Again, I hope someone can share a code reference for the 6" step/curb between garage finish floor and finish first floor for CO sequestering/isolation.
This isn't a matter of controlling nuisance stormwater.
This is the first time I've heard of this requirement...I just did some websearching and found a recommendation that a step or curb should be placed between the living space and garage to control CO and/or gas fumes from entering the dwelling--the information was found on a builder's page, but I need a solid national standard.
Hoagie...it doesn't make sense. CO is deadly. No one in their right mind would try to sequester CO within the building. You try first to not allow its development, and secondly to ventilate adequately to get rid of it.
Further, a 6" step would do little or nothing to mitigate gas migration, even gases that are heavier than air. They would migrate by differential pressure and air currents. Only positive seals will help against gases...a 6" curb, step or other "obstruction" would do nothing for that.
The National Fire Protection Assoc. (NFPA) has standards for detecting and warning against CO, but no standard for sequestering it.
I wasn't referring to errant stormwater. I was referring to the building code requirement for a garage floor to drain to the outside. On the dwelling side, this is usually mitigated by providing a differential slab elevation or "step".
I sincerely hope you do not incorporate this "sequestering" concept in a design. In my humble opinion, to do so it would constitute professional negligence. If you do, make sure your liability insurance premiums are paid.
Many local building codes (admendments to IBC) still require a step between the house door and the garage floor for attached garages.
The original intent of the step was to prevent carbon dioxide and gasoline spills from creating a fire hazard. These scenarios were found not to be prevalent and the requirement in the code for a step was deleted a few years ago by the International Code Council.
The step also makes a compliance problem with the Americans with Disabilities Act.
