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Boards, posts, rails and screws for a lapped board fence.
With these inputs:
| Result | Value |
|---|---|
| Total boards | 429 |
| Boards needed (with waste) | 429 |
| Boards per linear ft | 2.67 |
| Boards vs a solid fence (×) | 1.22 |
| Gap in the back layer (in) | 3.5 |
| Posts | 20 |
| Rails | 57 |
| Screws (approx.) | 2832 |
| Board cost | $1,716 |
At a 1" lap this uses 1.22x the boards of a solid fence. The lap is the whole cost lever — 1" is the usual minimum, 2" is common, and only a half-width lap actually doubles the count.
A board-on-board fence has an under layer with gaps and an over layer centred on those gaps. Because each overlaid board laps its neighbours on both edges, the run advances by the board width minus one overlap for every board you hang. Change the overlap and the board count — and the cost — moves with it.
Advance per board = board width − overlap · Boards = ⌈(run ft × 12) ÷ advance⌉ × (1 + waste %)
Take the run in inches and divide by the board width minus the overlap. With 5.5 inch boards at a 1 inch lap that is 4.5 inches per board, or about 2.67 boards per linear foot — roughly 267 boards for a 100 ft run before waste. Add 10 percent for cuts and rejected boards.
Yes, and the overlap decides by how much. At a 1 inch lap on 5.5 inch boards it uses about 1.22 times the boards of a solid fence; at 2 inches about 1.57 times; only at a half-width lap does it genuinely double. Framing, posts and labour are the same, so the extra cost is narrower than the board count suggests.
One to two inches on a 5.5 inch board. One inch is the usual minimum because pressure-treated boards shrink as they dry, and a lap much under an inch can open into a visible sightline. Two inches buys insurance against shrinkage at the cost of about 28 percent more boards.
Board-on-board puts both layers on the same side, so one face looks layered and the other shows the rails. Shadow box alternates boards between the two faces, so both sides look the same and you can see through at an angle. Board count is the same for the same overlap; the difference is appearance and privacy.
Three for a 6 ft fence. The double layer roughly doubles the weight hanging on the rails compared with a solid fence, and a two-rail 6 ft board-on-board fence will sag between posts. Some builders add a fourth rail on 8 ft fences.
That is its whole purpose. A solid fence built from wet pressure-treated boards opens an eighth to a quarter inch gap at every joint as the wood dries. Board-on-board overlaps those joints, so shrinkage just narrows the lap instead of opening a hole.
A nominal 1x6, which actually measures 5.5 inches. Some builders mix a 1x6 under layer with a 1x4 (3.5 inch) over layer, which uses fewer board feet but needs a tighter under-layer spacing. Always calculate with the actual width, never the nominal one.
Yes, and it handles slopes better than panel fences. Rack the rails to follow the grade and hang each board plumb, letting the bottoms step down. Because the boards overlap, a slight variation between boards is invisible in a way it would not be on a solid fence.
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