If you're not sure of how the OHSA regulates the relationship between you and your sub-contractors don't worry, the Health & Safety Advisor has an explanation for you.
Sub-contractors are your employees under these circumstances
According to the Health & Safety Advisor, difficulties can arise when courts ask you whether your sub-contractors are self-employed or direct employees of your business, relating to matters outside safety.
That's why it's advisable in terms of health and safety to treat self-employed and labour-only sub-contractors the same as your employees.
Remember, Section 37 of the OHSA regulates the relationship between you as the principal contractor and your sub-contractors
Your sub-contractors must ensure that their employees– especially supervisors and operators of machinery, vehicles and plant – are aware of the safety obligations placed on them by contract, as well as under statutory and common law.
Make sure your sub-contractors comply with these three safety obligations.
Please note that although a sub-contractor is your responsibility if you're the principal contractor, he's still an employer in his own right.
This means both you and your sub-contractor are responsible for your employees, but your sub-contractor's employees become your responsibility when you've employed them yourself.
The bottom line: Treat your sub-contractors the same as your employees and ensure your sub-contractors comply with the same moral, legal and mutual obligations as you to successfully carry out any contracts you've been awarded.