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!
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.
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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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.
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.
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.
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.
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.
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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.
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.
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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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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