Wall area, in squares
Siding is sold by the square, which is just 100 square feet. Get your net wall area, add waste, then divide by 100.
Wall area is the perimeter of the house times wall height, plus the triangular gable areas under any peaked roof. A house with a 160 ft perimeter, 12 ft walls and 400 ft² of gables is (160 × 12) + 400 = 2,320 ft². Take off the big openings, add 10 percent, and you are near 23 to 24 squares.
Material drives the waste factor and the cost
| Material | Installed cost / ft² | Waste | Lifespan |
|---|---|---|---|
| Vinyl | $4.50–8.00 | 10% | 20–40 yr |
| Aluminum | $5.50–10.00 | 10% | 30–40 yr |
| Wood | $8–15 | 10–15% | needs repaint 5–8 yr |
| Fiber cement | $6–12 | 12–15% | 50+ yr |
| Brick veneer | $5–15 | — | 100+ yr |
Fiber cement and complex layouts push waste higher. A plain rectangular house on the low end of each range keeps both material and labor down.
Trim is priced separately
- J-channel and trim wrap every window and door, so they are figured from opening perimeters, not from wall area. Sum the perimeters and add about 10 percent.
- Typical trim cost is $0.50 to $1.50 per linear foot depending on the material.
- House wrap (like Tyvek) goes on before the siding at roughly $0.10 to $0.30 per ft² and is required for a proper drainage plane.
Common questions
What is a "square" in siding?
A square is 100 square feet. Siding is ordered and priced by the square, so a 2,000 square foot house is 20 squares before waste. Divide your net wall area by 100 to get squares.
How much waste should I add for siding?
Ten percent for a plain rectangular house, 15 to 20 percent for one with many corners, dormers or gables. Fiber cement runs 12 to 15 percent because it is brittle and cracks when cut.
Do I subtract windows and doors?
Subtract large openings such as a garage door or picture window. Skip small windows and single doors — leaving them in gives a built-in cushion and covers offcuts, and many estimators do exactly that.
