The building code for stairs and railings can get a bit tedious, but it’s important to get it right. Stairs are an important way to exit a home and to escape hazards — such as a fire.
In this guide, I will go over…
- Stairway code basics such as treads, risers, and guardrails
- Common safety issues with stairs
- Things home inspectors look for
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 are considered a ‘means of egress’ which basically means a way to escape from a home (or level of a home). The IRC is a model code standard that has been adopted by many U.S. states and some Caribbean and Latin American countries.
The International Residential Code is updated every 3 years, and the last update was in 2018. This guide isn’t meant to go over every residential stair code detail in the IRC, but it is meant to present the basics and what I think is the most important.
Local Building Codes
Always remember that the staircase code of your state and county or city will almost always take precedence over the IRC unless the IRC has been totally adopted. Your state or county will likely have exceptions to the IRC standard as well.
IRC Staircase Code Exceptions
The International Residential Code standard has numerous exceptions to its residential stair code, and if any code in this articles doesn’t fit what you are trying to do, I recommend consulting the IRC and your local code.
The IRC has exceptions to its code in almost every section in its stair code chapter.
Minimum Stair Width
The minimum stair width above the handrail and below the ceilingshouldn’t be less than 36 inches.
Below the handrail, the minimum width should be at least 31.5 inches if there is one handrail.
If there arehandrails on both sides, then the minimum width of the rails should be at least 27-inches below the handrails.
Headroom is the space required from the stairs to the top. Basically, this rule helps prevent people banging their head on ceilings and being a safety hazard.
This rule will more likely be an issue on older homes that I inspect, and they are usually grandfathered into existing code due to their age. 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. It is measured from the imaginary diagonal slope atop the stair risers or nosings.
This rule also applies to landings as measured from any area on the landing to the ceiling.
Vertical rise is the total height of the stairs as measured between floors or landings.
The maximum vertical rise of stairs according to the IRC shall be 151″ or about 12.5-feet.
Riser height should have a maximum 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 stair tread code as well as risers.
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The stair nosing is the portion of the tread that sticks out beyond the riser. Stair nosings usually have a circular or beveled edge.
According to the IRC, the nosing shall have a minimum depth of 3/4″ and a maximum depth of 1-1/4″ depth.
Similar to the risers and treads, there shouldn’t be more than a 3/8″ difference between the length of the nosings.
Nosings are also not required if the stair treads are 11-inches or greater.
Landings are required at the top and bottom of stairs. One reason is that if there is a fall, you will only fall down the stairs a certain distance before hitting a landing.
Landings also make it easier to make turns onto a level or a different stair direction.
The width of the landing must not less than the width of the stairs.
Also, the horizontal slope of landings shouldn’t be more than a 2% slope gradience.
Handrails are very important to home inspectors, and I have called out numerous stairs that are missing or have defective handrails.
The IRC states that if there are four or more risers, then handrails are required.
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 Projection, Clearance, and Continuity
Handrails shall have a maximum projection from the wall of 4-1/2 inches. And there should be a minimum of 1-1/2 inches of clearance between the handrail and the wall.
The handrail also needs to be continuous from the top of the highest riser to the lowest riser.
The end of the handrail also needs to return to the wall, have newel posts, or safety terminals. Handrail termination is important so clothes or equipment doesn’t get stuck on the end of the handrail, especially in emergency situations.
Handrail Grip Size
The handrail should have a minimum 1-1/4″ diameter and a maximum 2″ diameter if it is circular in shape.
If the handrail is not circular, it should have a minimum 4″ perimeter (not diameter) and a maximum 6-1/4″ perimeter. If the handrail is not circular and has more than a 6-1/4″ perimeter, then graspable finger recesses should be provided on both sides of the rail.
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 just a few items.
My favorite book on code is by DeWalt called Residential Construction Codes.
Residential Construction Codes is the complete guide to the 2018 residential building codes. It is highly readable and has great illustrations. It also includes those weird code exceptions that even code enforcers screw up.
You can view the price of Residential Construction Codes on Amazon right here.
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.
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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.
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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