Gather the house plan, roof drawings and photographs taken safely from ground level. Note the location, project type and preferred timing. Do not climb onto the roof to obtain measurements.
The house footprint is not the roof area. Pitch, eaves, dormers and level changes must be considered. The calculator only provides a geometric estimate for simple shapes.
A survey checks lengths, diagonals, slopes and junctions. For renovation, describe leaks and previous repairs. The final system is selected after the project is checked.