Measuring your walls
Siding is sold by the square, which covers 100 square feet of wall. To find how many squares you need, measure each wall and gable and subtract the openings.
- Wall area = perimeter of the house × wall height to the eaves
- Gable area = gable width × gable height ÷ 2, for each triangular gable
- Net area = wall area + gable area − windows and doors
- Squares to order = net area × (1 + waste allowance) ÷ 100
Worked example
A one-story house has a 160 ft perimeter, 10 ft walls and two gables 30 ft wide and 7 ft high. Windows and doors total 200 sq ft. You add 10% for waste, and siding costs $150 a square.
- Walls: 160 × 10 = 1,600 sq ft.
- Gables: 2 × 30 × 7 ÷ 2 = 210 sq ft.
- Net area: 1,600 + 210 − 200 = 1,610 sq ft.
- With 10% waste: 1,771 sq ft, or 17.7 squares.
- At 2 squares per box: 9 boxes, for about $2,657 of siding.
- Starter strip: about 160 ft, the length of the perimeter.
How much waste to allow
| House shape | Waste allowance |
|---|---|
| Simple rectangle, few openings | 10% |
| Several gables, dormers or corners | 12 to 15% |
| Many windows, bump-outs or patterns | 15 to 20% |
Small window areas under about 10 sq ft are often not subtracted, because trimming around them wastes as much material as they save.
Siding materials
| Material | Typical lifespan | Notes |
|---|---|---|
| Vinyl | 20 to 40 years | Low maintenance and low cost |
| Fiber cement | 30 to 50 years | Fire resistant; heavy; needs painting |
| Engineered wood | 20 to 30 years | Wood look; lighter than fiber cement |
| Wood (cedar, pine) | 20 to 40 years | Needs regular staining or painting |
| Metal (steel, aluminum) | 30 to 50 years | Durable; can dent |
Trim and accessories
Beyond the panels, plan for J-channel around windows and doors, outside and inside corner posts, starter strip, soffit and fascia, house wrap, and corrosion-resistant nails. Accessories are sold by the piece, typically 10 to 12.5 ft long, so measure each run.
Check with your local building department before starting: many towns require a permit to replace siding, and some neighborhoods or historic districts limit materials and colors.