What happened

Shares of building supplies distributor Gibraltar Industries (NASDAQ:ROCK) are plunging today, down 12% as of 2:15 p.m. EDT.

So what

Considering that it's earnings season on Wall Street, you might suspect that an earnings report had something to do with why Gibraltar is sinking like a rock -- and you'd be right. Gibraltar reported its fiscal Q1 2017 earnings results this morning, and the news was not great.

Year over year, Q1 sales declined 13%, to $207 million, and profits tumbled 57%, to $0.12 per diluted share. Analysts had forecast sales of $209.9 million, which means that Gibraltar's results "missed estimates." Analysts also posited per-share profits of $0.21 per share.

That right there tells you why investors were upset with the results.

Stock chart falling through floor.

Gee! I wonder why Gibraltar stock is going down so much? Image source: Getty Images.

Now what

Looking ahead, Gibraltar CEO Frank Heard expressed hope that "short-term challenges" in Q2 will give way to "strong top- and bottom-line growth in the third and fourth quarters" of this year. Nevertheless, given that Q2 has done some damage to the business, Heard felt it necessary to revise Gibraltar's full-year guidance downwards.

As of today, Gibraltar expects that sales for this year will decline 2% to 3% to somewhere between $970 million and $980 million. Earnings, likewise, will fall short of last year's $1.67 in per-share profits, and also represent a markdown from previous guidance. By year end, Heard says the company will have earned only somewhere between $1.37 and $1.50 per share.

Long story short: If all goes as planned, Gibraltar's current stock price represents about a 22.8 times multiple on the best-case scenario for this year's profits -- and this in a company that's shrinking, not growing, earnings.

No wonder investors are dumping the stock.