If you were hoping to find concrete content here—or even PDF versions of current staircase standards—I’m afraid I have to disappoint you. Personally, I believe standards should be freely available to everyone, but in Germany things are regulated differently.
In practice, the many standards and regulations make life difficult for stair builders. It’s very complicated to gather information on all the rules that apply to a building project, because they aren’t compiled in one place but scattered widely. The next challenge is recognizing which regulation applies in a specific case. Especially stair builders who don’t exclusively build stairs should, in case of doubt, clarify these questions in writing with the architect and the client—because if it later turns out that the wrong regulation was applied, the executing company, as the professional, quickly ends up being the “fool.”
Typical examples:
“A building staircase must comply with DIN 18065.” → Wrong
“An escape staircase with grating treads only has to comply with DIN EN 14122-3 for ‘industrial stairs.’” → Completely wrong
“In a single-family house you can do whatever you want; you don’t even need a railing.” → Also wrong