Tread/Riser Dimension Amendments

[NH09]

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"?

 

[raider1]

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

 

[jar546]

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

 

[High Desert]

Oregon 8 inch rise, 9 inch run.

 

[TimNY]

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..

 

[Yankee]

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

 

[righter101]

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.

 

[righter101]

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

 

[PORTEOUS]

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

 

[brudgers]

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.

 

[Architect1281]

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).

 

[jar546]

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

 

[Jobsaver]

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?

 

[jar546]

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.

 

[Yankee]

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.

 

[NH09]

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.

 

[rogerpa]

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

 

[Yankee]

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.

 

[Jobsaver]

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.

 

[mtlogcabin]

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.

 

[rogerpa]

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.

 

[High Desert]

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.

 

[Paul Sweet]

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

 

[Yankee]

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.