Stairs, they are everywhere, yet for so many they never give it much of thought…till.

We all seem to have this little built in stair-o-meter when we climb or descend a flight of stairs. We seem to be able to feel, very quickly,  if the stairs are not built correctly or more correctly uniformly. I think most have almost fallen or stumbled when going down a set of stairs and the bottom stair is short and makes us want to stumble or trip. Uniformity in stairs is essential for safe stairs.

Stairs have many rules due to their function which makes them more inherently dangerous.  An estimated 24,760,843 patients were treated in emergency departments for a stair-related injury during the 23-year study period (1990 – 2012), averaging 1,076,558 patients annually, or 37.8 injuries per 10,000 United States residents. There are around 12,000 fatalities yearly from stair related falls.

Stairs can become a dangerous part of our daily life especially for the elderly or disabled.

Let’s start off with the current standard for stairs. I am going to be focusing just on the rise and run of the stairs.

From the 2015 IRC– which Washington State is currently under. 
(This is the current model code, the 2018 IRC has which was to be implemented in 2020 in now due to be implemented in Feb.1 2021 because of Covid-19)

R311.7.5 Stair Treads and Risers

Stair treads and risers shall meet the requirements of this section. For the purposes of this section, dimensions and dimensioned surfaces shall be exclusive of carpets, rugs or runners.

R311.7.5.1 Risers

The riser height shall be not more than 7 – 3/4 inches (196 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). Risers shall be vertical or sloped from the underside of the nosing of the tread above at an angle not more than 30 degrees (0.51 rad) from the vertical. Open risers are permitted provided that the openings located more than 30 inches (762 mm), as measured vertically, to the floor or grade below do not permit the passage of a 4-inch-diameter (102 mm) sphere.

Exceptions:

The opening between adjacent treads is not limited on spiral stairways.

The riser height of spiral stairways shall be in accordance with Section R311.7.10.1.

R311.7.5.2 Treads

The tread depth shall be not less than 10 inches (254 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).

R311.7.5.3 Nosings

The radius of curvature at the nosing shall be not greater than 9/16 inch (14 mm). A nosing projection not less than 3/4 inch (19 mm) and 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 (9.5 mm) between two stories, including the nosing at the level of floors and landings. Beveling of nosings shall not exceed 1/2 inch (12.7 mm).

Exception: A nosing projection is not required where the tread depth is not less than 11 inches (279 mm).

2015 IRC Basic Stairs Guide

https://wenatcheehomeinspection.com/wp-content/uploads/2020/11/2015-Tip-Sheet-1-Basic-Stairs.pdf

So this is where we stand currently. This has been close to the same standard since the adoption of the IRC Model codes

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Below is a Chart on some of the different rule from previous building codes that show that there was some differences than the current rules.

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We will now travel back a little in time to see where we came from to  get to where we are today.

From the BBC 10 dangerous things in Victorian/Edwardian homes- (So this dates from around the 1830’s.)

“Killer staircases – As houses were thrown up rapidly, one area of design that was often overlooked was the staircase, especially those installed for the use of servants. Made too narrow and too steep, with irregular steps, the servants’ staircase was a deadly construction. Add the weight of carrying trays or the complication of long skirts, and the stairs could easily prove fatal.”

https://www.bbc.com/news/uk-25259505

Out of this came a formal breakthrough in design.

A treatise on the construction of staircases and handrails was published in 1820  by Peter Nicholson (1765-1844). A fantastic bit of work in architecture.


From “A treatise on the construction of staircases and handrails” – published in 1820

“The general rule may therefore be as follows: supposing any step to be taken as a standard to find the height of another step whose breadth is given,

Multiply the breadth and height of the given step, and divide the product by the breadth of the required step, and the quotient will be the answer; or as the breadth of the required step is to the breadth of the given step, so is the height of the given step to the height of the required step.

