How we put a price on a roof: the method, in plain English

A roof is the clearest example of why one number is useless. The same 1600 sq ft house can be quoted $9,000 or $20,000 honestly, because four things move independently.

1. What comes off

Re-shingling over one existing layer is a different job from a full tear-off. Two layers means a strip and re-deck line item, and it is where most “surprise” change orders come from.

2. What goes back on

Three-tab and architectural shingles are priced per square foot, and the gap between them is larger than most homeowners expect once underlayment and ice-and-water shield are added at the eaves.

3. Access

Pitch, height, and whether a dumpster can sit at the house. This is the variable a national figure cannot see, and the reason we publish a range instead of a number.

4. Labour, by city

We take national trade wage data and apply a metro factor. That is the whole trick and the whole limitation: it captures that San Francisco labour costs about 42 percent more than the national average, and it cannot tell you about your specific roof.

So use the range to ask better questions, not to accept a number.