# Tread/Riser Dimension Amendments



## NH09 (Jan 13, 2011)

I was wondering if there was anyone out there whose state (or municipalities) have amended the tread/riser requirements of the IRC. There is currently an organization here in New Hampshire who would like to change these requirements from 10" min. run/7 3/4" max. rise to 9" min. run/8 1/4" max. rise. Also, does anyone out there know why the old BOCA codes allowed the 9"/8 1/4" up until the early 90's and then changed to 10"/7 3/4"?


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## raider1 (Jan 13, 2011)

Yes, Utah has amended the rise/ run requirements of treads to be a maximum 8" rise and minimum 9" run provided that there is a nosing on the treads of not less than 3/4" and not more than 1 1/4". For treads that don't have a nosing the minimum run is 10". This is a State amendment for the IRC.

Chris


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## jar546 (Jan 13, 2011)

PA=  8-1/4" rise, 9" run


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## High Desert (Jan 13, 2011)

Oregon 8 inch rise, 9 inch run.


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## TimNY (Jan 13, 2011)

NY 8-1/4" rise 9" run

I would add that I routinely see these dimensions maxxed out and the stairs seem perfectly comfortable to me..


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## Yankee (Jan 13, 2011)

Would those who answered in the affirmative give the reason(s)? And also, what else has the State amended (from the IRC)?


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## righter101 (Jan 13, 2011)

Reason for rise-run

It has been explained to me that the change in the rise/run was based on some sort of safety committee or organization that studied stairway related accidents, etc...

and their conclusions were that reducing the max rise and increasing the min tread would substantially lower the incidents of injury.

This is only something that has been passed on to me by older code officials, much more experienced and wiser than I.

Sounded believable.

I think that 8" risers are just fine, but in Washington, we have not amended it.


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## righter101 (Jan 13, 2011)

Washington State has not amended the tread rise/run, but they have amended a number of other sections.

Go to https://fortress.wa.gov/ga/apps/sbcc/page.aspx?nid=4

and scroll down to the very bottom and you can view or download the State Amendments to all of the codes.  They have them in a format that is printable and says "insert facing page xxx", so we print them out in orange paper and stick them in our code books where they belong.

FYI


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## PORTEOUS (Jan 13, 2011)

Same here in MT, 9"run, 81/4 rise.


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## brudgers (Jan 13, 2011)

The reasons for the change are that lower risers and longer treads are safer.

To put it in perspective, a person is about 15 times more likely to die from falling than in a dwelling fire...even if requiring fire sprinklers gives the ICC a woody.


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## Architect1281 (Jan 14, 2011)

Hello NH RI has had this in one form or another since 1977 statewide codes BOCA/CABO

started to permit the 24 foot deep house most residents have survived just fine

R311.5.3.1 Delete IRC R311.5.3.1 and R311.5.3.2 and substitute the following:

311.5.3.1 Riser height. The maximum riser height shall be 8-1/4 inches (210 mm). The riser shall be measured vertically between leading edges of the adjacent treads. The greatest riser height within any flight of stairs shall not exceed the smallest by more than 3/8 inch

(9.5 mm).

311.5.3.2 Tread depth. The minimum tread depth shall be 9 inches (229 mm). The tread depth shall be measured horizontally between the vertical planes of the foremost projection of adjacent treads and at a right angle to the tread’s leading edge. The greatest tread depthwithin any flight of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm). Winder treads shall have a minimum tread depth of 9 inches (229 mm) measured as above at a point 12 inches (305) mm from the side where the treads are narrower. Winder treads shall have a minimum tread depth of 6 inches (152 mm) at any point. Within any flight of stairs, the greatest winder tread depth at the 12 inches (305 mm) walk line shall not exceed the smallest by more than 3/8 inch (9.5 mm).

