Polycarbonate Roofing Installation: Step-by-Step Site Guide

This is a practical on-site reference for installation teams fitting a standing seam polycarbonate roofing system. It follows the correct sequence of operations and includes the checks that prevent the most common failure modes.

Note: This guide covers the general standing seam system installation logic. Always refer to the specific manufacturer's installation manual for the system being installed. This guide is intended as a site reference complement, not a replacement for system-specific documentation.

Phase 1: Pre-Installation Verification

Before any polycarbonate is touched, the structure must be verified.

Step 1.1 — Structural check

Confirm purlin spacing matches the approved installation drawing (measure at least 5 random spans — don't assume all bays are equal)
Check purlin levelness along the slope direction (high/low points of more than 5mm require correction)
Check purlin alignment in plan (purlins must be parallel — not converging or diverging)
Confirm minimum slope: 5° is the absolute minimum; 7° or more is preferred
Check that purlin ends are tied down at both ends of the structure

Step 1.2 — Accessory check

Count and verify all accessories against the delivery note and accessory schedule
Check panel length matches the project dimension (never assume factory length = design length)
Inspect first 10 panels for any transport damage, dimensional variation, or protective film damage
Confirm which side is the UV-protected top face (check film markings)

Phase 2: Cleat Installation

Step 2.1 — Cleat positioning

Mark cleat positions on purlins according to the installation drawing (cleats run along the standing seam of the panel, parallel to the slope)
Cleats must be positioned to fall exactly at the panel seam location — not at random intervals
For continuous cleat systems: cut cleats to panel length minus the thermal expansion clearance specified by the manufacturer (typically 5mm at each end)

Step 2.2 — Cleat fixing to purlin

Fix cleats to purlins using the specified fasteners — SS self-drilling screws for steel purlins, SS bolts for predrilled structures
Cleats must be fixed at maximum 500mm intervals along their length (or per manufacturer's requirement)
Check cleat alignment with a string line before fixing — crooked cleats mean crooked panels and connector engagement problems
Do not over-tighten fixings to the point that the cleat deforms

Phase 3: First Panel Installation

Step 3.1 — Starting panel placement

Place the first panel at the edge of the roof with the UV-protected face upward (film markings up)
The standing seam on one side of the panel engages the cleat — check that the seam clicks fully into the cleat grip-lock mechanism
At the eave end: leave a minimum 3mm gap between the panel end and any fixed stop in the eave trim (thermal expansion clearance)
At the ridge end: same gap required

Step 3.2 — End closure on starting panel

Apply aluminium tape across the full width of both the eave end and ridge end of the panel, covering all open cells
Fit the PC end cap over the connector body at both ends
Fit the aluminium U-profile over the taped end — the profile should sit flush against the panel face without forcing

Phase 4: Subsequent Panels

Step 4.1 — Panel interlocking

Place the next panel adjacent to the first, engaging the standing seam on its free side into the connector slot
Press the connector into position — it should click audibly when correctly engaged
Do not use excessive force; if a connector resists engagement, check that the panel edge is properly aligned and that no panel end is overhanging a fixed stop

Step 4.2 — Connector sequence check

At every purlin, press down on the connector to confirm it is seated against the cleat
A correctly installed connector is flush with the top of the standing seam and does not rock when pressed
If there is any visible gap between the connector underside and the cleat, the connector has not engaged properly — remove and re-seat

Step 4.3 — Progressing across the roof

Work from one edge to the other in a consistent direction
Do not skip panels or jump to non-adjacent panel positions
Do not remove protective film from installed panels until the area is complete

Phase 5: Ridge and Eave Closure

Step 5.1 — Ridge closure

At the ridge, fit the aluminium U-profile to close the upper panel ends (tape and end caps must already be fitted)
The ridge flashing laps over the U-profile by a minimum of 100mm
Fix the ridge flashing with the specified fasteners at maximum 400mm spacing
Apply compatible flexible sealant at the lap between ridge flashing and U-profile — do not use rigid epoxy

Step 5.2 — Eave closure

At the eave, the U-profile at the panel bottom must drain freely into the gutter
Do not seal the lower end of the U-profile — it must remain open for drainage
Fit the eave trim to close the visual gap between the panel and the gutter fascia

Phase 6: Wall Abutments and Penetrations

Step 6.1 — Wall abutments

At wall junctions, the wall flashing must lap over the top of the panel by a minimum of 150mm
The flashing must be fixed to the wall, not to the polycarbonate panel — polycarbonate moves thermally; a flashing fixed rigidly to both wall and panel will crack
Apply a bead of compatible sealant between the flashing and the wall surface
Use a kick-out profile at the lower edge of all wall flashings to direct water away from the wall cavity

Step 6.2 — Penetrations

For structural column or hanger penetrations through the roof plane, use purpose-designed penetration flashings
The flashing collar must be flexible or have a movement joint to accommodate thermal movement of the panel
Do not seal panel-to-column gaps with silicone alone — this will split within two years

Phase 7: Final Inspection

Before protective film removal and handover:

□ All connectors seated and flush
□ All cleats fixed at correct spacing
□ End tape and end caps fitted at all panel ends
□ U-profiles fitted at ridge and eave
□ Ridge flashing lapped and sealed
□ Eave trim fitted, lower U-profile drain point clear
□ Wall flashings fixed to wall (not to panel), kick-out profile fitted
□ All penetrations flashed
□ Protective film intact on all panels
□ No visible oil canning or panel deformation
□ No gaps or misalignments visible at connector joints
□ Slope verified at minimum 5°
□ Site is clean — no debris on panel surfaces

Remove protective film only after all work is complete and the site is clean.

Coxwell can provide system-specific installation manuals for all Coxwell standing seam systems. Contact your sales contact or download from coxwell.in.