Installation begins with deck inspection. We verify sheathing is sound, flat, and fastened to code. Warped or water-damaged sheathing is replaced before underlayment goes down.
The deck must be dry. Moisture trapped under metal roofing accelerates corrosion from the interior.
Underlayment and Ice-and-Water Shield
We install a high-temperature synthetic underlayment rated for metal roofing. Standard felt underlayment degrades under the heat buildup between metal panels and the deck. Synthetic underlayment resists UV exposure during the installation window and provides a secondary water barrier if a panel seam fails.
Ice-and-water shield goes at all valleys, eaves, and penetrations. Miami doesn't see ice dams, but wind-driven rain under hurricane conditions can force water upslope past the panel laps. The self-adhering membrane seals around fasteners and transitions.
Panel Layout and Fastening
Standing-seam panels run from ridge to eave in continuous lengths when the roof slope allows. Panels longer than 40 feet require expansion joints to accommodate thermal movement. Galvalume expands and contracts with temperature swings, and a rigidly fastened long panel will buckle or pull fasteners.
Concealed clips fasten to the deck at 12 to 24 inches on center, depending on the panel manufacturer's specifications and the Miami-Dade NOA requirements. The clip slides into the panel's seam channel, and the adjacent panel snaps or mechanically seams over the clip. The fastener never penetrates the panel face.
Mechanically seamed systems use a portable seaming tool to fold the two panel edges together in a double-lock seam. The seam is weather-tight without sealant. Snap-lock systems rely on the interlocking panel geometry; we apply a bead of sealant at the snap joint on roofs below 4:12 pitch to prevent wind-driven rain infiltration.
Trim and Flashing
All trim (ridge caps, eave drip edges, rake edges, valley flashings) is fabricated from the same galvalume substrate as the panels or from a compatible metal (aluminum or stainless steel). Dissimilar metals in direct contact cause galvanic corrosion; we isolate incompatible metals with butyl tape or plastic separators.
Chimney and wall flashings are step-flashed and counter-flashed. The step flashing weaves under each panel course and laps up the vertical surface; the counter-flashing embeds into a reglet or surface-mounts over the step flashing with sealant. Penetrations (vents, pipes, HVAC curbs) receive custom-fabricated boots or curb flashings sealed with high-grade polyurethane or silicone.
Final Inspection
We walk the roof end-to-end before the final invoice. Every seam is checked for alignment and lock engagement. Every fastener is checked for proper torque. Over-driven screws compress the clip and restrict thermal movement; under-driven screws allow panel lift.
Every transition is checked for sealant continuity and proper lap direction.
The installation meets NRCA standards and the manufacturer's published guidelines. We hold NRCA membership, and our crews are trained to the technical requirements that galvalume roofing demands in South Florida's wind and corrosion environment.