311.5.3.3 Profile. The radius of curvature at the leading edge of the tread shall be no greater than 9/16 inch (14.3 mm). A nosing not less than ¾ inch (19.1 mm) but not more than 1-1/4 inches (32 mm) shall be provided on stairways with solid risers. The greatest nosing projection shall not exceed the smallest nosing projection by more than 3/8 inch (9.5mm) between two stories, including the nosing at the level of floors and landings. Beveling of nosing shall not exceed ½ inch (12.7 mm). Risers shall be vertical or sloped from the underside of the leading edge of the tread above at an angle not more than 30 degrees from the vertical. Open risers are permitted.

Exception: A nosing is not required where the tread depth is a minimum of 11 inches (279 mm).


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## jar546 (Jan 14, 2011)

Forgot to mention that our amendment only applies to residential in PA


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## Jobsaver (Jan 14, 2011)

Doesn't making this revision constitute a reduction in code requirements, the primary purpose of which is to fit a stair into a smaller footprint?


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## jar546 (Jan 14, 2011)

In PA as the UCC was being rolled out, the modular home industry lobbied for this change.  One of many concessions for small interest groups.


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## Yankee (Jan 14, 2011)

So instead of lobbying the ICC, the special interest group(s) figure they can pick off States one at a time because they have more political leverage on the state level.


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## NH09 (Jan 14, 2011)

I had a chance to read the proposal, and it looks like there are actually three groups proposing the change; the modular manufacturers being one of them. I find the 10"/7 3/4" stairways easier to use, but otherwise have no opinion on the matter. I will try to find some data reinforcing the case either way and post anything interesting - thanks for all your replies.


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## rogerpa (Jan 14, 2011)

Michigan 8-1/4" x 9". Rule 519.  Sections R311.5.3.1 and R 311.5.3.2 of the code are  amended  to read as follows:R311.5.3.1.  Riser height.  The maximum riser height shall be  8  1/4  inches (210 mm).  The riser shall be measured vertically between  leading  edges  of the adjacent treads.  The greatest riser height within any flight  of  stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm)  R311.5.3.2.  Tread depth.  The minimum tread depth shall be 9  inches  (229 mm).  The tread depth shall be measured  horizontally  between  the  vertical planes of the foremost projection of adjacent treads and at a right angle  to the tread's leading edge.  The greatest tread  depth  within  any  flight  of stairs shall not exceed the smallest by more than 3/8 inch (9.5 mm).   Winder treads shall have a minimum tread depth of 10 inches  (254  mm)  measured  as above at a point 12 inches (305 mm)  from  the  side  where  the  treads  are narrower.  Winder treads shall have a minimum tread depth of  6  inches  (152 mm) at any point.  Within any flight of stairs,  the  greatest  winder  tread depth at the 12-inch (305 mm) walk line shall not exceed the smallest by more than 3/8 inch (9.5 mm).All Michigan amendments Jake Pauls advocated for 7" x 11" geometry for years at ICC. The 7-3/4" x 10" was a compromise. Jake often sited studies of various geometries that did not include the 8-1/4" x 9" geometry.According to the NEISS, more injuries occur on floors and floors w/rugs than on stairs. The incident reports for stair injuries contain statements like: "I didn't turn on the light because I didn't want to wake anyone and fell down the basement stairs after mistaking the basement door for the bathroom door", or "I hit my head on the ceiling and lost my balance", or the ten year old who "jumped the last 4 risers and turned his ankle when he hit the floor. In the interest of full disclosure, this was also reported as a floor injury.

View attachment 342


Stair injuries.pdf

Stair injuries.pdf


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## Yankee (Jan 14, 2011)

Many of the numbers used in the code are picked as a compromising number and don't necessarily have any tested technical background.

That's the point, a number needs to be used and if jurisdictions want to start changing the compromising numbers in the adopted code to suit someone's benefit, that leaves every number in the code open for amendment.

Why go down that road?

I see that the states that have adopted a different set of stair numbers also have long lists of adopted amendments. . . . a slippery slope.

