Shiplap profile cross-sections — nominal vs actual vs net coverage width

No “1×6” covers 6″: rabbeted pine covers 5″, nickel-gap T&G covers 4⅝″, pattern T&G covers 5⅛″. Rows = wall span ÷ net coverage — always the exposed face, never the nominal size.

Source: Coverage per manufacturer listings (Lumber & Supply Co., UFP-Edge, Twin Creeks); worked-lumber patterns per PS 20-20

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What this diagram shows

Three wall cross-sections through a shiplap joint comparing the common profiles, each dimensioned with actual milled width in gray and net exposed coverage in blue. A traditional rabbeted pine 1×6 mills to 5-1/2 inches but its half-inch lap leaves only 5 inches of coverage. A nickel-gap tongue-and-groove 1×6 mills to 5-5/16 inches and covers 4-5/8 inches after the tongue and the 1/8-inch reveal. Tongue-and-groove pattern pine 1×6 mills to 5-3/8 inches and covers 5-1/8 inches with a tight reveal. No "1×6" covers 6 inches — rows or runs are solved as wall span divided by NET COVERAGE, the exposed face width, which varies by brand even at the same nominal size.

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    <img src="https://remodelcalculators.com/api/figure-embed/shiplap-profile-coverage" alt="Three wall cross-sections through a shiplap joint comparing the common profiles, each dimensioned with actual milled width in gray and net exposed coverage in blue. A traditional rabbeted pine 1×6 mills to 5-1/2 inches but its half-inch lap leaves only 5 inches of coverage. A nickel-gap tongue-and-groove 1×6 mills to 5-5/16 inches and covers 4-5/8 inches after the tongue and the 1/8-inch reveal. Tongue-and-groove pattern pine 1×6 mills to 5-3/8 inches and covers 5-1/8 inches with a tight reveal. No &quot;1×6&quot; covers 6 inches — rows or runs are solved as wall span divided by NET COVERAGE, the exposed face width, which varies by brand even at the same nominal size." width="800" height="500" style="width:100%;height:auto;border:0" loading="lazy">
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    Diagram: <a href="https://remodelcalculators.com/construction-diagrams/shiplap-profile-coverage" target="_blank" rel="noopener">Shiplap profile cross-sections — nominal vs actual vs net coverage width</a> — courtesy of <a href="https://remodelcalculators.com" target="_blank" rel="noopener">RemodelCalculators.com</a>
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