The Liberal Party has promised changes to granny flat regulations so homeowners can rent them out to people outside their families.

At the moment, granny flats in most local government areas can only be occupied by relatives or the homeowners themselves.

The Planning Minister John Day says the move would create more affordable housing across the state.

"That will help students, fly in fly out workers, carers, seniors, single people to have a greater range of options available in relation to rentals," he said.