If 6 months u already should know it's gone case. So take the extreme option. Tell them u sold the house and renovation will start soon.

For landed:

Give 1 month notice, renovation will start on xx date.

Rent a bin and put in car porch or block entrance.

Buy sand and cement bags from nearby hardware store. Ask them deliver to the house , put at car porch. Remove all utilities.

For condo:

Inform management block the cards. Say wan do renovation, give deposit and get the renovation permit.

Tell them house sold, want to do renovation. Give 1 month notice. Stick the renovation notice on the gate.

If they hvnt start moving, hire some friends to act as contractor say want go into the unit to check and do renovation.