How Wide Do Basement Stairs Need To Be?

When building basement stairs, you should see to it that the standard measurements should be complied with, like the stringer depth, stairwell header height, and of course, the width of the stairs. But what is the standard width for basement stairs? Well, we've researched the answer for you.

The standard clear width for basement stairs should be at least 36 inches, measuring horizontally from one edge to the other edge of the tread.

Before constructing basement stairs in your house, you should first know the terminology used and the recommended measurements to properly execute the task and comply with the requirements. Continue reading as we elaborate more on the topic and answer related questions along the way.

A green carpeted basement stair with white painted wall with a small resting area underneath the stairs, How Wide Do Basement Stairs Need To Be?

Basement Stair Code Requirements

The International Residential Code (IRC) has provided requirements for building staircases for one-and two-family dwellings. Code compliance is important since it introduces uniformity and safety.

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Foregoing code requirements will only lead you to a lot of problems—from paying huge fines, putting your family in danger, redoing and disassembling the whole project, to jeopardizing your home sale. So it's always best to know first the basement stair code requirements issued by the IRC.

1. What is the minimum width for a staircase?

As mentioned in R311.7.1, the clear width size of a staircase should be at least 36 inches measuring above the handrail's permitted height and below the headroom's required height.

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The stairway's minimum clear width at and below the handrail height, which includes the treads and landings, shall be 31.5 inches if there is only one handrail installed, and 27 inches if there are two handrails installed on both sides of the stairway.

2. Headroom

According to the IRC, the stairway's headroom should be at least six feet, eight inches. The reason why building codes give headroom allowance for basement stairways is to ensure that your head is safe while passing on the stairs and allow big furniture or items to move through.

3. Vertical Rise

In a flight of stairs, a vertical rise's maximum dimension should be 12 feet, seven inches long.

4. Walkline

The walkline is the usual or ordinary path in your stairway that you typically use. It can be found 12 inches from the interior of the turn, which is measured from the clear stair width's widest point located at the walking surface.

5. Risers

A stair risers' maximum height should be seven and three-quarters inches. The IRC has provided for a maximum riser height to prevent stairs from being too steep when you walk up and down. Since this is a height requirement, all risers must be similar if not identical.

If there are possible variations, the greatest riser height within a flight of stairs shall not surpass the height of the smallest riser by more than three-quarters of an inch.

Since some prefer an open riser, you must make sure that the opening gap between the steps should not be that large that a four-inch sphere could easily pass through.

6. Treads

A stairway tread depth should be measured horizontally from one nosing or outer edge of the step to the adjacent vertical riser just beneath it. It should be at least 10 inches.

As much as possible, the tread depth standard measurement should be followed to allow your foot to have adequate space. So, the treads must be similar, if not identical. And if there are any variations, the greatest tread depth within a flight of stairs should not surpass the smallest by more than three-eights inches.

7. Nosing

A nosing's main purpose is to give extra room for your feet when landing on the tread to ensure safety.

A nosing's curvature radius should not be more than nine-sixteenths of an inch for a bevel edge nosing, it should not be more than one-half-inch. For a nosing projection, a stairway should be provided with at least three-quarters inches and a maximum of one and one-quarter inches.

If there are any variations with your nosings, make sure that the greatest nosing projection shall not surpass the nosing with the smallest projection by three-quarters of an inch within a flight of stairs.

8. Stairway Landing

For a straight stairway, the landing depth should be at least 36 inches in the direction of travel. The landing's width must not be lesser than the width of the staircase which is measured perpendicular to the travel's direction.

Basic Stair Terminology

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Aside from the measurements, recognizing the basic terms used in building a staircase is vital to prevent any errors along the way. Knowing each term will enlighten you on how to properly build a staircase especially if you do build it yourself.


Stringers are usually made up of dimensional lumber. They are located on either side of the stairs which support the riser and tread.

They primarily form the main structure of a staircase. Typically, a stairway will have three to four stringers.

Stairwell Header

The " data-type="URL" data-id="">stairwell header is important since it is the one that supports the floor above and it's also where the stringers are attached.


Headroom is the dimension between the top of the stair treads and the ceiling.


A tread is also called a run and it is the part of the stairs where you step on. It is the horizontal section of each staircase.


If the tread is the horizontal section of a staircase, risers are the vertical part. Risers are the ones on top of a tread. Depending on your choice, some risers are covered or enclosed, while others remain open.

The width and height of treads and risers are the components of each step of your staircase.


Nosing is located at the edge part of the tread that protrudes and extends over the riser below it. Some basement stairways have nosing, while others don't.


Stair landings can either be the space approached on the floor area near the top or bottom tread or a small platform that introduces the change of the stair's direction or connects two stairs.

Total Run and Total Rise

Total run is the stair's overall horizontal length. Total rise, on the other hand, is the total vertical distance from one finished floor to another.

Unit run/stair run

Unit run or stair run is the horizontal distance from the face of one riser to the next adjacent one.

Unit rise/stair rise

Unit rise or stair rise is the vertical distance from the top of one tread to the top of another.

You may check the video below for your reference:

Do basement stairs need a landing?

Every basement staircase, as stated by the IRC, is required to have a landing on the top or bottom part because it is unsafe to directly step on a staircase just once you reach a door opening. Hence, basement stair landings are mandatory.

Interior of an empty basement with wooden stair flooring and white and white painted walls

Do basement stairs need a handrail?

According to the IRC, a handrail should be installed on at least one side of a stairway with four or more risers. Since it is provided by the rules, you must install railings on each side or one side on each flight of stairs.

Check this wooden handrail on Amazon

The Wrap Up

A green carpeted basement stair with white painted wall with a small resting area underneath the stairs

According to the IRC, the recommended standard basement stair width should be 36 inches. It should be measured horizontally from the edge of each side of the stair. As far as safety and comfort are concerned, knowing and following the measurement guidelines is a must.

For more information regarding basement stairs, check these awesome posts below before you go:

How To Insulate Under Basement Stairs

Do Basement Stairs Need A Door?

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