Change in elevation between Nosing and Landing

[Bruce Ramsey]

New construction. Builder is claiming that the manufactured nosing that matches the laminate flooring is Ok to install so that there is a 1/4" -3/8" difference in height between the nosing and the landing/flooring. I can't find anything specifically saying the nosing must be level with the adjacent flooring or landing in the ICC. Builder is saying he will provide the install instructions but haven't seen them yet. I feel it is unlikely the flooring manufacturer install instructions say to have a lip/ change in height difference. Any pointers?

[Jerry Peck - Codeman]

From the IRC:
- R311.7.7 Stairway walking surface.
- - The walking surface of treads and landings of stairways shall be sloped not steeper than one unit vertical in 48 inches horizontal (2-percent slope).
- - - Exception: (exception addresses drainage, which is not applicable to your question)

For treads less than 12" in depth, this addresses the issue even though it dies not directly address your question: place a level on the tread at the back of the tread (back to the closed riser on closed river stairs) and rear it on the nosing (which is the front of the tread):

a) if using an electronic level, read slope in % or inches per foot (codes states both, however, 1 in 48 = 1/4" per foot, where as 2-percent = 1 in 50)

b) if using a traditional bubble level, adjust the level to indicate level, then measure down to the tread at the back of the tread (<1/4" between the level and the tread exceeds the code slope)

A person with large feet, or even average feet wearing boots, will likely be standing on the tread with heel down on the tread and toe up on the nosing - like the electronic level.

There is, I recall, another code section which addresses floor elevation changes (for non-dwelling units, that is in the accessibility code, I'd have to look it up for in dwelling units - but I never found one of those installations in dwelling units which was within the 1/4" per foot / 2% allowance because all were at least 1/4" height difference in a dwelling unit tread, which is always less than 12" deep ... even non-dwelling units only require an 11" deep tread).