What should a roof cost estimate include beyond a calculator number?
Short answer. A real roof estimate lists the measured squares, layers to tear off, shingle line, underlayment, ice and water shield locations, drip edge, flashing, ventilation, decking allowance, permit and disposal. A calculator number has none of that, so use it only to check whether a written estimate is in the right neighborhood.
The line items to look for
- Measured squares and pitch, with the waste percentage stated.
- Tear-off and the number of layers.
- Shingle brand and exact product line, not just "architectural shingles."
- Underlayment type, synthetic or felt, over the whole deck.
- Ice and water shield in valleys, around chimneys, skylights and pipes; see ice and water shield in Georgia.
- Drip edge at eaves and rakes.
- Flashing: new step flashing, chimney work, new pipe boots. See roof flashing explained.
- Ventilation: ridge vent or other exhaust, and whether intake is adequate.
- Decking: a per sheet price for any replacement found during tear-off.
- Starter and ridge cap products.
- Permit, disposal, cleanup, and the warranty terms.
Red flags
A single lump sum with no detail. "Decking as needed" with no price. "Reuse existing flashing" without explanation. No mention of underlayment, which you can compare in synthetic underlayment vs felt. An estimate that changes dramatically depending on whether insurance is paying.
How to use the calculator number
If the written estimate is far from your calculator range, the difference should trace to something on your roof: steep pitch, extra layers, a chimney rebuild. If nobody can point to the reason, keep shopping.