How roof replacement cost is calculated

A roof quote looks like one number. It is really six numbers stacked — and knowing the stack is how you tell a fair quote from a padded one.

1. Materials (the covering)

Priced per "square" (100 sq ft of roof). Architectural asphalt runs roughly $550–$750 per square installed nationally in our model; standing-seam metal $1,200–$1,800. The covering is the single biggest lever on the total, which is why our calculator is organised by material first.

2. Tear-off and disposal

Removing the old roof and landfilling it. Included in our standard range for one layer; each extra existing layer adds roughly $0.75–$1.25 per sq ft. If a quote skips tear-off entirely, it is an overlay quote — cheaper, and a different job (see tear-off vs overlay).

3. Labour

Roughly 45% of the job. Roofers earn a national mean of $27.95/hr (BLS OEWS, May 2025), from about $22.69/hr in Texas to $37.33/hr in Illinois. That gap is why the same roof costs ±15% by state — and why our model uses wages, not vibes, for the local adjustment.

4. Pitch and complexity

Steep roofs are slower and need more safety equipment; valleys, dormers and multiple facets add cuts and waste. Expect +10–25% over a simple gable of the same area. Two-storey access adds a smaller amount.

5. Underlayment, flashing and ventilation

Synthetic underlayment or ice-and-water shield (required at eaves in cold climates), new flashing at chimneys and walls, drip edge, ridge venting. Legitimate quotes itemise these; "miscellaneous" lines that approach the material cost are a question to ask, not a line to pay blindly.

6. Permits, decking and surprises

Most jurisdictions require a re-roof permit (fees vary locally — ask your contractor to show the permit receipt rather than accepting a round number). Rotten decking is replaced per sheet and is the most common legitimate day-of extra; get the per-sheet price in writing before tear-off day.

Checking a quote

Divide the quote by your roof area: the per-square-foot figure should land inside (or explainably outside) the range for your material and state on your city page. Then check the quote names the shingle/metal product, the tear-off, the underlayment and the flashing — a quote that is one line and one number is not a quote you can compare.