Board-on-Board vs Shadowbox: Coverage and Sightlines

Continuously lapped boards advance by board width minus overlap. A backer-and-cover fence instead puts cover boards over internal gaps in a base row. Shadowbox alternates boards on opposite sides of rails, usually with one face shifted relative to the other. These arrangements cannot share one universal boards-per-foot constant.

A straight-on elevation can hide gaps in a shadowbox fence while angled views remain open. Check a small mockup before treating a front-view overlap as complete privacy. Rail thickness and distance between faces influence the sightline.

For a 96 in field with 6 in boards and 1 in continuous lap, count = 1 + ceil(90 / 5) = 19 boards. For a shadowbox example with 6 in boards and a 6 in same-face gap, pitch = 12 in. Face A starts at 0, 12, …, 84 in and needs eight boards; face B starts at 6, 18, …, 90 in and also needs eight. Total is sixteen, with zero overlap in the front projection.

Reducing the same-face gap increases overlap and may increase board count. The tool counts footprints that intersect the field, including a final piece requiring a cut.

Decide how both ends meet posts and how top trim or capping is handled. A supplier may require extra edge pieces, a different face offset, or specific fasteners. Use the appropriate calculator mode, then add a separate purchasing allowance rather than hiding reserve material in the geometry. Structural spacing, post size and foundations need the selected system’s project specification.