Siding is measured in "squares" — each square covers 100 sq ft of wall area. Accurate takeoffs require measuring total wall area, adding gable triangles, subtracting doors and windows, and then adding waste factor for cuts and fitting.
The Formula
Gross wall area = Perimeter × Wall Height + Gable area (½ × width × peak height × number of gables). Net area = Gross area – Door openings (21 sq ft each) – Window openings (15 sq ft each). Squares = Net area with waste ÷ 100.
Vinyl vs. Hardie Board
Vinyl siding — $2–$4/sq ft material, lightweight, easy to install, 20–40 year lifespan, minimal maintenance
Hardie (fiber cement) — $4–$9/sq ft material, fire-resistant, termite-proof, 30–50 year lifespan, needs painting every 10–15 years
Wood siding — $5–$12/sq ft material, natural aesthetic, requires staining/painting every 3–7 years, susceptible to moisture and insects
Hardie board costs more upfront but may save money long-term due to lower maintenance costs
What Is a "Square" of Siding?
One square = 100 square feet of siding coverage. Manufacturers package siding by the square, so this is the standard ordering unit. Always round up to the next full square when ordering.
Trim & Accessories
Starter strip — runs along the bottom of all walls (total perimeter length)
J-channel — frames all doors, windows, and where siding meets soffit. Calculate the perimeter of each opening.
Inside corners — one piece per inside corner, height of wall
Outside corners — one piece per outside corner, height of wall
Don't forget utility trim, undersill trim, and F-channel at the soffit line
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