Residential Stair And Handrail Code (2020 IRC Guide)

Are you interested in learning the latest IRC stair code for residential homes?

Stairs are an important way to exit a home level and to escape a hazard --- such as a fire.

In this guide, I will go over...

  • the basics of stairway code such as treads, risers, and guardrails
  • common safety issues with stairs
  • what home inspectors look for

Let's get started with this guide!

residential stair code

What Is The Residential Stair Code?

The residential stair code is a sub-section in the Means of Egress section of the International Residential Code handbook in Chapter 3 entitled Building Planning.

The International Residential Code (Source)

Chapter 3: Building Planning >> Section 311: Means of Egress >> Sub-Section 311.7: Stairways

Technically, stairs is considered a 'means of egress' which basically means a way to escape from a home (or level of a home). The IRC is updated every 3 years, and the last update was in 2018.

This guide isn't meant to be exhaustive of every single code in the IRC, but it is meant to present the basics and what I think is the most important. There are numerous exceptions to the IRC stair code, and for an authority source I recommend checking out the IRC website.

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Stairway Width

The stairway width above the handrail and below the minimum headroom height shouldn't be less than 36 inches.

Below the handrail, the width should be at least 31.5 inches if there is one guardrail.

If there are guardrails on both sides, then the minimum width should be 27-inches below the guardrail top height.

stairway width residential stair code (1)

Headroom

Headroom is the space required from the stairs to the top. Basically, this rule helps prevent people banging their head on ceilings.

I recently did a home inspection on an old home with numerous additions. The stairs to the basement had a ceiling protrusion that was probably around 5 feet and I repeatedly hit my head on the top. Ouch.

The minimum headroom as measured from the stairs to the top should be at minimum 6-ft and 8-in.

minimum headroom residential stair code

Risers

Riser height should have a minimum height of 7-3/4 inch height. There shouldn't be a height difference of more than 3/8" between the tallest and shortest riser.

Open Risers

If the stairs has open risers, then anywhere above 30" from floor should not permit a sphere of 4-inch diameter to pass through. Basically, if there are no risers, then a child's head shouldn't be able to pass through above than 30" point from ground.

Treads

The treads (horizontal portions) of a stairs should be at minimum 10-inches. The longest tread versus the shortest tread shouldn't be more than 3/8-inch.

That basically sums of the basics of the stairs rise and run code.

riser and tread length residential stair code

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Handrails

The stair railing height code in the IRC states that the minimum height is 34-inches and the maximum height is 38-inches. The top of the handrail is measured from the stair nosing, as if you drew a diagonal line across the top of the stairs.

handrail residential stair code 2
handrail residential stair code

What Do You Look For As A Home Inspector?

During my home inspections, the most common areas that I cite in regards to stairs come down to a few items.

1. Four Inch Sphere

Anywhere above 30-inches from the ground, there needs to be a guardrail to prevent a hazardous fall for an adult or child. In the home inspection world (and the IRC), there is a rule known as the four inch sphere rule.

Basically, it means that a 4-inch sphere should not be able to pass through the handrail. The 4-inch sphere is equivalent to the head size of a small child. If the child's head can get through, then their whole body can get through.

stair rail code safety four inch sphere rule

2. Loose Railing

Many times when I push on a railing, it is very loose. Most indoor stair handrails have a little give, but if it is obviously loose, I will call it out. For decks or hallways, the guardrail is more significant since numerous people may be leaning on the railing such as at a party.

3. Missing Railing

It never ceases to amaze me that a stairway can have a missing handrail, but it happens. Remember, any time you can fall more than 30" inches, there should be a guardrail.

4. Missing Lighting

Stairs should always have illumination for obvious reasons. If you are always going up and down stairs without lights, sooner or lighter you are going to take a fall. Stairs with more than six risers should always have a light switch at the top and bottom --- a three way switch.

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Conclusion

There you have it, the basics of the IRC stair code. And again, the IRC is updated every three years, but usually the basic code remains the same. This guide isn't meant to present every single stair code --- there are NUMEROUS exceptions stated in the actual IRC stairway section. 

To really get the final word on any residential code, you should always go to the actual source such as the IRC website.

However, don't forget that state, county, or city codes may supersede the IRC.

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4 thoughts on “Residential Stair And Handrail Code (2020 IRC Guide)”

  1. What is the code for the placement of the Newell post(s) At the top of the stairs, relative to the floor level stair nosing?

    Reply
    • Hey Noah,

      The IRC only mentions newel posts in one small area, “R311.7.8.4 Continuity” and describes that the railing has to terminate in either a newel post, returned to the wall, or a safety terminal — basically to prevent peoples clothing from getting caught on railing in case of fire/emergency.

      It never mentions nosing, only the riser.

      It states that the end of the railing (newel post) at minimum needs to terminate “directly above the top riser”.

      My homes top newel post actually overlaps the edge of nosing and the riser line. If at least part of the newel post is directly above the riser line, I think you are good to go.

      Good luck!

      Reply
  2. I am installing a 2 round railing for my outside steps . If I dont hit a stud will the partical board be strong enought to support the railing and the people using it?

    Reply
    • Hi Ardell,

      I don’t think such an installation would be to code. In section R301.5, its says that a “concentrated load applied in any direction at any point along the top” of 200 pounds per square foot for guards & handrails. I wouldn’t settle for an OSB wall connection.

      Good luck!

      Reply

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Arie Van Tuijl

Arie Van Tuijl

Arie is the founder of Home Inspector Secrets, an online resource dedicated to helping people understand how homes work. He is a licensed home inspector in two U.S states and owns a residential and commercial inspection company. To ask Arie a question, please use the comment box at the bottom of the relevant article.

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