Can a couple be legally separated and still live under the same roof?
Question Details: Husband lives in a separate space such as a finished basement or in-law quarters within the same household as the wife and children.
Yes. However, try to document it as much as you can though.
For example, you can send an email saying that I will live in basement as agreed. You can open a separate bank account. You can invite couple of friends or family members and tell them clearly that you are living separately.
Building record and documenting fact is critical in any legal situation.
A "legal" separation only occurs when the parites either execute a Separation Agreement, or are granted a Limited Divorce from the court. Just living in differnet places under the same roof does not establish "legal" separation. To proceed with an absolute divorce, one of you must leave the marital home to establish an official date of separation.