All successful roof projects require that the installers adhere to proper application methods. Improper workmanship contributes to a decrease in the roof systems service life. All types of roof systems - both steep-slope and low-slope applications - are prone to potential workmanship errors. In the case of steep-slope shingle applications, there are a number of common mistakes that should be avoided to ensure a long service life. A successful roofing project and satisfied client can be achieved if these common mistakes can be avoided in the field.