Tenant keeps making improvements on the house

[Dina Abbott]

I am renting a house to a tenant that keeps making improvements to the house. He put in a backsplash in the kitchen, put up larger fence doors, light fixtures and fans, etc. I keep telling  him to stop and he says dont worry about it, you wont owe us anything, we just love the house. I did pay for new flooring in the house and he put it in himself which I am paying him by taking money off rent $350 for 5 months. Now he wants to replace the shed. I finally told him to stop doing it and that no, he cannot do that. He got all huffy and puffy and said that he may just go buy a house etc, he said we dont owe him anything but then contradicted himself and said: " do you know how much money I spent here"? I was planning on renewing the lease, which is 3 months away. What should I do? Any specific language that I can include in the new lease? These improvements need to stop. Thank you