I have a dog run (pea gravel) on the side of my house, then a few stone
steps, then 2 steps up to a redwood deck. My dogs have the run of the deck
and sleep on the covered portion. Right now, my dogs, a Labrador Retriever
and a Yorkshire Terrier, do their business in the dog run and not on the
deck.

I'm worried that when I replace the raised redwood deck with a ground level
concrete (or other hard material) patio that the dogs will start using it as
a bathroom. Is this likely? Is there a way to make a successful transition
so they will recognize the patio as their new home and continue to use the
dog run as the bathroom?