Roofing is priced by the square — one hundred square feet of roof. Everything else is a multiplier on how many squares you have and what each one costs to cover.
Material is the biggest single line and the one everyone thinks about. Basic asphalt starts around $345 a square installed; natural slate can pass $3,000. That range is real and it is the first decision worth spending time on.
Pitch is the one people miss, and it moves the number twice. A roof is bigger than the ground it covers: a 12:12 pitch has forty-one percent more surface than its footprint, so you buy forty-one percent more material. Then, above about 6:12, a crew cannot stand unaided, so staging and harnesses go up and the pace comes down.
Shape is the next one. Every valley, hip, dormer and pipe is a cut, and every cut leaves offcut you paid for. A plain gable wastes around five percent. A cut-up roof with dormers and a turret wastes over twenty, and takes far longer per square.
Then there is what is already up there. Stripping an old roof runs a hundred to two hundred dollars a square per layer, and heavy materials like tile cost roughly double that to remove and haul. If you have two layers, most codes require a full strip.
None of this is secret and none of it is complicated. It is just that the trade has historically kept it behind a sales visit. It does not need to be, which is why our estimator shows you every line of it.
