ZoE will be 9 months old this Friday and has had the run of the house since she was 4 months old. Thankfully, she's completely potty trained. The only rooms I close the doors to are the guest bedroom and the bathroom.
I started her off in a playpen as a pup and that didn't last long because she quickly figured out how to scale the walls of it. I was worried about her getting hurt falling over the top, so that went in the basement storage room within days of getting it.
Then I used a tall gate to confine her to just the kitchen, dining room & living room areas, which are all open to each other, and put her potty pads infront of the gate. Once I was sure she was potty trained, the gate came down and the potty pads were moved just a few feet into the part of the hallway that deadends at the stacked washer/dryer laundry closet, which is right across from the bathroom so its convenient to flush her poops! It works great for us
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