Does the code you’re working under have anything to say about maximum nosing projection and treatment of the bottom edge of the nosing? For example, IBC 1011.5.5.1 states a maximum 1.25” nosing projection and A117.1 504.5 states the underside of the projection must be curved or beveled. Limiting the depth and providing a bevel or curve would help prevent a boot from getting stuck.After much searching I am unable to find a code stipulated maximum dimension for the tread thickness, I find it strange as especially with Part 9 open risers if the tread was too think you could get a boot stuck in there!
I think that it is more about legs.a child could fall thru
Not to go too far down the rabbit hole but the 4" rule I understand is primarily to prevent small kids getting the head stuck, I have three boys.... I've seen it all!!I think that it is more about legs.