Tenant offering to do washroom renovation for free?

[Sheng Rao]

Hi all, hope everyone is doing well.

I am a small multifamily landlord based in Toronto, Canada. Recently one of my tenants asked me if she can hire a contractor to renovate the washroom tiles as she wants to make it look nicer. She said the renovation will be done at no cost to me.

At first I thought oh why not, free renovation. But the more i think about it, the more problems i can think of. What if during the renovation the contractor damages something, and what if the tile work is not done properly and there are future problems (i.e. leaks, cracks). 

Has anyone on BP forum come across this before? What type of legal contract would you sign to protect yourself from potential liabilities?

Thanks!!