Full details can be found here:
The Defendant (the person being sued) has committed adultery with another person (the Co-Defendant) and the Plaintiff finds it intolerable to live with the Defendant.
The Defendant has behaved in such a way that the Plaintiff cannot reasonably be expected to live with him/her.
The Defendant has deserted or left the Plaintiff for a continuous period of 2 years without any intention of returning.
Separation for 3 years - WITH CONSENT
The Plaintiff and Defendant have lived apart for a continuous period of at least 3 years and the Defendant agrees to a divorce.
Separation for 4 years
The Plaintiff and the Defendant have lived apart for a continuous period of at least 4 years. No consent is required from the Defendant.