Deck Prep & Underlayment: the full procedure

Prepare the exposed deck and install the underlayment and ice-dam protection that form the secondary water barrier.

• Applies to: Crew
• Frequency: Per replacement job
• Scope: Covers deck readiness and underlayment/ice-and-water installation to manufacturer and NRCA guidance. Deck structural repairs, ventilation code, and ice-dam zone determinations DEFER to a licensed roofer, local code, and the safety plan; all height work follows OSHA fall-protection standards.

What you need

• Underlayment (synthetic or No. 15 felt)
• Self-adhered ice-and-water membrane
• Drip edge
• Cap nails/staple gun
• Utility knife
• Chalk line

The procedure, step by step

1. Confirm deck is sound and dry — Verify all flagged decking has been addressed by the licensed-roofer decision and the surface is clean, dry, and fastener-free before covering.
2. Install eave drip edge — Set metal drip edge at the eaves under the ice-and-water per the install sequence; rake drip edge timing follows manufacturer guidance.
3. Apply ice-and-water at vulnerable areas — Install self-adhered membrane at eaves, valleys, and penetrations; in cold climates extend it a minimum of 24 inches inside the warm-wall line per NRCA, with exact zone set by local code.
4. Run underlayment up the field — Lay underlayment horizontally in shingle fashion, lapping a minimum of 2 inches on side laps and 4 inches on end laps per NRCA.
5. Fasten to hold pattern — Secure with cap nails or staples at the manufacturer-specified pattern so it stays put until shingles cover it.
6. Detail valleys and penetrations — Weave or line valleys per the chosen method and seal underlayment around pipes, chimneys, and vents.
7. Set rake drip edge — Install rake drip edge over the underlayment per manufacturer sequence.
8. Snap layout lines — Chalk horizontal and vertical control lines for straight, square shingle courses.

Quality check before you finish

• Deck confirmed sound (per licensed decision), dry, and clean before covering
• Ice-and-water at eaves/valleys/penetrations per NRCA and local code
• Underlayment laps meet 2 in side / 4 in end minimums
• Drip edge installed in correct sequence at eaves and rakes
• Fastening pattern matches manufacturer spec
• No wrinkles, fishmouths, or exposed deck
• Layout lines snapped square to the roof

This is a free, source-anchored standard operating procedure (SOP) you can print and hand to staff. It documents the work sequence for a Roofing business — not safety or regulatory rulings, which defer to the cited authorities, the applicable code, and your own health-and-safety plan. Open the tool above to print it, toggle ink-saver, or (with a free ToolFluency Business account) edit it to match your own workflow.

Sources

• NRCA (nrca.net)
• Owens Corning installer guidance (owenscorning.com)
• ARMA (asphaltroofing.org)