The guard height must be at least 42 inches high, and it is measured vertically from the leading edges of the tread nosings or from the landing surface. IBC 1009.11.7 Stairway projections. However, the very minimum width between handrails is 44 inches. Where the stairway has a straight run, the landing does not need to be more than 48 inches deep. See code requirements for nosings, riser designs, uniformity and additional exceptions. To read more on this topic, see our Ask an Expert post When framing a stair landing, questions often arise on the proper way to install a landing beam or floor joist that is making a membrane penetration of a rated wall assembly for the stair enclosure. Several components are looked at such as stair width, headroom, riser and tread heights.Note that when looking for residential stair standards, one must look at the International Residential Code (IRC). On 2018-07-01 - by (mod) - risk of moving steps due to frost or waterMy opinion is that if the slab is connected to the foundation on the foundation is protected from frost movement then you still could have step movement if water enters under the slab and if the garage area is not hated. The International Codes (I-Codes) are the widely accepted, comprehensive set of model codes used in the US and abroad to help ensure the engineering of safe, sustainable, affordable and resilient structures. But the step down hazard remains regardless.

Concerns about safe use by children or the elderly do not apply.

Thank you for the information. Regarding structural design criteria, 2018 IBC Table 1607.1 (30) requires stairs to resist a minimum live load of 300 pounds (concentrated load) or 100 pounds per square foot (psf), or 40 psf for one one-and two-family dwellingsIn contrast to this approach, some designers prefer to use the notched stringer as a form to attach riser and tread boards, and to sister another full-depth piece of dimension or engineered lumber to the side of the stringer to serve as the structural member.An approach for narrower stair sections is to keep the two outer stringers whole (unnotched) and provide a wood-bearing block or manufactured steel angle on the inside face beneath each tread. They must also be no less than three feet long. Extension shall return to a wall, guard, or the landing surface, or shall be continuous to the handrail of an adjacent stair flight.

Inconsistencies or variations in risers or treads could interfere with the rhythm of the individual using the stairs. R311.5.4 Landings for stairways. The four rim joists of the landing are on the outside of the posts and are only being held up by the fasteners alone. inches (914 mm) measured in the direction of travel. The headroom clearance for commercial stairways measured vertically from a line connecting the edge of the nosing should be no less than 80 inches. Design of stringers, treads, and their connections are left to the structural engineer. The minimum width for stairways shall not be less than 36 inches clear. Exception 1 in Section 1005.3.1 allows for a reduction in size when a building is equipped with an automatic fire sprinkler system and an emergency voice/alarm communication system, except for when serving an occupancy group H and I-2.When a building is equipped with these features the factor used when determining the width for stairs is reduced to 0.2 inch per occupant.For example if we take the same example above, the calculated width would be 40 inches (200 x 0.2), but of course as stated above a minimum width of 44 inches must be used. With the above example we had to calculate the stair width, but with this exception you can have the stairway width be as small as 36 inches as long as the occupant load it is serving is less than 50.It is important to know that these requirements are for stairs serving as a means of egress.