Cat Odor in the house

[Khurram Bashir]

My tenants had multiple pet cats which had left a real strong smell and  odor in the house. House has wooden floors on which i can see signs pee which has turned black over time. 

I plan to sell this house after repair, real estate agents tell me that it is impossible to remove the odor.

Andy suggestions to remove the odor would be really appreciated. 

[Terrell Garren]

Pull up and replace the damaged flooring. If the subfloor is damaged, mop with bleach mixture, cover with 2 coats of Kiltz and one coat of transparent sealer. Fresh wall paint wil help hide any remaining smell.