since 2002 the main access to the dwelling is supposed to be accessible for people with disabilities.
Certain engineers / architects have 'signed off' other doors as being sufficient, but technically they are incorrect to do so.
To approach your question from another angle, a 9" (228mm) high step in a domestic house is 8mm too high, the max allowed is 220mm and you have 228mm... but whether its 'substantially' in compliance is up to your certifier... personally i would not have an issue with 8mm.