The National Fire Protection Association (NFPA) writes model codes which are adopted, usually with minimal changes, by many cities and some states. Included in these codes are 1122, Code for Model Rocketry, 1125, Code for the Manufacture of Model Rocket and High Power Rocket Motors, and 1127, Code for High Power Rocketry. While NFPA charges a high price for paper copies you can view them online at their web site. The viewer is designed so that you can't save what you view but it is possible to capture images if you wish.
NFPA 1122 and 1127 are revised on a regular schedule and are used as the basis for the NAR model and high power safety codes. In general you should consider the NAR safety codes to be condensed versions and the NFPA codes to be the authoritative reference.
There is a lot of detail in the codes that I will not get into. What I will discuss are the storage requirements.
NFPA 1127 requires that you store rocket motors and reload kits that are subject to 27 CFR Part 555 (ATF regulations) in a type 4 magazine. This is a fairly redundant requirement as this is required by federal laws and regulation. But now that all APCP high power motors are exempt from ATF regulation this requirement does not apply. For high power motors exempt from ATF regulation, NFPA 1127 requires simply that they be stored in a "reclosable noncombustible container". This is very simple to do and I purchased a basic metal tool box to use for this. I may have to get something else now that all of my high power motors will have to fit. They do at the moment but one impulse purchase will overflow it.
NFPA 1122 also has storage requirements for model rocket motors. While it does not have any requirement on how you store them, it does have limits on how much. The limit is 50 lb (net) in a residence but with no more than 25 lb. in the living quarters. For anything more than that you have to consult with your Authority Having Jurisdiction.
You can read a little more detail on the situation here in Arlingon, TX.