If you want to learn all of the residential stair codes, you are in the right place!
In this guide, you'll learn...
- The top 15 key staircase code requirements
- Minimum handrail height code
- Stair landing code
- Tread depth and nosing codes
- And much more
As a home inspector, I have seen a lot of bad stairs in my life! Stairs without railings, too high of a step, stairs too narrow, and the list goes on.
Staircase codes for residential homes can get pretty complex, and there are numerous exceptions within the International Residential Code as well as state codes that can take priority.
Nevertheless, I have compiled the ten most important stair code requirements with some helpful pictures below.
Let's get started with this stairway code guide!
Last Word For Stair Code Is Local Authority
Always remember that the staircase code of your state and county or city will almost always take priority over national or international code standards.
The stair codes in this article are based on the IRC or International Residential Code handbook — specifically in the Stairways section and Guards section of Chapter 3.
The IRC is a model code standard that has been adopted by many U.S. states for residential properties of 1 to 2 family dwellings. Commercial properties typically follow the International Building Code (IBC). The IRC is updated every 3 years.
15 Residential Stair Codes
Handrail And Guard Code
- Handrail Height Is Between 34-38 Inches
- Handrail Distance From Wall 1-1/2" to 4-1/2"
- Handrail Grip Size Is 1-1/4" to 2" in Diameter
- Handrail Required On One Side If 4 Or More Risers
- Distance Between Two Railings Is Minimum 27 Inches
- Guard Required If Dropoff Is 30-Inches Or More
Riser, Tread, And Nosing Code
- Minimum Stair Tread Depth Is 10-Inches Long
- Stair Riser Height Is Maximum 7-3/4 Inches
- Open Risers Shouldn't Allow 4" Sphere
- Stair Riser Height Is Maximum 12.5 Feet
- Nosing Depth Between 3/4" and 1-1/4"
Miscellaneous Stair Codes
- Minimum Stair Width Is 36 Inches
- Head Clearance On Stairs Is Minimum 6'8"
- Stair Landings With Max 2% Horizontal Slope
- Lighting Required If 6 or More Risers Using 3-Way Switch
Height For Handrails Is Between 34-38 Inches
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.
The exterior stair railing code requirements have mostly the same code as indoor stairs (same riser and tread dimensions etc.) except that the composite materials used for deck stairs must conform to ASTM standards.
Read Also >> What Are The Range Hood Venting Codes?
Handrail Distance From Wall 1-1/2" to 4-1/2"
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.
Read Also >> What Are The Code Requirements For Crawl Spaces?
Handrail Grip Size Is 1-1/4" to 2" in Diameter
The handrail requires a minimum 1-1/4″ diameter and a maximum 2″ diameter if it is circular in shape.
If the handrail dimensions are 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.
Handrail Required On One Side If 4 Or More Risers
If there are four or more risers, then at least one side of the stairs needs to have handrails. Stair railings are very important to home inspectors, and I have called out numerous stairs that violate stair railing code such as missing handrails.
Distance Between Two Railings Is Minimum 27 Inches
The minimum distance between two parallel railings is 27 inches.
If there is only one railing, then there should be a minimum 31 inches from 1 railing to other wall.
This distance is measured from the edge closest to the wall of each railing. This building code ensures that there is enough space for occupants to walk in-between the railings.
Read Also >> What Is The Code For Toilet Clearances?
Stair Guards Required If Dropoff Is 30-Inches Or More
Horizontal stair guards must be installed if the height from floor to edge of stairs is 30-inches or more.
The guard must be at least 36-inches in height.
Minimum Stair Tread Depth Is 10-Inches Long
The standard tread depth for stairs (horizontal portions) should be at minimum 10-inches long.
The longest tread versus the shortest tread should be no more than 3/8-inch.
Stair Riser Height Is Maximum 7-3/4 Inches
Riser height should be 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.
Open Risers Shouldn't Allow 4" Sphere
If the stairs have open risers, then anywhere above 30″ from the floor should not permit a sphere of 4-inch diameter to pass through.
In the home inspection world (and stair risers code), 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.
Read Also >> What Is The Code For Water Heater Installations?
Minimum Stair Width Is 36 Inches
The code for stair width (above the handrail and below the ceiling) requires that the stairs never be less than 36 inches wide.
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, the stairway width code states that the minimum width of the rails should be at least 27-inches below the handrails.
Head Clearance On Stairs Is Minimum 6'8"
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.
Headroom is the space required from the stairs to the ceiling. Basically, this rule helps prevent people from 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.
Read Also >> What Is Building Code For Bathroom Fan Venting?
Stair Riser Height Is Maximum 12.5 Feet
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.
Vertical rise is the total height of the stairs as measured between floors or landings.
Nosing Depth Between 3/4" and 1-1/4"
According to the IRC, the nosing shall have a minimum depth of 3/4″ and a maximum depth of 1-1/4″ depth.
The stair nosing is the portion of the tread that sticks out beyond the riser. Stair nosings usually have a circular or beveled edge.
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.
Read Also >> What Is The Code For Dryer Vents?
Stair Landings With Max 2% Horizontal Slope
The horizontal slope of landings shouldn’t be more than a 2% slope gradience.
The width of the landing must not be less than the width of the stairs.
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.
Lighting Required If 6 or More Risers Using 3-Way Switch
Stairs must be illuminated with a switch at the top and bottom of stairs if there are 6 or more risers.
Stairs are perhaps the most dangerous location in a home, and lighting is needed to keep occupants safe. 3-way switching allows people to turn the lighting on and off from either the top or bottom of stairs.
Frequently Asked Questions
What is the point of staircase codes?
The building code for stairs is primarily to keep occupants safe, avoiding injury and to make for a speedy escape in case of a fire or other emergency.
What are the building codes for rise and run?
The code for rise and run of stairs is a maximum height of 7-3/4 inches of rise with a minimum run of 10-inches. There also shouldn't be more than a 3/8-inch difference between the treads and risers.
Can I use 2x10 for stair treads?
It is allowed to use either 2x10's or 2x12's to build residential stairs. The stair stringer needs to support the load of the stairs and be at minimum 3.5-inches wide.
There you have it, the basics of the stair code requirements. 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 IRC.