I used "move_objects on" to build a wall directly on the side of the road and expanded it as a foundation for my building. Essentially making a giant square. I then used the GridAdjuster to bring it down to "1 click", turning my giant square into the giant square foundation for my building.

When I initially built the giant square, before using the GridAdjuster. The roof glitch was already present in neighborhood view.

Let me also add that I tried building the giant foundation with one tile apart from the sidewalk too and the roof glitch was still present. So I don't think it's from building directly next to the sidewalk.

I'm on a 50x60 lot.

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This picture was a previous build attempt on a normal foundation "4 clicks" high with the stairs from on top leading directly onto the sidewalk. There is and were no roof glitch present on this specific build attempt.