What roof tear-off reveals
Removing the old covering makes a part of the roof visible that a surface inspection cannot fully show. The exposed deck can change the replacement scope before new roofing goes on.
The deck supports the new roof
The roof deck provides the base for the covering and its attachment. Water entry can deteriorate wood beneath an apparently small opening, while older patches can conceal uneven or unsuitable support. The extent is not established until the relevant layers are visible.
During a tear-off replacement, the removed covering exposes the deck for evaluation and needed correction. Unsound material cannot become a suitable base simply by adding fresh underlayment over it.
Deck correction and covering are connected work
Damaged sheathing or boards need an agreed repair basis and suitable attachment. A replacement scope identifies how discovered wood damage is handled rather than pretending its exact extent is already known.
Structural framing changes are a separate question from replacing deteriorated sheathing. If the roof's support is compromised, that issue needs the appropriate assessment and coordination before covering work proceeds.
Roof replacement scope
Tear-off and recovery answer different questions
A recover retains an eligible existing assembly beneath new roofing. It does not offer the same direct view of all the deck below. Existing moisture, support, loading, layer limits and product requirements determine whether recovery is appropriate.
That does not make every roof a tear-off by default, or every sound-looking roof eligible for recovery. The decision follows the existing assembly and the rules for the proposed system.
The price changes when the work changes
Extra removal, damaged decking and complex wall or chimney connections add work beyond the base covering. A regional asphalt planning example assumes usable decking, so it cannot price undiscovered deterioration at an individual property.
Understanding that distinction makes a replacement budget more useful. The calculator helps with the measured roof area; the inspection and actual scope address the building.