"Mr. Murphy of New York", a short story by Thomas McMorrow; first published in the March 22, 1930 issue of The Saturday Evening Post. You may have read it in Groff Conklin's 1950 anthology Big Book of Science Fiction, or in Damon Knight's 1968 anthology One Hundred Years of Science Fiction. Any of these covers look familiar?
A committee of men has gathered to discuss the recent (2 weeks ago?) spontaneous collapse of a skyscraper. One of the men is soon established to be a dim, upper-class twit with nothing to contribute.
"Quite,' I said curtly, and readdressed myself to Cohen: "Were you in New York when the Americus Tower fell?"
"I had my residence on the roof of the Americus," interposed the futile Mr. Murphy, producing blue prints, "and the coziest home I ever lived in. If you'll give me your gracious attention now, Mr. Craig, I'll show you what I want you to build for me in the way of a residence atop your new Central Unit in Canabec, and I'll take a twenty-year lease at eighty thousand a year."
He was of just enough importance to us to be admitted to the fringes of our conference, but that wasn't Mr. Murphy's conception of his status. He had a great deal of inherited money.
Near the end of the story the twit reveals that he had had a narrow escape, since he lived in the penthouse suite (an entire floor) of the collapsed building, and had been in Europe on vacation when the collapse occurred.
"You weren't at home, I take it, Mr. Murphy," said Cohen soberly, "when the Americus fell?"
"Oh, I would have been killed!" expostulated Mr. Murphy. "As a matter of fact, gentlemen, I was at my shore home in Maine."
And he insists on telling the others that his wife accuses him of leaving the bath running when he left. The others realize that, since the apartment was sealed, the entire floor would have filled with water and caused the collapse due to its weight.
"If you were drawing your bath," I said sternly, "you must have stopped the water. And you think that, perhaps, you went away and left the water running."
"A mere surmise, Mr. Craig. But why are you so pressing? If you think that I should pay this bill even now—"
I drew a breath. "A hundred thousand cubic feet of water, gentlemen, weighs more than three thousand tons. In my opinion, though I'm no engineer, the steel frame designed by Hendricks would not have stood under a superimposed load of three thousand tons—not without buckling somewhere. If it would stand any such overloading, Hendricks didn't know his business. It's late in the day to reopen the investigation into the fall of the Americus Tower."
In this story we find what may be the earliest fictional mention of a pocket videophone:
"Now, gentlemen, please," breathed Mr. Bligh. "Do remember that I'm a thousand miles from home and haven't had any lunch yet. Well, I shall have to call up." He took out his pocketell. "Are you there? Billy calling . . . Hello, Molly! I just called you to say that I can't possibly get home— What's that, sweetheart? . . . Oh, no, no. . . . But I say that I am not! I am in New York in a conference. . . . Yes, business. . . . Why don't I— Now, Molly, how can you ask me to be so rude? . . . Oh, very well, my dear, in a moment." He turned to us, coloring, and said, "Will you permit?" We were married men ourselves; we smiled and got to our feet and bowed to his lady when she appeared; her eyes swept us vigilantly. "I'm sorry this had to happen, gentlemen," said Mr. Bligh, blanking her. "May we proceed now with our affair?"