Having said that, the tread width is more important as a safety item than the rise, and it is the overall run of the stairs that they are trying to reduce.


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## Jobsaver (Jan 14, 2011)

Yankee said:
			
		

> I see that the states that have adopted a different set of stair numbers also have long lists of adopted amendments. . . . a slippery slope.


I'm undecided. The slippery slope may be when the regional codes were abolished, and the ICC formed.

With stairs, it is tread width in relation to the rise that is the most important.


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## mtlogcabin (Jan 14, 2011)

PORTEOUS said:
			
		

> Same here in MT, 9"run, 81/4 rise.


It is the old CABO numbers that our state decided to stay with. I don't like them for a number of reasons but it is what it is.


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## rogerpa (Jan 14, 2011)

Yankee said:
			
		

> Having said that, the tread width is more important as a safety item than the rise, and it is the overall run of the stairs that they are trying to reduce.


I think that consistency of the dimension is most important, especially the rise. Many times I've tripped while ascending stairs that have a "long riser" inserted in mid-flight.  Also the relationship (ratio) between the run and rise so that the user is not required to "stutter step" to maintain a rhythm.


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## High Desert (Jan 14, 2011)

http://www.accuratebuilding.com/services/legal/papers/stair_ramp_safety.html

*An excerpt from the article on Stair & Ramp Safety that I found interesting.*

The problem is that most stair incidents usually happen one at a time and are not considered newsworthy. And when a major stair or ramp incident does occur, it is hidden by the event that triggered the catastrophe.

For example, in 1903, in the Iroquois Theatre in Chicago, 500 people died. They were found piled 8 feet deep, crushed in a stampede that started because of a fire that didn't even burn down the theatre. The real reason for the deaths was that the stairs and exit ramps were designed incorrectly. But what got the headlines? The culprit was the stairs, but the papers said “FIRE!”

Again, in 1942 at The Coconut Grove in Boston, 700 people attempting to escape a fire died because of poor stair and exit design. The headlines should've read “Stairs and Exits Kill 700”, but again, they didn't.


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## Paul Sweet (Jan 14, 2011)

Virginia has also amended the IRC to stay with the old CABO dimensions - 8-1/4" risers & 9" treads.


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## Yankee (Jan 14, 2011)

I agree that consistency in the dimensions is the most important aspect. After that though, a riser height of 7 1/2 or 8 1/4 works equally well for me. But a thread depth of 9" (plus nosing) is too small especially going down. And, have you noticed that average shoe size has changed dramatically in the last two generations to be larger? T

But my point is, if the number is so drastically off for whatever reason, the change would be better to happen at the ICode level. Otherwise the special interest "amendment" door has opened a little more.


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## brudgers (Jan 14, 2011)

Yankee said:
			
		

> So instead of lobbying the ICC, the special interest group(s) figure they can pick off States one at a time because they have more political leverage on the state level.


There's a bit more to it than that. Changes in stair dimensions have a huge effect on the homebuilding industry in a way that most other code changes do not because changes to the stair requirements radically affect floor plans, particularly as houses get smaller and space becomes more critical...I lived through proposed stair changes during the FBC 2004 cycle while at Pulte during the boom...the FBC was going to follow NFPA 101 with 7/11 for dwellings, until order was restored by the legislature in the waining days of the session and NFPA 101 Florida edition was modified to match the building code.


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## NH09 (Jan 14, 2011)

I was sent a link to a report "A Review of the Literature and Data Concerning Stair Geometry and Other Characteristics". I've only begun to read the document, but it appears there is a lot of information in it. Thanks for the other link High Desert, I'll take a look at that one as well. Here's a link the the review if anyone is interested:

http://www.toolbase.org/Best-Practices/Codes-Regulations-Standards/stair-safety


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## Yankee (Jan 14, 2011)

brudgers said:
			
		

> There's a bit more to it than that. Changes in stair dimensions have a huge effect on the homebuilding industry in a way that most other code changes do not because changes to the stair requirements radically affect floor plans, particularly as houses get smaller and space becomes more critical...I lived through proposed stair changes during the FBC 2004 cycle while at Pulte during the boom...the FBC was going to follow NFPA 101 with 7/11 for dwellings, until order was restored by the legislature in the waining days of the session and NFPA 101 Florida edition was modified to match the building code.


