When the tenants have caused damage to the property and refuse to repair it, you can serve them with a Form N5 which is the legal notice based on damages. It’s a 20 day notice which allows the tenant to correct the problem within the first seven days and if not then you can apply to the Landlord and Tenant Board. This form can be downloaded from the Board’s website at http://www.sjto.gov.on.ca/ltb/forms/