Our basement has a sloped barn-style door that opens to a patio. I want to put a sort of a deck on the patio and thought I would put a flat trap door over the basement opening. The basement is used only for storage. Is there a code requirement or reason why basement doors are sloped? What are the requirements for a basement door?
Basement doors (also called a "bulkhead door" in some parts of the country) is sloped to shed rain/snow. They usually cover a stairway. It also serves to keep critters out of the basement.
A trap door should work fine. It would be fairly heavy so you might want to consider some sort of counter balance system or at minimum a way to hold it open so it does not fall on someone while open/in use.