Older Dog Housebreaking

Question
In March I adopted a 15-month-old female Cairn terrier rescued from a breeding kennel. She had been fostered with others dogs using a doggy door.  I do not have a doggy door but she has access to the deck/backyard when I am home and she can let herself in and out. She does not like to get off the deck and sometimes pees and poops on the wooden deck. This is OK with me because at least it's not in the house. However, she can't seem to make the connection between going outside and doing her business out there. She will come back in the house and do it. What am I missing.....there must be some way to get her to make this connection, but I'm out of ideas. I've tried taking her out in the yard on a leash, getting potty pads to put on the deck, taking her out first thing of a morning and after eating and at night, but nothing has worked. Thanks for any help you can give.
Suzanne Carney

Answer
For nearly 15 months this dog has pretty much been allowed to potty wherever/whenever the urge hit her. You need to pretend you just brought home an 8-week-old puppy and start from scratch, with no assumptions that she knows anything.

Get a crate for her, and keep her in it when she cannot be watched, when no one is home, and at night. Take her outside after she wakes, eats, and every couple hours throughout the day. Go outside with her so that you can observe her going, and praise her enthusiastically when she does. If you think she should have to potty, and she doesn't, put her back in the crate and try her a half hour later. Keep a journal of her potty habits so that you know when she should need to go.

Work hard and consistently at this and she should improve. Right now she just doesn't have a clue.