I am well aware of the impact of the stair design on the floor plans and the argument that the proposed numbers would aid the building industry to build less expensive houses. But the line should be somewhere and if the line in the IRC isn't a good enough compromise, then that is where the change should take place not on a state by state basis. This code item is not intertwined with regional climates etc etc where an amendment might be warranted. Unless for some reason 90% of the population of a state has smaller than average feet . . . uhhh, , let's not go there . . .


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## georgia plans exam (Jan 14, 2011)

Georgia amendments to R311 kept the 7 3/4" riser height but allows a 3/4" variation at the first and last riser and allows a 9" tread depth.

GPE


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## tbz (Jan 14, 2011)

The 8-1/4" by 9" tread is amended in more places than not, as for the 7-3/4" x 10" it was a compromise from just adopting the 7" x 11" from what I can remember.  However, I could be wrong.

The main key though is no change in the geometry, the 3/4" change allowed in the GA adoption I would say is a bigger problem then the 8-1/4" vrs the 7-3/4".

We all have come down those set of stairs that has a small riser at the bottom and almost trip in gait.

The same is true when the top riser is higher than the flights standard you tend not to pick the foot up enough and trip.

NJ amended it in the IRC to 8-1/4" x 9" when adopted.


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## TimNY (Jan 14, 2011)

Well, the analyzing seems to be focusing on who is driving the change in the states.. I am curious as to who determined the requirements in the unabridged code?  I just don't see an issue with the 8-1/4"x9".. I have that in my own house.

Interesting story one of our NYS code instructors told us about our building code prior to using the i-codes.. "you know why the ceiling height was 7'-6"?  Well, I asked one of the guys who wrote the code.. he said they were all in the office one day and had to decide on a ceiling height.  One guy said 7'-6" sounds good"


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## brudgers (Jan 14, 2011)

Yankee said:
			
		

> I am well aware of the impact of the stair design on the floor plans and the argument that the proposed numbers would aid the building industry to build less expensive houses. But the line should be somewhere and if the line in the IRC isn't a good enough compromise, then that is where the change should take place not on a state by state basis. This code item is not intertwined with regional climates etc etc where an amendment might be warranted. Unless for some reason 90% of the population of a state has smaller than average feet . . . uhhh, , let's not go there . . .


Local governments should make local decisions and state governments should make state decisions. We don't need a national building code, and in any event the dictates of the ICC should not take precedence over state governments. Supreme executive authority derives from a mandate from the people not some farcical aquatic ceremony.


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## peach (Jan 15, 2011)

almost every jurisdiction amends it; the IRC requirement adds a requirement of about 56 extra square feet per floor (it doesn't work in narrower, shallower houses).

MHO: people who live in a house are going to be familiar with the stairs; it's the turnout gear that fire fighters wear that make the steeper stairs harder to manipulate.

In Single family  homes, the fire fighters generally aren't going to have to deal with more than 3 flights of stairs (or the house is probably an IBC building).


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## peach (Jan 15, 2011)

almost every jurisdiction amends it; the IRC requirement adds a requirement of about 56 extra square feet per floor (it doesn't work in narrower, shallower houses).

MHO: people who live in a house are going to be familiar with the stairs; it's the turnout gear that fire fighters wear that make the steeper stairs harder to manipulate.

In Single family  homes, the fire fighters generally aren't going to have to deal with more than 3 flights of stairs (or the house is probably an IBC building).


