When it comes to residential stair standards, the International Residential Code (IRC) establishes minimum requirements for stairs to insure a level of safety to the public. Several components are looked at such as stair width, headroom, riser and tread heights.
Note that when looking for commercial stair standards, one must look at the International Building Code (IBC). In this post we will be looking at the code standards related to residential stairs in accordance with the International Residential Code (IRC).
Now let’s get into what those residential stair requirements are…
The minimum width for stairways shall not be less than 36 inches clear. Now when handrails are introduced they shall not project more than 4 ½ inches on either side. Therefore if a handrail is provided on one side, the clear width of the stairs shall not be less than 31 ½ inches and when handrails are provided on both sides, the clear width shall not be less than 27 inches.
HEADROOM AND VERTICAL RISE
Headroom for Stairs
Having proper headroom is another important code requirement. The headroom for stairways measured vertically from the sloped line adjoining the tread nosing or the floor surface of the landing should be no less than 6 feet 8 inches.
Vertical Rise for Stairs
Stairs cannot be continuous without have a landing or floor level that breaks up the flight of stairs. The height limit established by code is intended to provide a reasonable interval for the user so that they may rest on a level surface and to alleviate the negative effects of long uninterrupted flights.
The code establishes a maximum vertical height of 147 inches (12 feet 3 inches) between landings or floor levels for a flight of stairs. If the distance between floor levels exceed 147 inches, the flight of stairs would require a level landing somewhere in-between to break up the flight of stairs.
STAIR RISER HEIGHT AND STAIR TREAD DEPTH
Stair riser heights and stair tread depths should be within the parameters of the code to avoid any potential trip hazards for inconsistencies. A uniform flight of stairs provides a safety factor. Inconsistencies or variations in risers or treads could interfere with the rhythm of the individual using the stairs. Therefore limitations in riser heights and minimum widths for treads is an important rule to follow.
Stair Riser Height
The code specifies that risers should not be more than 7 ¾ inches in height and that any variation of risers within a flight of stairs should not be more than ⅜ inch. Note that dimensions here should be taken excluding carpets, rugs, or runners.
Stair Tread Depth
As for stair treads the depth should not be less than 10 inches however this will require nosing projections. To avoid having to install nosing the code requires the depth of the tread to be no less than 11 inches. Nosing that is beveled should not exceed ½ inch or the radius of curvature not more than 9/16 inch. The projection of nosing shall not be more than 1 ¼ inches and no less than ¾ inch. Again the tolerance of treads or nosing should be no more than ⅜ inch.
Handrails? Who can forget those?
Residential Handrail Code Requirements
When it comes to handrails the code is very specific on this. It should provide proper graspability which the code recognizes a Type I and Type II handrail to have.
Type I handrails layout the parameters for handrails having a perimeter dimension not greater than 6 ¼ inches while Type II handrails address handrail perimeters greater than 6 ¼ inches.
Stair Handrail Height
As for their height they can be placed within 34 to 38 inches and shall be provided on at least one side of a flight of stairs having four for more risers.
If they are placed up against a wall they should have a clearance from the wall not less than 1-½ inches.
They must be continuous for the full length of the flight of stairs and shall begin at a point directly above the bottom riser to a point directly above the top riser.
Finally, just an important side note. Many people commonly confuse a handrail from a guardrail and vice versa. To learn about the code requirements for Residential Guardrails and what purpose they serve, be sure to check out this POST.
So this basically sums up the basic code requirements for residential stairs and their dimensions. Therefore let us recap on the residential stair code requirements:
- Minimum 36 inch clear width for stairway.
- Maximum 4-1/2 inch handrail projection into stairway width, on either side.
- Minimum 6′-8″ headroom height clearance for stairway.
- Maximum 12′-3″ vertical height (rise) for a flight of stairs.
- Maximum 7-3/4 inch stair riser height.
- Minimum 10 inch stair tread depth with nosing or Minimum 11 inches with no nosing.
- Handrail graspability to be either Type I or II with a Minimum 1-1/2 inch clearance from a wall.
- Handrail height to be placed a Minimum 34 inches to 38 inches.
For more information, see Section R311.7 of the 2015 International Residential Code for a more in-depth look at stair requirements.
* Reference Source – 2015 International Residential Code – [Buy on Amazon]