Count the layers before you compare quotes
A roof that has been re-covered once has two layers of shingles, and the newer one was nailed straight through the older. Both come off together, so the crew moves more weight and pulls more nails for every square of roof. The site prices a second layer at about half again the cost of one, not twice, because both layers usually come off in the same pass and the setup, protection and clean-up are paid only once. Set the layer count in the roof replacement calculator to see the difference on a whole job.
You can usually count the layers yourself. Look at the roof edge along a gable end or at the eave, where the shingles overhang the drip edge: one layer shows a single thin edge, two show a thicker stacked edge, often with a slight step. A roof that looks lumpy across the field is another sign. If the bottom layer turns out to be wood shingles, mention it when you ask for quotes, because the boards under wood shingles were often laid with gaps and will need sheathing before asphalt goes on (see roof decking installation).
Layers also decide whether removal is optional at all. A new roof can go over a single existing layer in most places, but IRC section R908.3.1.1 does not allow a recover where there are already two or more layers, or where the existing roof is slate or tile. On a two-layer roof, tear-off is not a line you can decline.
Disposal is a weight problem
Old shingles are heavy for their bulk. A square of architectural shingle weighs roughly 240 to 340 pounds new (the shingle guide lists weights by grade), so even a modest house sends more than a ton to the landfill per layer, before the felt and nails. Roofing debris usually reaches a container's weight allowance before it looks full, and haulers typically charge by the ton past that allowance.
The estimate carries one 20-yard dumpster at $400 to $600, sized for a single layer on a roof like this one. A second layer or a bigger roof can mean a larger container or a second haul, so ask whether a quote includes the overage or leaves it as an extra. In parts of the country asphalt shingles are recycled into paving, and a hauler who sends them there will want the load kept free of wood and household trash.
Placement matters too. The dumpster goes as close to the eave as the driveway allows so debris drops straight in, and it should sit on boards over a soft lawn or new concrete. The tarps in the estimate ($80 to $160) cover beds and shrubs, the contractor bags take what gets swept from gutters and walkways, and the last hour of the job is a magnet rolled over the yard and drive for stray nails.
The bare deck gets inspected
Tear-off is the only time anyone sees the roof deck from above. Once the old nails are pulled or driven flush, the crew walks it looking for sheathing that gives underfoot, plywood with its layers separating, OSB swollen at the edges, and dark staining around old vents, chimneys and along the eaves. Anything soft is cut out and replaced before underlayment goes down.
That replacement is not in this price, and nobody can price it from the ground, because the bad sheets cannot be counted until the shingles are off. The way to keep it fair is a per-sheet rate written into the contract before work starts, with each replaced sheet photographed. Roof decking repair covers what that work costs and what rots a deck in the first place.
Why removal is sold inside a replacement
Few homeowners buy a tear-off on its own, and plenty of roofers would rather not sell one. A crew strips a section, inspects it and covers it with underlayment the same day, so the house is never left open overnight. Split removal from installation and there is a gap where nobody answers for an open roof, and a roofer who never saw the deck has reason to exclude it from the warranty. Removal therefore shows up as a line inside a roof replacement quote, usually priced per square for each layer.
Standalone removal does happen: before a teardown, before structural work on the rafters, or when a homeowner strips the roof to save labor and hires a roofer for the rest. Agree that last arrangement with the roofer first, including who covers the deck if rain arrives early.
When you line up replacement quotes, find the tear-off in each and check four things: how many layers it assumes, whether disposal and any weight overage are included, whether decking has a per-sheet price, and whether ground protection and the nail sweep are listed. A bid well under the others usually leaves one of them out.