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## brudgers (Jan 15, 2011)

peach said:
			
		

> MHO: people who live in a house are going to be familiar with the stairs; it's the turnout gear that fire fighters wear that make the steeper stairs harder to manipulate.


I doubt residential stair present a challenge, given EE&RO requirements.


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## Yankee (Jan 15, 2011)

brudgers said:
			
		

> Local governments should make local decisions and state governments should make state decisions. We don't need a national building code, and in any event the dictates of the ICC should not take precedence over state governments. Supreme executive authority derives from a mandate from the people not some farcical aquatic ceremony.


I think NH09's question was should his state amend the code, , , the decision NOT to amend the ICC code is then still A State Decision and is still a mandate from the people of that State. As for me, if there isn't some driving local reason to change something in the adopted ICC code, then it should not be changed. If a state wants to write their own code book then that is what they should do.


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## Yankee (Jan 15, 2011)

peach said:
			
		

> almost every jurisdiction amends it; the IRC requirement adds a requirement of about 56 extra square feet per floor (it doesn't work in narrower, shallower houses).


I don't believe that number is correct. Assuming 99" fl to fl, the 10/7.75 is a 10' run and the 9/8.25 is a 8'3" run. that is 1'-9" longer time 3' for the width, that is less than 6sf. , , ah, you must have had a typo and hit the "5" also.Alrighty then, I will compromise and say that IF the house is going to be 24' wide, then they are allowed the 9/8.25. But if they "want" a wider house or a house with taller ceilings, they must meet the 10/7.75.

That's fair, right?


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## TimNY (Jan 15, 2011)

I never went into a burning residence and said, "man, these stairs suck".  "It's F$&*$& HOT IN HERE!" maybe.. but I wouldn't even bring the fire service into this discussion on a residence.. I just don't think there is anything to back it up.

Do enough studies and you can bend the data any way you want.  In reality I never heard a peep about the tread depth when a building was on fire.

How about the ICC take a hint from the people adopting their codes and just change it.


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## Architect1281 (Jan 15, 2011)

Job Saver - Not so Slippery in RI -

in order to keep the stairs from being slippery provide the following ammendment to the IRC 2009

R313.1 Delete R313.1 and 313.2 and substitute the following

R 313.1 General.

Automatic fire sprinkler if installed at the applicants option will be in conformance with Appendix R


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## Daddy-0- (Jan 15, 2011)

As Paul S. said, we (Virginia) amended the stair section. Virginia changes a lot of the codes through an amendment and appeals process and then the ICC actually publishes a "Virginia" code which is the IRC, IBC, IPC etc. with the Virginia changes in it.

We have a lot of colonial style houses here which are typically not very deep. The stairs in those houses often do not hit a landing and turn. The amended stair rise/run helps fit this style of stairs into the most popular Virginia house designs.


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## Yankee (Jan 16, 2011)

I understand the design issue. I wonder though, how many new houses, even lower end houses, are less than 28' wide based on other wants? Since I don't have many if any in my area, I'd like to know what the other experiences are? In _general_, a "style" can be maintained with a small change in "scale" (ie from 24' to 28'), if a design pro is involved even to a small extent.


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## TimNY (Jan 16, 2011)

Has there actually been data to support a 10" tread is safer than a 9" tread, or is it just a matter of "it's bigger, so it HAS to be better"

If we eliminated stairs altogether and just used a series of landings, I bet it would be even safer yet!

I just don't see the need.  I am speaking in regard to the residential code; in the commercial code I can understand it based on increased occupancy, unfamiliarity with the stairs etc.


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## Yankee (Jan 16, 2011)

TimNY said:
			
		

> How about the ICC take a hint from the people adopting their codes and just change it.


Doesn't someone not on ICC staff need to bring it forth?It's a number chosen as a compromise between two other numbers. There's a reason we don't allow ladders but I doubt there is an exact number that is "safer" than another similar number.

It sounds like most on this board would be in favor of changing the number based on . . . . not sure what, but there you have it.


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