosely.

And my wife broke her ankle on a museum staircase because she couldn't see the step edge clearly. Neither could I.
So in my rush to get home, the cops pulled us over. Double whammy on that day.

bud16415

Fixer Upper
Staff member
Moderator
Stair spacing is very important. My dad made stairs from our garage into the basement when I was a kid. He messed up and the last/bottom step was just 4” instead of 8”. We all got used to it and it wasn’t an issue but my cousin came over and was expecting ether he was down or expecting another 8” step and he broke his ankle on the last step.

When in Mexico for work we had a new modern plant built and walking upstairs to the offices the stairs seemed off. Nice modern looking cast steps is what they looked like. Finally I pulled out my tape measure and found no two steps had the same rise. They were as much as an inch off. When I asked about it I was told you are in Mexico they don’t measure they go by eye. I said are these the same people building our products?

bud16415

Fixer Upper
Staff member
Moderator
Speaking of steps. Why in the year 2022 do we have the President of the USA walking up and down mobile stairs to get into the fanciest airplane in the world.

I would be willing to design them a mobile elevator and it could be covered in bulletproof glass and take up half the space of that stair thing.

Guzzle

Well-Known Member
Speaking of steps. Why in the year 2022 do we have the President of the USA walking up and down mobile stairs to get into the fanciest airplane in the world.

I would be willing to design them a mobile elevator and it could be covered in bulletproof glass and take up half the space of that stair thing.
I'll pass that on to Mr. B!
My GP says he's seen signs of Alzeimers in said pres.

Guzzle

Well-Known Member
fatiguing
???
Never heard of it!

Climbing 8' in 8 seconds takes 1/4 hp.
Climbing 6 flights in 20 seconds takes 1 hp. Did this once, maybe still can. Saw a guy at the gym put out 2 hp for a few seconds.
A world class cyclist can do 1/2 hp for 20 minutes.
For 8 hrs, maybe a worker can put out 1/12 hp, average.

Try it.
Find several flights of steps, weigh yourself, measure the height, run like hell & time yourself.
Don't scare bystanders on the staircase.
Don't end up on the evening news.

Eddie_T

Well-Known Member
I suspect swimmer has left the building.

Guzzle

Well-Known Member
I suspect swimmer has left the building.
To climb stairs in a big hurry & thereby test his physical limits?

Eddie_T

Well-Known Member
From off topic boredom?

swimmer_spe

Well-Known Member
I suspect swimmer has left the building.
No, I just got the information and just scroll past the trolls.