What to measure for siding, and what each number is for

Siding prices off wall area, but the wall area you bill is not the wall area you measure. What you deduct, and what you deliberately don't, is most of the skill.

The deduction rule that catches people

Small openings don't come off. The common convention is to deduct only openings above roughly 10 square feet — a picture window or a garage door, not a bathroom window. The reason is practical: you still cut a full panel to fit around a small window, so the material is consumed whether or not the hole is there.

Deduct every opening and you'll come up short on material on every job. Deduct none and you'll lose bids on houses with a lot of glass.

Openings cost trim, not just deductions

Every window is a perimeter of J-channel or trim. Two houses with the same wall area can differ by hundreds of dollars because one has fourteen windows and the other has six. Count openings as a number in their own right — it drives a line that square footage alone can't see.

Gables are where the labor hides

Gable area is real square footage, but it is also height. The same 200 square feet is a different job at ground level than it is at the top of a two-storey gable end needing staging. If your labor is one rate per square, high work is quietly underpriced — which is an argument for a separate line rather than a fudged area.

Measure per elevation, not per house

Front, back, left, right, each recorded separately. It costs a few minutes and it means a mid-job change — the customer wanting board and batten only on the front — is a small edit rather than a re-measure.

Once these are on the report, a package turns them into panels, starter, corner posts, J-channel and labor without you touching a calculator.