Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of building product maker Trex Company (NYSE:TREX) fell as much as 14.6% today after reporting earnings.

So what: First-quarter revenue fell 6.7% to $100.6 million and net income dropped 43% to $12.3 million, or $0.73 per share. Analysts were expecting a lot more, projecting $115.3 million in revenue and $0.93 per share in earnings.  

Now what: Management thinks the decking season is just off to a slow start, which makes sense considering the bad winter in the Midwest and Northeast this year. That's why they were confident enough to project $125 million in revenue for the second quarter, which is already more than one-third over. I think today's drop is actually a great buying opportunity because factors that affected the first quarter are one-time in nature and long-term the housing industry has a lot of upside to catch up with slow building in recent years.