Thus, taking as a standard, a step twelve inches in breadth and five and a half in height, we may easily find the height of another whose breadth is given ; thus, supposing the breadth be ten inches, to find the corresponding height we have 10 : 5 -½  : : 12 (12 x 5-½ /10) = 66/10 = 3/10; which is about the height that common practice allows.

The proportions of the steps being thus regulated, the next consideration is the number which the height of the stair will require.

The rule is, the height of the story or distance from floor to floor being given in feet and inches, reduce the whole to inches, and divide this number of inches by the height of a step, and we shall have the number required.

It is desirable to have rules for regulating the proportions of steps; yet architects

and workmen need not be tied down to them, but may vary as circumstances require.

When the height of the story is very considerable, resting-places become necessary.

In very high stories, that admit of sufficient head room, where the staircase is confined with respect to the plan, the stair may have two revolutions; that is, the passenger may go twice round the newel or well-hole in ascending or descending; and this becomes necessary, otherwise the steps will be enormously high.”

As you can see from this little information we are now getting very close to the modern rules for stairs.

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Then there is the FORMULA –  “g+2r”.      G stands for “Going” which in modern terms means run.

This  g+2r equation goes back to the 17th century French architect Francois Blondel. This may be disputed but it does show that these stride and safety factors were well known for quite some time.


The formula 2 times riser + tread equals 24.6 inches (625 mm), the length of a stride. Thus a 7 inches (178 mm) rise and a 10.6 inches (269 mm) tread exactly meets this code. If only a 2 inches (51 mm) rise is used then a 20.6 inches (523 mm) tread is required. This is based on the principle that a low rise is more like walking up a gentle incline and so the natural swing of the leg will be longer.

From this information we can see for a few 100 years we understood that there should be applied rules for stairs and taking in the biomechanics of how we walk.

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In the video below you can see what happens when just a slight variance in the rise of a stair over a flight can present a tripping hazard. For many this may seem like a very minor thing till it is not. Many of elderly trip and fall on stairs daily which can lead to breaks and fractures or even worse a hip fracture. 

300,000 people fracture their hip yearly with around 90% of those who do fracture their hips are over 65 yo. The mortality rate for those elderly people with a hip fracture is around 21%.

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So the next time you evaluate your stairs take in the account of those who may be traversing them and what the potential for injury may be. For some improper stairs  can turn deadly.

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Stairs – A Toast

Here’s to the man who invented stairs

And taught our feet to soar!

He was the first who ever burst

Into a second floor.

The world would he downstairs to-day

Had he not found the key;

So let his name go down to fame,

Whatever it may be.

———————————————

Oliver Herford

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Here is some additional information

Killer staircase
https://www.youtube.com/watch?v=L1vqQi5Tl70

https://archive.org/details/treatiseonconstr00nich/page/2

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.204.6751&rep=rep1&type=pdf

https://www.youtube.com/watch?v=L1vqQi5Tl70

https://iitcoa1styear.files.wordpress.com/2017/10/koolhaas-rem_elements_stairs-excerpts.pdf
https://www.crystalrunhealthcare.com/articles/what-makes-hip-fractures-so-dangerous-elderly

http://www.equalfact.com/measure/length/tread-depth-of-stair

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If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service

Coordinator & Instructor- Fundamentals of Home Inspection-  Bellingham Technical College

Former WA Home Inspector Advisory Licensing Board

www.ncwhomeinspections.com                                                   509-670-9572

 You can follow me on Facebook, Twitter, Google+ and on my website Blog.

 

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If you find any errors or have additional information that would expand on any code, building standards or manufacturer requirements please let me know.

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…  

Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service

Coordinator & Instructor- Fundamentals of Home Inspection-  Bellingham Technical College

Former WA Home Inspector Advisory Licensing Board

www.ncwhomeinspections.com                                                   509-670-9572

 You can follow me on Facebook, Twitter, Google+ and on my website Blog.

 

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