Its a myth.
Please read the Humber Bridge Statistics
The bridge towers are 36mm (1.4 inches) further apart at the top than the bottom to take account of the curvature of the earth.
However this is actually addressed in the wiki.
It transpires that no one has ever actually measured the distance to confirm it, and that whilst the bridge should allow for curvature, its only a theory.
A round earther actually wrote to the Humber bridge for clarification. Here is the reply he got
There is the mail address [email protected] on page http://www.humberbridge.co.uk/administration.php and everyone can write and ask about the matter as I did. And the answer was following:
There is no evidence of this, unfortunately, it is merely a theoretical
and, I have been told, rather inprecise calculation.
Yours sincerely
Peter Hill
General Manager & Bridgemaster
Humber Bridge Board
Ferriby Road
Hessle
East Yorkshire
HU13 0JG
Many of the older RErs will remember Zork. I didn't just make him up. He was a pain in the butt for ages. But fell flat on his face with this.
Conclusions: RET expects buildings to account for earth's curvature. However its just theory, there is no evidence to support this.
You may also ask your civil engineering friend if they use tools like laser plumb lines when they build skyscrapers. If this is the case and the earth is round, this means the top floors of skyscrapers would have more sq.f floor space as the walls progressively splay outwards. Ask your friend if they charge more in rent for the extra floor space in skyscrapers, the higher you go. (They don't and advertised floor space is always the same on all floors in a 'square' skyscraper).
A flat earth really is the only sensible conclusion.