What goes under shingles — the asphalt roof assembly from the deck to the ridge cap

What’s under the shingles, eave to ridge: roof deck, drip edge, an ice-and-water shield that must reach at least 24″ inside the warm wall line, underlayment lapped over it, a starter course, the overlapping field shingles, and the ridge cap. Each course covers the nails of the one below.

Cross-section up a roof slope showing the layers of an asphalt shingle roof from the deck to the ridge. From the bottom up: the wood roof deck (sheathing), a metal drip edge at the eave, an ice-and-water shield membrane that runs from the eave to at least 24 inches inside the exterior wall line to stop ice-dam leaks, synthetic underlayment lapped over the top of the ice barrier, a starter course along the eave that seals the first row, the field shingles installed in overlapping courses so each course covers the nail line of the one below, and a ridge cap that closes the peak. The ice barrier extending past the wall line is dimensioned because the IRC requires it in cold climates. — Source: IRC R905.1.2 (ice barrier 24″ inside wall line) / R905.2 / ASTM D3462; NRCA

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Cross-section up a roof slope showing the layers of an asphalt shingle roof from the deck to the ridge. From the bottom up: the wood roof deck (sheathing), a metal drip edge at the eave, an ice-and-water shield membrane that runs from the eave to at least 24 inches inside the exterior wall line to stop ice-dam leaks, synthetic underlayment lapped over the top of the ice barrier, a starter course along the eave that seals the first row, the field shingles installed in overlapping courses so each course covers the nail line of the one below, and a ridge cap that closes the peak. The ice barrier extending past the wall line is dimensioned because the IRC requires it in cold climates.

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    Diagram: <a href="https://remodelcalculators.com/construction-diagrams/shingle-roof-layers" target="_blank" rel="noopener">What goes under shingles — the asphalt roof assembly from the deck to the ridge cap</a> — courtesy of <a href="https://remodelcalculators.com" target="_blank" rel="noopener">RemodelCalculators.com</a>
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