Board-on-Board Fence Calculator — Privacy Fence Materials
A board-on-board fence staggers boards on alternate sides of the rails for full privacy while still allowing airflow. Enter your fence length, board size and overlap to calculate total boards, posts, rails and concrete.
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Boards on both faces of the fence combined
- 1
Board pitch
0.14 − 0.038 m = 0.102Centre-to-centre spacing between adjacent boards on one face. - 2
Boards per face
⌈30 ÷ 0.102⌉ + 1 = 296Ceiling rounds up so the full length is covered; +1 caps both ends. - 3
Total boards (both faces)
2 × 296 = 592
How does this calculator work?
For a board-on-board fence, each face needs ceil(length ÷ (boardWidth − overlap)) + 1 boards; double it for both faces. Posts = ceil(length ÷ postSpacing) + 1. Rails = bays × 2 or 3 by fence height. Budget 0.05 m³ of concrete per post. Typical overlap is 25–38 mm.
Formula
How this is calculated
In a board-on-board (also called shadowbox) fence, one set of boards is nailed to the front of the rails and a second set is nailed to the back, each offset by half a board width so they interleave. The centre-to-centre pitch between boards on one face equals boardWidth − overlap; a larger overlap creates a denser, more private fence but uses more lumber. The number of boards per face is the fence length divided by the pitch, rounded up, plus one extra board to cap both ends. Doubling this gives the total board count for both faces.
Posts follow the same logic as any fence: bays = ceil(length ÷ postSpacing), posts = bays + 1. Rails run between posts; fences 1.2 m and under use 2 rails per bay, taller fences use 3 for rigidity. Post concrete is budgeted at 0.05 m³ per post — enough for a 250 mm wide hole roughly 600 mm deep.
All values use metres. Typical board widths are 100–150 mm and overlaps 25–50 mm (about 25–35% of board width). A board-on-board fence uses roughly twice the boards of a standard picket fence at the same spacing, but delivers full privacy from any viewing angle.
Frequently asked questions
An overlap of 25–38 mm (about 25–35% of the board width) blocks sightlines at all angles, including when someone walks past. More overlap increases privacy but raises material cost. Less than 20 mm may leave gaps visible at oblique angles.
Yes. Because boards are attached to both sides of the rail, the fence is stiffer and distributes wind load more evenly. The extra lumber mass also reduces panel flex and adds to the fence's effective lifespan.
Add 10–15% to the board count to allow for defects, off-cuts and measurement errors. The post and rail counts are exact minimum quantities; buy a couple of spares in case of damage during installation.
TG we-Calculate Editorial Team. (2026). Board-on-Board Fence Calculator — Privacy Fence Materials [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/board-on-board-fence-calculator
TG we-Calculate Editorial Team. "Board-on-Board Fence Calculator — Privacy Fence Materials." TG we-Calculate. 2026. https://we-calculate.com/calculator/board-on-board-fence-calculator.
TG we-Calculate Editorial Team, "Board-on-Board Fence Calculator — Privacy Fence Materials," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/board-on-board-fence-calculator
@misc{wecalculate_board_on_board_fence_calculator, title = {Board-on-Board Fence Calculator — Privacy Fence Materials}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/board-on-board-fence-calculator}}, year = {2026}, note = {TG we-Calculate} }
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