I am a cat owner, and if you have a good sense of smell, you can't really avoid the smell, no matter how often you clean. All homes that have animals have a smell.
You can't avoid some smells but the strong ammonia odor of urine is usually easy to avoid if the cats are well trained and the litter is changed/cleaned regularly. I think the most common reason that it smells are cats that are spraying/marking which isn't always something up to the owner.
