their house

Are we supposed to assume it's the same house as in TBBT? Or a different one? Because the few times we see it on TBBT it seems like it's Sheldon's childhood home, but it's clearly not the one we see on YS. Biggest giveaway is that on TBBT there's an upstairs, and I don't see George and/or Mary just deciding to build on an upstairs after the kids have moved out. I think it's supposed to be the same one, but morphed, like the Myers house in the Halloween movies. But, have to wonder why. The shows are done by the same people so it seemed like they could've retained the set if they wanted. My best guess was a creative decision, thinking that a one-floor ranch style house would feel more '80s Texas.