While typically you would use a basement as an extended living space accessible from the floor above, there are situations where you may only use it for storage and might wonder if you can remove the existing stair, or simply build a new basement without a stair.
There is no code requirement for a basement to have a stair. However, if removing an existing stair, you need to ensure that it is not being used as a means of egress for emergency situations. If it is, you may need to find a way to create a new or alternate means of egress in order to replace the stair.
Keep in mind that in addition to the number of exits required from a floor, you also need to ensure that the exits are sufficiently separate (in terms of distance) in order to comply with the code. Keep reading as we’ll cover this in more detail.
How Are Basements With No Stair Accessed?
Basements that do not have stairs can only be accessed through an egress door. This usually means that the basement is only partially submerged below grade and often the path to the entrance door is excavated to allow for access.
An alternative to the traditional door sometimes used in basements, or more likely cellars, is the bulkhead or hatchway door. This provides access to the basement or cellar at ground level without the need for grade excavation. Hatchway doors usually lead to access stairs down to the basement floor. They are typically found in older homes.
Hatch doorways can be used internally as well as on the outside of a home. It’s important to note that these hatchway doors are for convenience access only, they do not provide a legal means of egress if the basement space is used as a habitable space.
Do Basements Need Two Exits?
The short answer is, it depends. If the basement is used as a habitable space, that is, if there are bedrooms, family rooms, game rooms, or other types of living areas, then you do need to have at least two exits out of the living spaces. This is to ensure emergency escape in situations where one of the exits is inaccessible due to fire or other catastrophes.
This information is based on the International Building Code (IBC) which covers most of the United States. Be sure to check your local building codes, however, as you may live in a part of the country that uses a different code are has supplemental codes in addition to the IBC.
Exits can be provided either through exit doors, windows that meet code requirements for egress, and stairs that are specifically designed to serve as an exit from within a floor. If the other two means of egress are not available, then a stair may be required for the basement.
Remote Distance Requirements
In addition to the number of exits, there are also requirements for their location. Because they are critical as a means of egress in case of a fire or other catastrophe, exits need to be separate enough so that if one exit is compromised the other is available to use. Having exits too close together defeats this purpose, so that’s where remote egress requirements come in.
While codes can vary in this regard, the most commonly used metric – which is also what the IBC code specifies – is half the diagonal distance of a space for egress separation. The measurement is taken from one corner of a room to the opposite corner, divided by half, and the resulting distance is the required separation from the center of the first egress door or window to the center of the second.
Some codes will also specify a minimum distance, such as 50 feet for example so that if half the diagonal is less, the larger minimum distance is required. In the case of stairs, the required egress distance is determined from the base of the stair, measured from the nearest point of the exit stairway.
Egress Stair Requirements
If used for egress, egress stairs need to meet certain criteria. The width of the stair needs to meet the minimum requirements set by the code. Usually, this amounts to 3 feet in width (IBC) for residential homes. Additionally, the length of the treads and the height of the risers need to be uniform and meet the maximum or minimum dimensions stated in the code.
Below is a table that outlines most of the stair requirements for an egress stair. This data is based on the International Building Code (IBC) requirements, so be sure to check with your local codes in case your jurisdiction uses a different code.
Egress Stair Components:
|Stair width||3′-0″ (914)||Minimum width for residential structures|
|Stair tread depth||10″ (254)||Residential only. Distance from nosing to nosing|
|Riser height||4″-7 3/4″ (102-197)||Residential only. Minimum and maximum height|
|Variance||3/8″ (9.5mm)||Between smallest and largest within any flight|
|Minimum headroom||80″ (2032)||Minimum headroom at any point|
|Maximum flight||12′-0″ (3658)||Maximum vertical rise between floors or landings|
|Nosing projection||1 1/4″ (12.7 mm)||Allowable nosing projection beyond riser|
|Guardrail height||34″-38″||Residential homes. Required at openings|
|Baluster spacing||4″ (102)||Maximum spacing between balusters|
So far we’ve discussed stair requirements based on the building code. There are situations where a stair is not mandated by code, but having one provides a convenience for accessing the basement. Convenience stairs, also referred to as monumental stairs in the code, are not subject to the same requirements as those used for egress.
For example, the location of the stair is entirely optional. That is, it can be placed anywhere. Additionally, while egress stairs must have closed risers, a convenience stair is allowed to have open risers as long as they are less than 4″ in height (do not allow a 4″ sphere to pass through).
When evaluating whether or not you should build a basement stair or remove an existing one, you’ll want to take this into consideration. If you need to access the space during the winter, for example, does it make more sense to go outside to use the basement or access it directly from the inside of your home?
Whether a stair is required in a basement depends to a great extent on the use of the space. If it is used for storage purposes only and there is a way to access the space through either a standard door or a bulkhead (hatch) door, then a stair will likely not be needed.
If on the other hand the basement is used as a living space, there is a good chance that the stair may be needed for egress if there are no additional legal means of egress out of the space. As mentioned in this article, habitable floors require a minimum of two means of egress for emergency exit.
It’s important to note that while there are specific code requirements that can affect whether a stairway is needed, there is also a practical side to having a stair for easier access. So, even if the code does not require a basement stair, it may very well be that it provides a convenience of access that would otherwise not be available.
Building Codes Illustrated, Francis D.K. Ching and Steven R Winkel, FAIA
International Code Council, International Building Code (IBC)
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