# Roof Sheathing Calculator

Boards by sheet, battens by metre, nails by spacing - all three at once.

- Page: https://jianzhujisuan.com/en/roof-sheathing
- Category: Construction (https://jianzhujisuan.com/en/c/construction)
- Chinese version: https://jianzhujisuan.com/zh/roof-sheathing.md
- Data checked: 2026-10-25

## Quick result

With the default inputs (Sloped roof area 115.5 m², Board width 1.22 m, Board length 2.44 m, Waste 8%, Batten spacing 0.34 m, Nail spacing 0.15 m): **Boards incl. waste 43 sheets**

## Inputs

| Parameter | Type | Default | Unit | Note |
|---|---|---|---|---|
| Sloped roof area | number | 115.5 | m² |  |
| Board width | number | 1.22 | m |  |
| Board length | number | 2.44 | m |  |
| Waste | number | 8 | % |  |
| Batten spacing | number | 0.34 | m |  |
| Nail spacing | number | 0.15 | m |  |

## Formula

- **Board area**: a = width × length
- **Boards net**: n = ⌈As / a⌉
- **With waste**: N = ⌈n × (1 + waste)⌉
- **Batten length**: L = As / batten spacing
- **Board nails**: n = As / spacing²
- **Batten nails**: nb = L × 3

## Worked example

115.5 m² sloped, 1220×2440 mm boards, 8% waste, 340 mm batten spacing, 150 mm nail spacing: 2.977 m² per board, 39 boards net, 43 with waste, ~340 m of batten, ~5133 board nails plus ~1019 batten nails, about 6152 in total.

## Questions

### Why is sheathing waste higher than wall waste?

Because boards are laid on the slope and there are far more cuts: at the ridge, at the eaves, at valleys where two planes meet, around dormers and at verge closures. Every cut wastes part of a board and the offcuts are rarely usable. Use 8% for a simple mono-pitch or gable roof, 12-15% for a hip roof or one with dormers, and up to 20% for very complex shapes. Order a couple spare - a second delivery means waiting, plus batch and colour differences.

### How is batten spacing set?

By the effective tile length, not by habit. A 420 mm tile with an 80 mm head lap has a 340 mm effective length, so the battens must be at 340 mm: wider and the tiles are not held and will lift in wind, narrower and you waste material and add cost. The first batten at the eaves is set from the tile overhang (normally 50 mm) or the first course will not line up with the rest. The top batten at the ridge is set separately so the ridge tiles lap evenly on both sides.

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