From footprint to squares
A roofing square is 100 square feet of roof surface. Because a pitched roof is longer than the footprint it covers, the footprint is multiplied by a pitch factor: about 1.118 at 6/12, 1.302 at 10/12 and 1.414 at 12/12. Waste is then added for cuts at hips, valleys, dormers and the connected ells common on older Maine farmhouses.
Why the ice-barrier line matters here
Building codes in cold climates call for an ice barrier at the eaves that runs from the edge to at least 24 inches inside the exterior wall. On a steep roof with a deep overhang that can take two or three courses of membrane, not one. When a roof is replaced after an ice dam or wind loss, check that the estimate prices the full ice-barrier area, drip edge and any required underlayment. Those lines are easy to leave short.
- Compare the squares here with the roof report on the estimate; a gap of more than a few squares is worth asking about.
- At 8/12 and steeper, look for steep-roof labor charges. At two stories, look for high-roof charges.
More on winter roof claims: ice dam and snow load appraisal and roof and hail claims.
Questions about this tool
Is this as accurate as a measurement report?
No. Aerial or field measurements capture every facet, valley and dormer. This converter is a reasonableness check against the estimate.
Why does the tool assume two eaves?
It treats the footprint as a simple gable with eaves on the two long sides. Hip roofs have eaves on all sides, so add the extra length when you compare.
What waste factor should I use?
Plain gables run around 10%. Roofs with dormers, ells and valleys often need 13% to 18%. Your estimate should state the waste it used.