We had an issue with our upstairs hall carpet when we first moved in to our new house. We were told that the previous owners had kept two rather large dogs in the house - for much of the day it seems. And when we finally moved in and began to paint and redo much of the interior decor, we discovered how much those dogs used and abused the floors. It almost seemed as if the owners never let the dogs out, from the amount of mess that we're talking about.
Now this was a cause for concern obviously, as this was not only a matter of aesthetic appearance, but also health in my mind. I'm talking about the overwhelming degree of dog messes to the upstairs carpets in particular. It even appears that the previous owners had started to replace the carpeting in all three bedrooms just prior to moving. But they left the upstairs hallway and stairs undone so we could see what damage must have been done to all the carpet on the second floor. At any rate, one of our first stops in our indoor renovation of the house was the Carpet Shop.
The carpet was easy enough to replace thanks to the selection and service provided by that shop. But the damage done to the underlying structural wood panels was not. We could only do our best to clean up the stains we could see and hope that there weren't too many others that we couldn't.