Hi, I am family day care educator. I would like to have advice on safe floor mattress using for toddlers. I prefer all my children ( over 12 month old) sleep on the floor mattress. Do you have any safe guides for floor mattress which I can refer to? I could not find specific requirements for floor mattress such as: what is the required thickness? Is waterproof mattresses required in childcare setting? Thank you

There are no specific guidelines related to thickness of floor mattresses in child care services (including FDC).
Generally floor mattresses would be much thinner than a standard cot mattress & it should always be firm.
Red Nose recommends that all mattresses should be firm, clean, well-fitting & flat.

Red Nose (& other safety organizations) recommends sleeping baby in a cot that meets the Australian Standards, until at least 18 months of age.
https://rednose.org.au/article/where-to-sleep-a-child-who-has-moved-from-a-cot

For safety reasons, when a young child is observed attempting to climb out of a cot and looking like they might succeed, it is time to move them out of the cot.
This usually occurs when your toddler is between 2 and 3 ½ years of age but could be as early as 18 months
https://rednose.org.au/article/making-your-home-safe-before-moving-a-child-from-a-cot-to-a-bed

If a service is using a floor mattress for any baby or child, then the safety of the baby/child in that particular room is important & needs to be highlighted in Sleep & Rest Policy.
It might be helpful to talk to your local Regulatory Authority about this as well.
https://www.acecqa.gov.au/help/contact-your-regulatory-authority

It would be important to include the safety information in the cot to bed brochure (attached) suggested for babies/toddlers once they have moved from a cot, in your policy for younger babies on floor mattresses.