There are a few variables that can affect installation time, including whether the roof is damaged, whether you need structural repairs before the crew can install a new roof, if there are weather-related delays and which type of materials you chose.  Of course the roof’s size and pitch (steepness) are commonly the two most relevant factors in determining how long a re-roofing job may take, in addition to the size of the crew available.   In most cases, the process is straightforward and can move along as fast as you and your contractor can complete each step.  For the most common sized homes with mild to moderate roof pitch, two to eight days is a common timeframe for a roofing project.  But again, there are numerous factors that can cause this to vary greatly.