Why Are There Room Definition Lines in My House?

My Sim owns a SB. It's not out of his house, but rather on another lot. So, I was rather confounded when I had an issue with his house, which required I enter build/buy mode. To my aggravation, all of these bright glowing lines were all over the place making it so hard for me to see what I was doing, that I ended up going into My Library and downloading a copy of this lot over itself!

I could understand if this business of his was on the home lot. But it isn't. I specifically chose not to do it that way. One likes to go home after a hard day at the "office", so to speak. Plus, the man did not operate his tavern out of his home. And when he felt a need to take out a license for an Inn, he made certain to build it quite a distance from his farm.  He was totally bothered by strangers knocking on his door asking for lodging, hence the need to take out said license. I don't know, maybe he was grumpy?

At any rate, is there a way to be rid of these lines of demarcation? I do hope so. I am not inclined to scrap this save to start over, fresh, for a second time. Please, and thank you, in advance.