Litter Box Help!

I have a 3 year old female tabby who was a ferrel (sp?) kitten - we saved her life when she was 8 weeks old. She has never been able to use the litter box correctly - she poops on top (which i know is normal and ok), but then she scratches the sides of the litter box and the wall of the shower (I have their box in a square shower so it's private and easy to clean) for 1-3 minutes, depending on her mood. She wakes us up every night with this behavior and only responds when i go into there and say "Grace! No Scratch!" Then she gets out. What to do?????????? HELP Please!

Thanks in advance!

I have no advice other than to tell you that you aren't alone. My little girl Ophelia, who we also rescued as a feral kitten when she was about 6 weeks old (she was trapped in between the walls of our apartment building, and we couldn't find Mom), does the same thing. Although, she does cover her stuff in the litterbox, she scratch scratch scratches on the floor around the box. She doesn't do it as long as your Grace, probably 30 seconds to a minute, but she does it nonetheless.

Yup, our feral rescue Scarlett has always done the same thing (for a minute or 2). I always thought she was just trying to be fastidious.

Buy a section of astroturf to fit the inside of the shower (easily removeable) after a few times of scratching the turf, they quit.

Adding another that does this! After she's done her business, Kayla VERY enthusiastically scratches, scratches, scratches, sometimes to cover. She doesn't distinguish between the litter and the floor/walls (and she scratches pretty high up too!). Sorry, I don't have any suggestions for you since I never tried to stop it. I just found it highly amusing to watch and didn't think it a prob.