I have to place a bid on installing patio stone but I don't know how to bid it. The area needs to be graded (by hand) and it's 480 sq ft. He wants to use a stone that is 16x16 inch. The grading alone will probably take at least a day since it needs a lot of prepping. I have an employee who has 10 yrs experience doing this type of work but has no expierence on placing estimites. He did landscaping for another company. He is the one that told me it would take about a day to grade and prep the ground. So basically I need help charging for the labor. Do I charge by the sq ft or by the hour?