Builders FirstSource (BLDR) could be a solid addition to your portfolio given a notable revision in the company's earnings estimates. While the stock has been gaining lately, the trend might continue since its earnings outlook is still improving.The rising trend in estimate revisions, which is a result of growing analyst optimism on the earnings prospects of this construction supply company, should get reflected in its stock price. After all, empirical research shows a strong correlation between trends in earnings estimate revisions and near-term stock price movements. Our stock rating tool -- the Zacks Rank -- is principally built on this insight.The five-grade Zacks Rank system, which ranges from a Zacks Rank #1 (Strong Buy) to a Zacks Rank #5 (Strong Sell), has an impressive externally-audited track record of outperformance, with Zacks #1 Ranked stocks generating an average annual return of +25% since 2008.Consensus earnings estimates for the next quarter and full year have moved considerably higher for Builders FirstSource, as there has been strong agreement among the covering analysts in raising estimates.The chart below shows the evolution of forward 12-month Zacks Consensus EPS estimate:12 Month EPSCurrent-Quarter Estimate RevisionsFor the current quarter, the company is expected to earn $1.82 per share, which is a change of +44.44% from the year-ago reported number.Over the last 30 days, the Zacks Consensus Estimate for Builders FirstSource has increased 86.05% because five estimates have moved higher compared to no negative revisions.Current-Year Estimate RevisionsThe company is expected to earn $8.22 per share for the full year, which represents a change of +173.09% from the prior-year number.In terms of estimate revisions, the trend for the current year also appears quite encouraging for Builders FirstSource. Over the past month, two estimates have moved higher compared to no negative revisions, helping the consensus estimate increase 31.17%.Favorable Zacks RankThanks to promising estimate revisions, Builders FirstSource currently carries a Zacks Rank #1 (Strong Buy). The Zacks Rank is a tried-and-tested rating tool that helps investors effectively harness the power of earnings estimate revisions and make the right investment decision. You can see the complete list of today's Zacks #1 Rank (Strong Buy) stocks here.Our research shows that stocks with Zacks Rank #1 (Strong Buy) and 2 (Buy) significantly outperform the S&P 500.Bottom LineWhile strong estimate revisions for Builders FirstSource have attracted decent investments and pushed the stock 19.4% higher over the past four weeks, further upside may still be left in the stock. So, you may consider adding it to your portfolio right away. Zacks' Top Picks to Cash in on Artificial Intelligence In 2021, this world-changing technology is projected to generate $327.5 billion in revenue. Now Shark Tank star and billionaire investor Mark Cuban says AI will create "the world's first trillionaires." Zacks' urgent special report reveals 3 AI picks investors need to know about today.See 3 Artificial Intelligence Stocks With Extreme Upside Potential>>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Builders FirstSource, Inc. (BLDR): Free Stock Analysis Report To read this article on Zacks.com click here.