Staircase code for residential homes can get pretty complex, and there are numerous exceptions within the IRC handbook as well as state code that can take priority.
Nevertheless, I have compiled the ten most important stair code requirements with some helpful pictures below.
In this HomeInspectorSecrets.com Guide, I will go over:
- The top 10 key staircase code requirements
- Minimum handrail height code
- Stair landing code
- Tread depth and nosing codes
- And much more
Let's get started with this building code guide!
What Is The Residential Stair Code?
For residential homes, staircase code is laid out in the IRC or International Residential Code handbook in Chapter 3.
The IRC is a model code standard that has been adopted by many U.S. states for residential properties.
The International Residential Code is updated every 3 years. Always remember that the staircase code of your state and county or city will almost always take priority over the IRC unless the IRC has been totally adopted.
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Residential Stair Code (2022 Requirements)
- Minimum Stair Tread Depth
- Stair Riser Height Code
- Minimum Stair Width
- Head Clearance On Stairs
- Stair Riser Height Code
- Stair Landing Code
- Handrail Height Code
- Handrail Projection, Clearance, and Continuity
- Handrail Grip Size
1. Minimum Stair Tread Depth
The treads (horizontal portions) of a stairs should be at minimum 10-inches long. The longest tread versus the shortest tread shouldn’t be more than 3/8-inch.
2. Stair Riser Height Code
Riser height should have a maximum height of 7-3/4 inch height (4-inch minimum). 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 the 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 the ground.
3. Minimum Stair Width
The minimum stair width above the handrail and below the ceiling shouldn’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 are handrails on both sides, then the minimum width of the rails should be at least 27-inches below the handrails.
4. Head Clearance On Stairs
Headroom is the space required from the stairs to the ceiling. Basically, this rule helps prevent people banging their head when using the stairs.
This rule will more likely be an issue on older homes that I inspect, and they are usually grandfathered into existing code due to 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.
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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.
5. Stair Riser Height Code
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.
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.
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7. Stair Landing Code
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 be less than the width of the stairs.
Also, the horizontal slope of landings shouldn’t be more than a 2% slope gradience.
8. Handrail Height Code
Stair railings are very important to home inspectors, and I have called out numerous stairs that violate stair railing code such as missing 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.
Theexterior stair railing code requirements has mostly the same code as indoor stairs (same riser and tread dimensions etc.) except that the composite materials used for deck stairs must conforms to ASTM standards.
9. 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 like fleeing a fire.
10. 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.
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What Are Common Residential Stair Code Violations?
During my home inspections, the most common areas that I cite in regards to stairs come down to just a few items:
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.
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.
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.
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.
Final Thoughts On The Residential Stair Code
There you have it, the basics of the 2021 IRC stair code. And again, the IRC is updated every three years, but usually the basic step 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.