When a final number is presented to a home or business owner for the cost of their new roof, plenty of clients wonder how the roofing contractor arrived at that number. Two main factors come in to play when calculating a bid: the cost of labor and materials needed for the job.

To determine labor costs, your roofer considers the pitch & height of the roof, the roof’s current condition, and accessibility to the job site. When a roof has a steep pitch or covers multi-story building, the job becomes more involved and workers may have to use harnesses for safety; special equipment could increase the bid. Another possible cost lies in the existing roof. In many situations, a new roof can be laid over top of the old roof. However if this has already been done several times, removing all the old layers and hauling it away can incur additional labor and disposal charges. Finally, your contractor will take into consideration how accessible the job site is for workers’ trucks and equipment, especially as material is delivered and hauled away. Remote sites, narrow driveways with low tree lines, or busy urban locations could drive up the final price.

The other main factor going into a bid is the materials necessary to complete the work. Some roofs require special attention, those with skylights or multiple chimneys for example, and therefore additional costs can result. Additional flashing and pan metal, the type of shingle chosen, and repair work to the subroof might also affect the final bid. Other factors taken into consideration include the time of year and the total square footage of the roof.

Always make sure you’re dealing with a reputable and licensed roofing contractor. Even if you purchase warrantied roofing products, those warranties can become void if an unlicensed contractor completes the work. Be sure to ask for credentials and references before signing off on the bottom line.