FranklyTear-off layers and disposal
Removing one layer of composition shingle is straightforward. Removing two, or removing concrete tile and its battens, multiplies both labour hours and dump fees. If an estimate does not say how many layers are coming off, that is the first question to ask, because the answer can swing the price by thousands.
What happens when the deck is opened
Nobody knows the condition of the sheathing until the old roof is off. A fair estimate says so, and gives a written per-sheet price for replacement plywood. An estimate that stays silent on decking is not cheaper — it just moves that conversation to the day the crew finds rot, when you have no leverage.
Flashing, penetrations, and edge metal
Most roofs do not fail in the open field; they fail at chimneys, skylights, valleys, wall intersections, and pipe boots. Reusing old flashing is how a price comes down. It is also the most common reason a new roof leaks in its first winter. Confirm in writing which flashings are being replaced rather than reused.
Access, pitch, and the house itself
A single-storey ranch with a driveway beside it costs less to roof than a steep two-storey on a canyon lot in a hillside neighbourhood where material has to be carried. Steeper pitch means slower work and more fall protection. None of that is padding — but it should be explained, not just built into a round number.