To answer a quick question, I cannot understand why you think that you need to de-normalise the data.

An ERD is (or should be) created BEFORE the database. The DB definitions are based upon the ERD and thus the original ERD (or a very close approximation thereof) can be logically deduced from the DB design.

The table positioning and type of the foreign key constraints will show the type of relationship between two entities, though be carefull with those tables which links two others to provide a many to many relationship.