Landlord liability

Hi there. Does anyone know where we would stand as a landlord, if our tenant was to carry out some maintenance work on our property. He’s a roofer and says something needs fixing on our roof. He’s happy to do it and says it’s an easy job for him but here would we stand if he had an accident - God forbid!
Anyone know?
Many thanks

then put it in writing that he is liable for his own work. I suggest you employ him to do the job ,get a written quote and pay thus no liability on you