This week, the overall grades of three Construction and Engineering stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

This week, URS Corp. (NYSE:URS) falls to a D (“sell”), worse than last week’s grade of C (“hold”). URS provides engineering, construction and technical services to the power, infrastructure, federal and industrial and commercial market sectors. In Portfolio Grader’s specific subcategories of Cash Flow and Margin Growth, URS also gets F’s. To get an in-depth look at URS, get Portfolio Grader’s complete analysis of URS stock.

Slipping from a C to a D rating, MasTec Inc. (NYSE:MTZ) takes a hit this week. MasTec, Inc. is a Florida Corporation. The Company is a specialty contractor operating mainly throughout the United States and across a range of industries. As of Oct. 4, 2012, 11.4% of outstanding MasTec Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of MTZ stock.

The rating of Orion Marine Group (NYSE:ORN) slips from a C to a D. Orion Marine Group operates as a marine specialty contractor serving the heavy civil marine infrastructure market. The stock gets F’s in Equity, Cash Flow, and Margin Growth. The stock price has dropped 4.3% over the past month, worse than the 3.2% increase the S&P 500 has seen over the same period of time. For a full analysis of ORN stock, visit Portfolio Grader.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.